CN110761795A - Construction method of shallow tunnel in loess gully - Google Patents
Construction method of shallow tunnel in loess gully Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D9/00—Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
- E21D9/001—Improving soil or rock, e.g. by freezing; Injections
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/04—Lining with building materials
- E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
- E21D11/105—Transport or application of concrete specially adapted for the lining of tunnels or galleries ; Backfilling the space between main building element and the surrounding rock, e.g. with concrete
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
- E21D11/14—Lining predominantly with metal
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Abstract
The invention discloses a construction method of a shallow tunnel in a loess gully, which comprises the following steps: firstly, sleeve valve pipe grouting advanced reinforcement: grouting and reinforcing a sleeve valve pipe in a stratum of a construction area where the constructed shallow tunnel is located; secondly, excavating a tunnel and performing primary support; and thirdly, constructing a second lining. The method has simple steps, reasonable design, simple and convenient construction and good use effect, adopts the sleeve valve pipes to carry out grouting reinforcement on the reinforced stratum through the multiple rows of grouting holes, and specifically limits the range of the reinforced stratum, thereby not only reinforcing the tunnel body of the tunnel, but also reinforcing the tunnel base, having reliable reinforcement effect, being particularly suitable for advanced reinforcement and excavation construction of a shallow tunnel section which is positioned in a loess gully and has a silted soil stratum on the earth surface and is adjacent to a soil-stone interface, effectively ensuring the safety and reliability of the excavation process of the shallow tunnel in the loess gully, effectively improving the stability of the excavated molded tunnel and simultaneously effectively improving the bearing capacity of the tunnel base.
Description
Technical Field
The invention belongs to the technical field of tunnel construction, and particularly relates to a construction method of a shallow tunnel in a loess gully.
Background
The valley is a groove-shaped depression formed by violent erosion, and the small valley is only ten meters long and the large valley can reach dozens of kilometers. The storm flows are mostly formed by the convergence of the sheet flow of the sloping fields, and the surface of the sloping fields is not flat, so that locally low and flat concave lands exist. In the concave place, the flow particles of its two sides and upstream sheet are converged toward the lowest position in the middle to form flow core line, and under the condition of that said water layer is thickened, its flow rate is increased and its flushing capacity is raised, the concave place is gradually flushed and deepened to form valley and valley running water. According to the size and development form of the valley, there are four main types: namely, narrow furrow, incised furrow, gully and depressed furrow (dry valley). Among them, the gully usually develops on a bare slope, the water flow flows along the slope and often gathers into a plurality of streams, and after erosion, a generally parallel narrow gully is formed, and the narrow gully is continuously eroded and enlarged to develop into a gully (the width is about 1 m-2 m, and the cross section is V-shaped). The gully is formed by further development of a gully, and under the action of water flow tracing erosion, the gully head continuously retreats to generate a steep ridge and drop water; because of erosion, the groove is widened, the cross section is in a V shape, the length reaches thousands of meters to tens of kilometers, and the depth is thousands of meters to tens of meters. The gully is a groove formed by scouring the ground surface by discontinuous running water, the gully is the largest scale in the erosion gully, the length can reach thousands of meters or tens of kilometers, the depth can reach tens of meters or tens of meters, and sometimes can reach more than one hundred meters.
Loess refers to yellow silt deposit which is carried by wind during the quaternary period in geological times. The loess collapsibility coefficient (also called collapsibility coefficient) is a mechanical parameter for evaluating collapsibility of loess, and refers to the ratio of the height difference of a soil sample before and after soaking to the original height of the soil sample under a certain pressure. The loess collapsibility coefficient is an important index for evaluating the collapsibility of loess, and can be directly measured by experiments. Loess is classified into collapsible loess and non-collapsible loess according to the difference in the coefficient of collapse of loess. Wherein the non-collapsible loess is loess which is completely not collapsed or has a loess collapse coefficient of less than 0.015 after being wetted by water under the action of self weight and external load. Non-collapsible loess is extra soil formed under arid climatic conditions, generally light yellow, grayish yellow or yellowish brown, having large pores and vertical joints visible to the eye. The collapsible loess refers to soil which has obvious additional deformation caused by structural damage of soil after being soaked under the action of self-weight stress of an upper soil layer or under the combined action of the self-weight stress and the additional stress, belongs to special soil, has collapsible property even if being filled with miscellaneous materials, and is widely distributed in northeast, northwest, China and east China of China.
The loess valley is a valley developed in loess areas and can be divided into a valley bottom, a valley head and a valley slope. The formation and development of loess valleys are mainly a result of the erosion of the valley running water and the movement of loess materials of the slope. The loess area has developed gully, and the ground is cut to be separated and broken, so as to form a landscape with thousands of gullies. The valleys of the loess plateau in china are generally classified into three types, i.e., small furrows (e.g., fine furrows, shallow furrows, cut furrows) between furrows, valleys (e.g., gullies, dry furrows) between furrows and ground, and river furrows. Loess gully is formed by temporary linear water flow erosion action on loess accumulation, is characterized by deep furrow, steep wall and obvious erosion action to source, and mainly develops in the area with thick loess coverage and rare vegetation. The loess gully has the following characteristics: first, the gully is narrow and deep, the depth is usually from several meters to tens of meters, some reaches tens of meters, the length is from hundreds of meters to thousands of meters; secondly, the shape of the ditch head is mostly wedge-shaped, tunnel-shaped or palm-shaped; thirdly, the gullies are distributed in a tree shape or a grid shape and the like and are developed by fine furrows; and fourthly, in rainy seasons, sluiceways often collapse, slide, collapse, slide and slide, and the like, so that the damage to farmlands, roads and buildings is serious.
The loess stratum has geological characteristics such as porosity, vertical joint development, strong water permeability and settleability, easily produces the condition such as face collapse and primary support structure large deformation in tunnel engineering construction, when especially constructing to being located the shallow loess tunnel that buries in the loess gully, the excavation degree of difficulty is bigger. In the loess valley development process, except for flowing water scouring, water dropping, vortex, gravity collapse and the like play important roles. Geological survey shows that the lower part of the earth surface in the loess gully is generally silted soil with large water content, and the deeper the gully, the thicker the silted soil below the earth surface, and the more ten meters the lower part of the earth surface in the loess gully can be silted soil. The silted soil is formed by piling up in still water or slow flowing water, the soil body in the silted soil layer is silted soil, the water content of the soil body is large (the water content is generally more than 20%), vertical cracks develop, and the vault is chipped and is in a massive discrete body structure after tunnel excavation, so that the situations of tunnel face collapse, large deformation of a primary supporting structure and the like are easily caused, the construction risk is high, and the construction difficulty is large.
In addition, due to the special mechanical characteristics and structural characteristics of loess, poor stability and low bearing capacity of surrounding rocks are main problems faced by loess tunnel construction. The loess tunnel in the operation period, especially the heavy haul railway tunnel, the basement is very easy to generate the settlement deformation under the long-term train vibration load effect, and the driving condition is deteriorated and the driving safety is endangered in serious cases. Therefore, according to the engineering characteristics of the loess, a reasonable, feasible and effective durable substrate reinforcement treatment technology is adopted, and the improvement of the bearing capacity of the substrate is an urgent engineering problem to be solved in the construction of the heavy-duty loess railway tunnel. When the loess tunnel is under construction, need effectively to improve tunnel basement bearing capacity to effectively solve loess tunnel basis weak, subside the big scheduling problem of deformation.
Disclosure of Invention
The invention aims to solve the technical problems in the prior art, and provides a construction method of a shallow tunnel in a loess gully, which has the advantages of simple steps, reasonable design, simple and convenient construction and good use effect.
In order to solve the technical problems, the invention adopts the technical scheme that: a construction method of a shallow tunnel in a loess gully is characterized by comprising the following steps:
step one, grouting a sleeve valve pipe and reinforcing in advance: grouting and reinforcing a sleeve valve pipe in a stratum of a construction area where the constructed shallow tunnel is located;
the constructed shallow tunnel is a shallow tunnel which is positioned in the loess gully and penetrates through the loess stratum, the stratum of the construction area where the constructed shallow tunnel is located is a reinforced stratum, the constructed shallow tunnel is a linear tunnel, and the constructed shallow tunnel and the reinforced stratum are horizontally arranged; the loess stratum is positioned above the rock stratum, and an interface between the loess stratum and the rock stratum is a soil-rock interface;
the reinforced stratum is arranged along the longitudinal extension direction of the tunnel of the constructed shallow tunnel, the longitudinal length of the reinforced stratum is the same as that of the constructed shallow tunnel, and the width of the reinforced stratum is larger than the excavation width of the constructed shallow tunnel; the loess stratum comprises a silted soil stratum and a non-collapsible loess stratum which is positioned below the silted soil stratum, the constructed shallow tunnel is positioned in the non-collapsible loess stratum, and the silted soil stratum is positioned above the constructed shallow tunnel; the non-collapsible loess stratum is positioned above the soil-stone interface, and the distance between the bottom of the constructed shallow tunnel and the soil-stone interface is not more than 6 m; the cross section of the reinforced stratum is rectangular, the upper surface of the reinforced stratum is higher than the vault of the constructed shallow tunnel, and the bottom surface of the reinforced stratum is positioned below the earth-rock interface; the reinforced stratum is internally provided with a plurality of rows of grouting holes for grouting sleeve valve pipes, the plurality of rows of grouting holes are arranged from back to front along the longitudinal extension direction of the tunnel, each row of grouting holes comprises a plurality of grouting holes which are vertically arranged and are positioned on the cross section of the same tunnel, and the grouting holes in the front and back adjacent rows of grouting holes are arranged in a staggered manner; all grouting holes in the reinforced stratum are distributed in a quincunx shape and are uniformly distributed, and the distance between every two adjacent grouting holes in the reinforced stratum is 1.8-2.2 m; the grouting holes are cylindrical drill holes which are vertically distributed and are drilled into the rock stratum from the ground surface from top to bottom, and the hole bottom of each grouting hole is flush with the bottom surface of the stratum to be reinforced;
when sleeve valve pipe grouting reinforcement is carried out on a reinforced stratum, the method comprises the following steps:
step F1, drilling and sleeve valve pipe installation: drilling each grouting hole in a plurality of rows of grouting holes in the stratum to be reinforced, installing a sleeve valve pipe in each formed grouting hole, and enabling the bottom of the installed sleeve valve pipe to extend into the bottom of the installed grouting hole;
after the multiple rows of grouting holes in the reinforced stratum are drilled and the sleeve valve pipes are installed in each grouting hole, obtaining the multiple rows of sleeve valve pipes which are installed in place;
step F2, grouting sleeve valve tubes: performing sleeve valve pipe grouting reinforcement on the reinforced stratum through the plurality of rows of sleeve valve pipes in the step F1 to finish the sleeve valve pipe grouting reinforcement process of the reinforced stratum;
step two, tunnel excavation and primary support: excavating the constructed shallow tunnel from back to front along the longitudinal extension direction of the tunnel, and synchronously performing primary support on the tunnel hole formed by excavation from back to front in the excavation process to obtain a primary support structure of the tunnel formed by construction;
step three, second lining construction: and in the second step, in the process of carrying out primary support on the excavated tunnel hole from back to front, constructing a secondary lining of the tunnel on the inner side of the constructed primary support structure of the tunnel from back to front along the longitudinal extension direction of the tunnel.
The construction method of the shallow tunnel in the loess gully is characterized by comprising the following steps: the tunnel buried depth of the shallow tunnel constructed in the first step is 15-25 m; and the vertical distance between the upper surface of the reinforced stratum and the vault of the constructed shallow tunnel is H, and the value range of H is 4-6 m.
The construction method of the shallow tunnel in the loess gully is characterized by comprising the following steps: and in the step one, the left side wall and the right side wall of the reinforced stratum are symmetrically arranged on the left side and the right side of the constructed shallow tunnel, and the width of the reinforced stratum is 5-8 m larger than the excavation width of the constructed shallow tunnel.
The construction method of the shallow tunnel in the loess gully is characterized by comprising the following steps: the height of the hole section at the bottom of the grouting hole in the rock stratum is not less than 0.5m, and the aperture of the grouting hole is phi 100 mm-phi 120 mm.
The construction method of the shallow tunnel in the loess gully is characterized by comprising the following steps: all grouting holes in the stratum to be reinforced are distributed in multiple rows, and each row of grouting holes comprises a plurality of grouting holes which are distributed on the same vertical surface from back to front along the longitudinal extension direction of the tunnel; a row of grouting holes are distributed on the center line of the constructed shallow tunnel;
after the sleeve valve pipe grouting reinforcement process of the reinforced stratum is completed in the step F2, the sleeve valve pipe grouting reinforcement effect of the reinforced stratum needs to be checked by adopting a drilling and coring method;
when the sleeve valve pipe grouting reinforcement effect of the reinforced stratum is checked by adopting a drilling coring method, drilling inspection holes in the reinforced stratum from top to bottom by adopting a drilling coring drilling machine and obtaining drill cores in the inspection holes;
the method comprises the following steps that (1) an inspection hole drilled in a reinforced stratum is an internal inspection hole, and the internal inspection hole is a grouting inspection hole; the grouting inspection holes are cylindrical drill holes which are vertically arranged and are drilled into the rock stratum from the ground surface from top to bottom, and the hole bottoms of the grouting inspection holes are positioned below the bottom surface of the reinforced stratum;
the number of the internal inspection holes is multiple, the internal inspection holes are divided into three inspection hole groups from left to right, and each inspection hole group is positioned between two adjacent rows of grouting holes on the left and right; each inspection hole group comprises a plurality of internal inspection holes which are arranged on the same vertical surface from back to front along the longitudinal extension direction of the tunnel; the three inspection hole groups are respectively a middle inspection hole group, a left side inspection hole group positioned on the left side of the middle inspection hole group and a right side inspection hole group positioned on the right side of the middle inspection hole group, the left side inspection hole group and the right side inspection hole group are symmetrically distributed on the left side and the right side of the middle inspection hole group, and the middle inspection hole group is positioned on the left side or the right side of a tunnel center line of the constructed shallow tunnel; the inner inspection holes in the middle inspection hole group and the inner inspection holes in the left inspection hole group are arranged in a staggered manner; the left side inspection hole group and the right side inspection hole group are both located on the outer side of the excavation contour line of the constructed shallow tunnel.
The construction method of the shallow tunnel in the loess gully is characterized by comprising the following steps: when the grouting reinforcement effect of the sleeve valve pipe of the reinforced stratum is checked by adopting a drilling coring method, an external inspection hole is drilled outside the reinforced stratum from top to bottom by adopting a drilling coring drilling machine, and the external inspection hole is positioned on the left side or the right side of the reinforced stratum; the external inspection hole is the grouting inspection hole.
The construction method of the shallow tunnel in the loess gully is characterized by comprising the following steps: in the first step, the cross section of the tunnel where each row of grouting holes are located is a grouting reinforcement surface of a reinforced stratum, the row of grouting holes located on the rearmost side in the reinforced stratum are rear end grouting holes, and the grouting reinforcement surface where the rear end grouting holes are located is a rear end reinforcement surface; each row of the grouting holes comprises a plurality of first-stage grouting holes and a plurality of second-stage grouting holes, and the first-stage grouting holes and the second-stage grouting holes are arranged in a staggered mode;
when grouting sleeve valve pipes is performed in the step F2, grouting reinforcement is performed on the reinforced stratum through the plurality of rows of sleeve valve pipes from back to front along the longitudinal extension direction of the tunnel, and the grouting reinforcement methods of the plurality of rows of sleeve valve pipes are the same;
when grouting reinforcement is carried out on the reinforced stratum through any row of sleeve valve pipes, the sleeve valve pipes are used for grouting reinforcement on the reinforced stratum through the row of sleeve valve pipes for multiple times from first to last, and the grouting reinforcement surface where the row of sleeve valve pipes is located is the current reinforcement surface; when grouting reinforcement is carried out through the sleeve valve pipe, the process is as follows:
step F21, grouting and reinforcing the sleeve valve pipe for the first time: the sleeve valve pipe is arranged to carry out primary grouting reinforcement on the reinforced stratum, and the method comprises the following steps:
step F211, grouting and reinforcing the grouting holes in the first stage: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes, which are positioned in each stage of grouting hole, and the grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
step F212, grouting and reinforcing the second-stage grouting holes: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes in each secondary grouting hole in the step F211, and grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
grouting reinforcement is carried out by adopting a sectional grouting method when grouting reinforcement is carried out through the sleeve valve pipes in any one of the first-stage grouting holes in the step F211 and grouting reinforcement is carried out through the sleeve valve pipes in any one of the second-stage grouting holes in the step F212, the grouting sectional step distance is 50-100 cm, and the grouting speed is 10-100L/min;
in addition, in the step F211 and the step F212, during grouting through the sleeve valve pipe in any grouting hole, synchronously observing the grouting pressure and the grouting speed of the sleeve valve pipe in the grouting hole, stopping grouting when the grouting pressure reaches F0 and is kept unchanged for more than 10min or the grouting speed is reduced to be less than 5L/min, completing the grouting reinforcement process of the sleeve valve pipe in one grouting hole, and recording the grouting reinforcement termination condition of the grouting hole during the current grouting reinforcement; wherein F0 is a pre-designed grouting final pressure value, and the value range of F0 is 4 MPa-6 MPa;
the grouting reinforcement termination conditions of each grouting hole are that the grouting pressure reaches the standard or the grouting amount reaches the standard;
when the grouting reinforcement termination condition of any one grouting hole is determined, when the sleeve valve pipe in the grouting hole stops grouting, the grouting pressure of the sleeve valve pipe reaches a design final pressure value F0 and is kept unchanged for more than 10min, and the grouting reinforcement termination condition of the grouting hole is judged to be that the grouting pressure reaches the standard; when the sleeve valve pipe in the grouting hole stops grouting, the grouting speed of the sleeve valve pipe is reduced to be below 5L/min, and the grouting reinforcement termination condition of the grouting hole is judged to be that the grouting amount reaches the standard;
step F213, grouting and reinforcing the sleeve valve pipe to finish judgment: judging grouting reinforcement termination conditions of all grouting holes in the reinforced stratum during the current grouting reinforcement recorded in the step F211 and the step F212: when the grouting reinforcement termination conditions of all grouting holes in the reinforced stratum during the current grouting reinforcement recorded in step F211 and step F212 are that the grouting pressure reaches the standard, determining that the grouting reinforcement process of the sleeve valve pipe of the current reinforcement surface is completed, and entering step F24; otherwise, go to step F22;
step F22, grouting and reinforcing the sleeve valve pipe for the next time: the next grouting reinforcement is carried out on the reinforced stratum through the sleeve valve pipe, and the method comprises the following steps:
step F221, grouting and reinforcing the grouting holes in the first stage: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes, which are positioned in each stage of grouting hole, and the grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
step F222, grouting and reinforcing the second-stage grouting holes: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes in each secondary grouting hole in the step F221, and grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
grouting reinforcement is carried out by adopting a sectional grouting method when grouting reinforcement is carried out through the sleeve valve pipe in any one of the first-stage grouting holes in the step F221 and grouting reinforcement is carried out through the sleeve valve pipe in any one of the second-stage grouting holes in the step F222, the grouting sectional step distance is 50 cm-100 cm, and the grouting speed is 10L/min-100L/min;
in addition, in the step F221 and the step F222, during grouting through the sleeve valve pipe in any grouting hole, synchronously observing the grouting pressure and the grouting speed of the sleeve valve pipe in the grouting hole, stopping grouting when the grouting pressure reaches a design final pressure value F0 and is kept unchanged for more than 10min or the grouting speed is reduced to be less than 5L/min, completing the grouting reinforcement process of the sleeve valve pipe in one grouting hole, and recording the grouting reinforcement termination condition of the grouting hole during the current grouting reinforcement;
step F223, grouting and reinforcing the sleeve valve pipe to finish judgment: judging grouting reinforcement termination conditions of all grouting holes in the reinforced stratum during the grouting reinforcement of the current time recorded in the step F221 and the step F222: when the grouting reinforcement termination conditions of all grouting holes in the reinforced stratum during the current grouting reinforcement recorded in the step F221 and the step F222 are that the grouting pressure reaches the standard, judging that the grouting reinforcement process of the sleeve valve pipe of the current reinforcement surface is completed, and entering the step F24; otherwise, go to step F23;
step F23, returning to the step F22, and carrying out next grouting reinforcement on the reinforced stratum through the row of sleeve valve pipes;
step F24, grouting and reinforcing the next row of sleeve valve pipes: grouting and reinforcing the reinforced stratum through the sleeve valve pipes in the next row according to the method from the step F21 to the step F23;
step F25, grouting and reinforcing the reinforced stratum and judging: judging whether the sleeve valve pipe grouting reinforcement process of the rear end reinforcement surface in the reinforced stratum is finished or not, judging that the sleeve valve pipe grouting reinforcement process of the reinforced stratum is finished when the sleeve valve pipe grouting reinforcement process of the rear end reinforcement surface in the reinforced stratum is finished through judgment, and entering the step two; otherwise, return to step F24.
The construction method of the shallow tunnel in the loess gully is characterized by comprising the following steps: before sleeve valve pipe grouting advanced reinforcement is carried out in the first step, spraying a layer of concrete on the tunnel face of the constructed shallow tunnel for sealing;
when tunnel excavation and primary support are carried out in the second step, in the process of sleeve valve pipe grouting advanced reinforcement in the first step, excavating the constructed shallow tunnel from back to front along the longitudinal extension direction of the tunnel, wherein the excavation surface of the constructed shallow tunnel is positioned behind the grouting reinforcement surface for currently carrying out sleeve valve pipe grouting reinforcement; and the distance between the excavation surface of the constructed shallow tunnel and the grouting reinforcement surface for grouting reinforcement of the sleeve valve pipe is larger than 15 m.
The construction method of the shallow tunnel in the loess gully is characterized by comprising the following steps: the tunnel supporting structure of the constructed shallow tunnel comprises a tunnel forepoling structure for forepoling the arch part of the tunnel hole, a tunnel primary supporting structure for preliminary supporting the tunnel hole and a tunnel secondary lining distributed on the inner side of the tunnel primary supporting structure, wherein the tunnel forepoling structure is positioned above the tunnel primary supporting structure, the tunnel primary supporting structure and the tunnel secondary lining are full-section supporting structures for carrying out full-section supporting on the tunnel hole, and the tunnel secondary lining is a reinforced concrete lining; the cross-sectional area of the tunnel hole is more than 100m2The tunnel hole is divided into an upper hole body, a middle hole body and a lower hole body from top to bottom; the upper portion hole body is formed after the upper step excavation is carried out on the constructed loess tunnel from back to front, the middle portion hole body is formed after the middle step excavation is carried out on the constructed loess tunnel from back to front, and the lower portion hole body is formed after the lower step excavation is carried out on the constructed loess tunnel from back to front;
the tunnel primary support structure comprises an arch wall primary support structure for primary support of an arch wall of a tunnel hole and a primary support inverted arch for primary support of the bottom of the tunnel hole, and the tunnel secondary lining comprises an arch wall secondary lining for supporting the arch wall of the tunnel hole and an inverted arch secondary lining for supporting the bottom of the tunnel hole; the inverted arch secondary lining is positioned above a primary supporting inverted arch, an inverted arch backfill layer is arranged on the inverted arch secondary lining, the upper surface of the inverted arch secondary lining is a horizontal plane, the bottoms of the left side and the right side of the arch wall secondary lining are horizontal planes, the arch wall secondary lining is supported on the inverted arch secondary lining and cast into a whole, and the inverted arch backfill layer is a concrete filling layer;
the tunnel primary support structure comprises a full-section support structure for performing full-section support on a tunnel hole, an arch wall net-jet support structure for performing primary support on an arch wall of the tunnel hole, an inverted arch primary support structure for performing primary support on the bottom of the tunnel hole and an anchoring system arranged on the outer side of the full-section support structure; the full-section supporting structure comprises a plurality of full-section supporting frames which are arranged from back to front along the longitudinal extension direction of the tunnel, the two adjacent full-section supporting frames at the front and the back are fixedly connected into a whole through a plurality of longitudinal connecting reinforcing steel bars, the longitudinal connecting reinforcing steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal connecting reinforcing steel bars are arranged along the contour line of the full-section supporting frames; the shape of the full-section support frame is the same as the shape of the cross section of the tunnel hole, each full-section support frame is formed by splicing an arch wall support arch frame for supporting an arch wall of the tunnel hole and a tunnel inverted arch support frame for supporting the bottom of the tunnel hole, the tunnel inverted arch support frame is positioned right below the arch wall support arch frame, the arch wall support arch frame and the tunnel inverted arch support frame are positioned on the same tunnel cross section, and the tunnel inverted arch support frame and the arch wall support arch frame form a closed full-section support frame;
the arch wall mesh-spraying supporting structure and the arch wall steel arch frame in the full-section supporting structure form an arch wall primary supporting structure, and the inverted arch primary supporting structure and the tunnel inverted arch support in the full-section supporting structure form a primary supporting inverted arch; the inverted arch primary support structure is an inverted arch concrete injection layer injected at the bottom of the tunnel, and the tunnel inverted arch support is fixed in the inverted arch concrete injection layer;
the arch wall supporting arch center consists of an upper arch center positioned in the upper tunnel body, two middle side brackets symmetrically distributed below the left side and the right side of the upper arch center and positioned in the middle tunnel body, and two lower side brackets symmetrically distributed below the left side and the right side of the upper arch center and positioned in the lower tunnel body, wherein the tunnel inverted arch bracket is positioned in the lower tunnel body; each middle side support is connected between the upper end of one lower side support and the upper arch frame; the left end of the tunnel inverted arch support is fixedly connected with the bottom of one lower side support, and the right end of the tunnel inverted arch support is fixedly connected with the bottom of the other lower side support;
the anchoring system comprises a plurality of anchoring groups which are arranged from back to front along the longitudinal extension direction of the tunnel, one anchoring group is uniformly distributed on the outer side of each full-section supporting frame, and each full-section supporting frame and the anchoring group arranged on the full-section supporting frame are arranged on the same cross section of the tunnel;
each anchoring group comprises a left group of upper locking leg anchor pipes, a right group of middle locking leg anchor pipes and a left group of lower locking leg anchor pipes, wherein the left group of upper locking leg anchor pipes and the right group of middle locking leg anchor pipes are symmetrically arranged at the outer sides of the bottoms of the left side and the right side of the upper arch frame; a group of middle locking leg anchor pipes is arranged on the outer side of the bottom of each middle side support, and a group of lower locking leg anchor pipes is arranged on the outer side of the bottom of each lower side support; each group of upper lock leg anchor pipes comprises an upper lock leg anchor pipe and a lower lock leg anchor pipe which are arranged in parallel, each group of middle lock leg anchor pipes comprises an upper middle lock leg anchor pipe and a lower middle lock leg anchor pipe which are arranged in parallel, and each group of lower lock leg anchor pipes comprises an upper lower lock leg anchor pipe and a lower lock leg anchor pipe which are arranged in parallel; the upper lock leg anchor pipe, the middle lock leg anchor pipe and the lower lock leg anchor pipe are all lock leg anchor pipes which enter soil layers on the periphery of the tunnel from inside to outside and are gradually inclined downwards from inside to outside;
when the second lining construction is carried out in the third step, when the tunnel secondary lining is constructed from back to front, the inverted arch secondary lining is constructed on the constructed primary support inverted arch from back to front, and the inverted arch secondary lining formed by construction is obtained; in the process of constructing the secondary lining of the inverted arch from back to front, constructing the secondary lining of the arch wall on the constructed secondary lining of the inverted arch from back to front, and connecting the constructed secondary lining of the arch wall and the secondary lining of the inverted arch positioned below the constructed secondary lining of the inverted arch into a whole to obtain the constructed secondary lining of the tunnel;
in the step, in the construction process of the inverted arch secondary lining from back to front, after concrete poured in the inverted arch secondary lining is finally solidified, the inverted arch secondary lining and a primary support inverted arch form the tunnel inverted arch structure formed by construction.
The construction method of the shallow tunnel in the loess gully is characterized by comprising the following steps: and step two, when tunnel excavation and primary support are carried out, the method comprises the following steps:
step B1, excavating an upper cavity and performing primary support: excavating an upper cavity of the constructed loess tunnel from back to front along the longitudinal extension direction of the tunnel;
in the process of excavating the upper cavity, carrying out net-spraying support on the arch part of the upper cavity formed by excavation from back to front, and simultaneously installing an upper arch frame in the upper cavity formed by excavation from back to front so as to finish the excavation and primary support construction process of the upper cavity;
step B2, excavating a middle cavity and performing primary support: b1, excavating the middle cavity below the excavated and molded upper cavity from back to front along the longitudinal extension direction of the tunnel in the process of excavating the upper cavity and primary supporting;
in the middle hole body excavation process, respectively carrying out net-spraying support on the left side and the right side of the excavated and molded middle hole body from back to front, and simultaneously respectively installing middle side supports on the left side and the right side of the excavated and molded middle hole body from back to front, and firmly connecting each middle side support with the upper arch frame in the step B1 into a whole, so that the excavation and primary support construction process of the middle hole body is completed;
in the step, the excavation surface of the middle cavity body is positioned behind the excavation surface of the upper cavity body, and the horizontal distance between the excavation surface of the middle cavity body and the excavation surface of the upper cavity body is 4-6 m;
step B3, excavating a lower cavity and performing primary support: b2, excavating the lower cavity below the excavated and formed middle cavity from back to front along the longitudinal extension direction of the tunnel in the process of excavating the middle cavity and primary supporting;
in the lower hole excavation process, respectively carrying out net-spraying support on the left side and the right side of the excavated and molded lower hole from back to front, synchronously respectively installing lower side supports on the left side and the right side of the excavated and molded lower hole from back to front in the net-spraying support process, and fixedly connecting each lower side support with the middle side support in the step B2 into a whole; meanwhile, a tunnel inverted arch support is arranged at the bottom of the lower hole body from back to front, and the arranged tunnel inverted arch support is fixedly connected with lower side supports arranged at the left side and the right side of the lower hole body into a whole; in the installation process of the tunnel inverted arch support, synchronously spraying a layer of concrete at the bottom of the tunnel from back to front to form an inverted arch concrete spraying layer, fixing the tunnel inverted arch support in the inverted arch concrete spraying layer, and completing the excavation of a lower part of a tunnel body and the primary support construction process;
in the step, the excavation surface of the lower cavity body is positioned behind the excavation surface of the middle cavity body, and the horizontal distance between the excavation surface of the lower cavity body and the excavation surface of the middle cavity body is 4-6 m;
in the step, in the process of excavating the lower hole body from back to front, an excavated tunnel is obtained; respectively carrying out net-spraying support on the left side and the right side of the excavated and molded lower hole body from back to front to obtain the constructed and molded arch wall net-spraying support structure; the arch wall mesh spraying support structure is connected with the inverted arch concrete spraying layer.
Compared with the prior art, the invention has the following advantages:
1. the method has the advantages of simple steps, reasonable design, simple and convenient construction and lower input construction cost.
2. The position and the range of the reinforced stratum are reasonable in design, the reinforced stratum is reinforced through grouting, the safety and the reliability of the tunnel excavation process can be ensured, and the stability of the excavated molded tunnel can be effectively improved.
3. The grouting inspection holes are formed in the reinforced stratum, the grouting inspection holes are reasonably arranged, the grouting effect of each position of the reinforced stratum after grouting reinforcement can be effectively checked, and the grouting reinforcement effect of the sleeve valve pipe is ensured.
4. The sleeve valve pipe grouting reinforcement effect is good, the sleeve valve pipe is adopted, and grouting reinforcement is carried out on a reinforced stratum through a plurality of rows of grouting holes, so that the tunnel body of the tunnel hole can be reinforced, the tunnel base can also be reinforced, the reinforcement effect is reliable, the sleeve valve pipe grouting reinforcement method is particularly suitable for advanced reinforcement of a shallow tunnel section which is located below the ground in loess valley and is filled with the silted soil, the silted soil stratum can be simply, conveniently, quickly and effectively reinforced, the safety and reliability of the tunnel excavation process are ensured, the stability of the excavated tunnel hole can be effectively improved, the tunnel face is prevented from collapsing in the tunnel excavation process, and the primary support structure can be effectively controlled from large deformation; compared with full-section curtain grouting reinforcement, the construction efficiency can be greatly improved, the construction period is shortened, and the construction cost is reduced. And when the sleeve valve pipe is adopted for grouting for reinforcement, the grouting can be segmented, quantified and intermittent, the grouting range and the grouting pressure can be well controlled, repeated grouting can be performed, the possibility of slurry overflow and slurry mixing is low, and the grouting reinforcement effect is easy to guarantee.
5. The tunnel supporting structure that adopts reasonable in design, the construction is simple and convenient and the input cost is lower, will carry out advance support's tunnel advance support structure to the tunnel cave hunch portion of loess tunnel under construction and carry out the tunnel primary support structure and the tunnel secondary lining that full section was strutted to the tunnel cave and constitute the combined supporting system, stabilize, reliably strut big section loess tunnel.
6. The full-section support frame can support the tunnel hole in a full-section manner, the support is stable and reliable, the full-section support frame is formed by assembling an arch wall support arch frame and a tunnel inverted arch frame, the arch wall support arch frame is formed by assembling an upper arch frame, two middle side supports and two lower side supports, the assembly can be simply and conveniently carried out when the tunnel is actually excavated, the requirement of supporting the section of the tunnel hole in blocks is met, the primary support of the upper hole body is not influenced by the primary support construction in the middle hole body and the lower hole body, the primary support of the middle hole body is not influenced by the primary support construction in the lower hole body, the primary support of the upper hole body and the primary support of the middle hole body are constructed immediately after the excavation is finished, so that the support is timely and stable, the tunnel hole is not completely excavated at the moment, and the support stability of the primary support structure in the upper hole body and the middle hole body of the tunnel is further ensured, and the preliminary bracing process in tunnel upper portion cavern body and the middle part cavern body is changeed in going on, and it is more powerful to strut simultaneously, more is favorable to tunnel construction safety.
7. And the anchoring system is adopted to fix the surrounding rock of the tunnel in a full section manner, so that the primary support stability is further improved. And moreover, the anchoring system and the full-section support frame are connected into a whole, the overall stability is further improved, and meanwhile, the construction is simple and convenient.
8. Advance support adopts advance little pipe slip casting supporting construction, and the construction is simple and convenient and the efficiency of construction is high, can effectively ensure the advance support intensity and the effect of strutting in big section loess tunnel, can carry out effective restriction to loess tunnel hunch portion deformation.
9. The upper surface of the secondary lining inverted arch is adjusted to be a horizontal plane, the interface between the inverted arch secondary lining and the inverted arch filling layer is adjusted to be the horizontal plane, the construction is simple and convenient, the construction efficiency is high, the inverted arch filling layer and the inverted arch secondary lining can be poured simultaneously, the construction process of the inverted arch secondary lining and the inverted arch filling layer can be greatly simplified, the concrete of the inverted arch secondary lining and the inverted arch filling layer cannot be mixed into a whole, the construction quality of the inverted arch secondary lining and the inverted arch filling layer can be effectively ensured, and the problems that the construction quality of the inverted arch secondary lining and the inverted arch filling layer cannot be ensured and the like due to different concrete grades are avoided. Meanwhile, the upper surface of the inverted arch secondary lining is a horizontal plane, the arc shape of the inverted arch secondary lining is not required to be guaranteed in the concrete pouring process, an arc-shaped template is not required to be adopted, the pouring is convenient to carry out by a large margin, the pouring is simple and convenient, and the construction quality of the inverted arch secondary lining is easy to guarantee.
10. The tunnel secondary lining is reasonable in structure, the tunnel secondary lining is formed by connecting an inverted arch secondary lining and an arch wall secondary lining, and the middle arc part inside the inverted arch secondary lining is optimized to be a horizontal plane. The inverted arch secondary lining after optimizing makes tunnel inverted arch structure's rigidity whole promote by a wide margin to need not to install the arc template in the construction, concrete vibration is simple and convenient and the quality of vibrating is easily controlled, and inverted arch secondary lining's external dimension and construction quality change in the control, and can improve tunnel inverted arch's efficiency of construction by a wide margin, tunnel secondary lining's seal time shortens greatly to do not have the interference of arc template to make inverted arch concrete easily vibrate, concrete quality promotes greatly. Simultaneously, will have two lining arch wall liners now and two low side walls to be connected and constitute whole lining (promptly arch wall secondary lining) and construct to adopt two lining dollies to construct to arch wall secondary lining, once construction shaping can further improve tunnel secondary lining's efficiency of construction, accelerate tunnel secondary lining seal time shortens tunnel secondary lining's seal ring time further improves the structural stability in loess tunnel of being under construction, can effectively reduce simultaneously construction joint among the tunnel secondary lining makes tunnel secondary lining's wholeness stronger, and whole atress effect is better.
11. The adopted advanced small conduit grouting supporting structure is reasonable in design, simple and convenient to construct and good in using effect, effectively reinforces the arch part of the tunnel and forms a stable arch wall bearing ring, can effectively improve the self-stabilizing capacity of rock strata on the periphery of a tunnel body, can effectively save construction cost and save construction period, and meanwhile, construction equipment is simple, and the preliminary bracing construction is timely carried out after the tunnel entering construction, and the working procedures are closely linked. Moreover, the disturbance to the soil layers on the peripheral sides in the supporting process is small, the construction cost is low, the problems that the arch part of the tunnel is easy to deform and settle under the influence of horizontal pressure generated after the tunnel is excavated can be effectively solved, and the arch part of the tunnel can be stably supported.
12. The sleeve valve pipe advanced grouting reinforcement method is simple, reasonable in design and simple and convenient to construct, can reinforce the tunnel body of the tunnel and the tunnel base, is reliable in reinforcement effect, and is particularly suitable for advanced reinforcement of a shallow tunnel section which is located below the ground in loess valley and is provided with silted soil and is adjacent to a soil-stone interface; meanwhile, the adopted tunnel excavation and supporting method has simple steps, reasonable design, simple and convenient construction and good use effect, adopts a three-step excavation mode and limits the intervals among the excavation surface of the middle part of the tunnel body, the excavation surface of the upper part of the tunnel body and the excavation surface of the lower part of the tunnel body, realizes the short-step or micro-step excavation of the large-section tunnel and ensures the stability of the excavated molded tunnel; in addition, the full-section support frame structure tunnel is adopted for layered supporting, and an anchoring system is adopted for integrally reinforcing the outer side of the tunnel, so that the structural stability of the large-section loess tunnel is ensured, and the construction safety is ensured; meanwhile, a tunnel bottom backfill soil layer on the rear side of the excavation surface of the lower hole body serves as a temporary moving platform for the wet spraying manipulator to move back and forth, the excavation height of the upper hole body and the middle hole body is limited, the purpose of concrete spraying through the wet spraying manipulator in the excavation process is achieved, the construction progress can be effectively accelerated, the primary support can be enabled to be quickly sealed into a ring, the stability of the tunnel structure is further ensured, the construction is simple, the construction speed is high, and the construction process is safe and reliable. Meanwhile, the tunnel secondary lining structure is reasonable in design, the construction method is simple, and the construction quality is easy to control, so that the construction cost can be greatly reduced, the construction period can be saved, and the construction safety can be ensured. According to the support method, the support method has the characteristics of safety, reliability, high degree of mechanization, high construction speed, low labor intensity, advanced construction period, cost saving and the like through a three-step construction method, and the lower step and the primary support of the inverted arch are constructed simultaneously according to the geological characteristics of the loess tunnel, so that the lower step and the primary support of the inverted arch can be closed to form a ring in time in the shortest time, the overlarge deformation of surrounding rocks is prevented, and the construction safety is ensured; in addition, the construction method is simplified, the interference among all the procedures is prevented, the mechanized construction can be met to the maximum extent, the labor intensity is reduced, the space full-section flow construction is adopted, the construction efficiency can be improved, and the engineering cost is reduced. In addition, the temporary inverted arch is cancelled, so that the engineering cost is reduced, and the safety risk in the process of dismantling the temporary inverted arch is avoided. Therefore, the construction process of the shallow tunnel in the loess valley can be simply, conveniently and quickly finished, and the construction process is safe and reliable.
In conclusion, the method has the advantages of simple steps, reasonable design, simplicity and convenience in construction and good use effect, the sleeve valve pipes are adopted, the reinforced stratum is subjected to grouting reinforcement through the multiple rows of grouting holes, the range of the reinforced stratum is specifically limited, the tunnel body and the tunnel base of the tunnel can be reinforced, the reinforcement effect is reliable, the method is particularly suitable for advanced reinforcement and excavation construction of the shallow tunnel section which is located in the loess gully and has a silted soil stratum on the earth surface and is adjacent to a soil-stone interface, the safety and reliability of the excavation process of the shallow tunnel in the loess gully can be effectively ensured, and the stability of the excavated tunnel can be effectively improved. Meanwhile, the bearing capacity of the tunnel base can be effectively improved, and the problems that the shallow-buried loess tunnel foundation is weak, the settlement deformation is large and the like are effectively solved.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a flow chart of the construction method of the present invention.
Fig. 2 is a flow chart of a method for grouting advanced reinforcement of a sleeve valve pipe according to the invention.
FIG. 3 is a schematic plan view of the placement of all grouting holes in the consolidated formation according to the present invention.
FIG. 4 is a schematic illustration of the vertical layout of the consolidated formation of the present invention.
FIG. 5 is a schematic plan view of the placement of grout holes and grout holes in the consolidated formation according to the present invention.
Fig. 6 is a schematic cross-sectional structure view of the tunnel supporting structure of the present invention.
Fig. 7 is a schematic longitudinal sectional view of the tunnel supporting structure of the present invention.
FIG. 8 is a schematic view of the construction state of the wet-jet robot of the present invention.
Fig. 9 is a schematic cross-sectional view of the lower part of the inner side of the tunnel according to the present invention.
Fig. 10 is a schematic structural view of a front mold plate according to the present invention.
Description of reference numerals:
1, tunnel boring; 1-upper cavity; 1-2-a middle hole body;
1-3-lower cavity; 2-tunnel inverted arch support; 2-1-upper arch centering;
5-middle side support; 6-lower side support; 7-backfilling a soil layer at the bottom of the tunnel;
8, locking a pin anchor pipe; 9-middle locking leg anchor tube; 10-lower lock pin anchor pipe;
12-preliminary bracing structure of arch wall; 13-primary support inverted arch; 14-secondary lining of arch walls;
15-secondary lining of an inverted arch; 16-an inverted arch backfill layer; 17-movable inverted arch trestle;
18-short side wall; 19-arch wall concrete spraying layer;
20-an inverted arch concrete spraying layer; 21-wet spraying mechanical arm; 22-grouting small guide pipe;
23-a ditch cable trough; 24-sideform; 25-front template;
26-internal inspection hole; 27-external inspection hole; 28-consolidated formation;
29-a loess stratum; 30-a rock formation; 31-grouting holes.
Detailed Description
As shown in fig. 1, the construction method of the shallow tunnel in the loess gully comprises the following steps:
step one, grouting a sleeve valve pipe and reinforcing in advance: grouting and reinforcing a sleeve valve pipe in a stratum of a construction area where the constructed shallow tunnel is located;
with reference to fig. 3 and 4, the constructed shallow tunnel is a shallow tunnel located in the loess gully and penetrating through the loess stratum 29, the stratum of the construction area where the constructed shallow tunnel is located is the reinforced stratum 28, and the constructed shallow tunnel is a linear tunnel and is horizontally arranged with the reinforced stratum 28; the loess formation 29 is positioned above the rock formation 30, and an interface between the loess formation 29 and the rock formation 30 is a soil-rock interface;
the reinforced stratum 28 is arranged along the longitudinal extension direction of the tunnel of the constructed shallow tunnel, the longitudinal length of the reinforced stratum 28 is the same as that of the constructed shallow tunnel, and the width of the reinforced stratum 28 is larger than the excavation width of the constructed shallow tunnel; the loess stratum 29 comprises a silted soil stratum and a non-collapsible loess stratum below the silted soil stratum, the constructed shallow tunnel is positioned in the non-collapsible loess stratum, and the silted soil stratum is positioned above the constructed shallow tunnel; the non-collapsible loess stratum is positioned above the soil-stone interface, and the distance between the bottom of the constructed shallow tunnel and the soil-stone interface is not more than 6 m; the cross section of the reinforced stratum 28 is rectangular, the upper surface of the reinforced stratum 28 is higher than the vault of the constructed shallow tunnel, and the bottom surface of the reinforced stratum 28 is positioned below the earth-rock interface; a plurality of rows of grouting holes 31 for grouting sleeve valve pipes are formed in the reinforced stratum 28, the plurality of rows of grouting holes 31 are arranged from back to front along the longitudinal extension direction of the tunnel, each row of grouting holes 31 comprises a plurality of grouting holes 31 which are vertically arranged and are positioned on the cross section of the same tunnel, and the grouting holes 31 in the front and back adjacent rows of grouting holes 31 are arranged in a staggered manner; all the grouting holes 31 in the reinforced stratum 28 are distributed in a quincunx shape and are uniformly distributed, and the distance between every two adjacent grouting holes 31 in the reinforced stratum 28 is 1.8-2.2 m; the grouting holes 31 are cylindrical drill holes which are vertically arranged and are drilled into the rock stratum 30 from the ground surface from top to bottom, and the bottom of each grouting hole 31 is flush with the bottom surface of the stratum 28 to be reinforced;
as shown in fig. 2, when sleeve valve pipe grouting reinforcement is performed on the reinforced stratum 28, the method comprises the following steps:
step F1, drilling and sleeve valve pipe installation: drilling each grouting hole 31 in a plurality of rows of grouting holes 31 in the stratum 28 to be reinforced, installing a sleeve valve pipe in each formed grouting hole 31, and enabling the bottom of the installed sleeve valve pipe to extend into the bottom of the installed grouting hole 31;
after the multiple rows of grouting holes 31 in the reinforced stratum 28 are drilled and the sleeve valve pipes are installed in each grouting hole 31, obtaining multiple rows of sleeve valve pipes which are installed in place;
step F2, grouting sleeve valve tubes: performing sleeve valve pipe grouting reinforcement on the reinforced stratum 28 through the plurality of rows of sleeve valve pipes in the step F1 to finish the sleeve valve pipe grouting reinforcement process of the reinforced stratum 28;
step two, tunnel excavation and primary support: excavating the constructed shallow tunnel from back to front along the longitudinal extension direction of the tunnel, and synchronously performing primary support on the tunnel hole 1 formed by excavation from back to front in the excavation process to obtain a primary support structure of the tunnel formed by construction;
step three, second lining construction: and in the second step, in the primary support process of the tunnel hole 1 formed by excavation from back to front, the secondary lining of the tunnel is constructed on the inner side of the constructed primary support structure of the tunnel from back to front along the longitudinal extension direction of the tunnel.
The bottom of the constructed shallow tunnel refers to the bottom of an excavation contour line of the constructed shallow tunnel, and the vault of the constructed shallow tunnel refers to the vault of the excavation contour line of the constructed shallow tunnel (namely the top of a tunnel excavation section of the constructed shallow tunnel). The tunnel buried depth of the constructed shallow tunnel is less than 30m, and the tunnel buried depth refers to the vertical distance from the top of the tunnel excavation section to the natural ground (namely the ground surface).
In this embodiment, the tunnel buried depth of the shallow tunnel constructed in the first step is 15m to 25m, and the length of the shallow tunnel constructed in the first step is 20m to 50 m.
As shown in fig. 3, the vertical distance between the upper surface of the reinforced stratum 28 and the vault of the constructed shallow tunnel is H, and the value range of H is 4m to 6 m. In this example, H is 5 m. During actual construction, the value of H can be correspondingly adjusted according to specific requirements.
During actual construction, the aperture of the grouting hole 31 is phi 100 mm-phi 120 mm. The height of the hole section of the bottom of the grouting hole 31 in the rock stratum 30 is not less than 0.5m, wherein the height of the hole section of the bottom of the grouting hole 31 in the rock stratum 30 is marked as H1. The height of the consolidated stratum 28 is denoted as H0, H0 is H + H2+ H1, wherein H2 is the excavation height of the constructed shallow tunnel.
In this embodiment, the diameter of the grouting hole 31 is 110 mm. In the actual construction process, the distance between two adjacent grouting holes 31 in the consolidated formation, the aperture of the grouting hole 31 and the height of the hole section of the bottom of the grouting hole 31 in the rock stratum 30 can be adjusted correspondingly according to specific requirements.
The tunnel excavation section of the constructed shallow tunnel is notLess than 100m2Therefore, the constructed shallow tunnel is not less than 100m2And it is a large cross-section tunnel. In this embodiment, the tunnel excavation section of the constructed shallow tunnel is 110m2～170m2。
The excavation width of the constructed shallow tunnel is marked as D1, the width of the reinforced stratum 28 is marked as D2, wherein D1 is less than D2, and the value range of D1 is 10-15 m.
In the step one, the left side wall and the right side wall of the reinforced stratum 28 are symmetrically arranged on the left side and the right side of the constructed shallow tunnel, and the width of the reinforced stratum 28 is 5-8 m larger than the excavation width of the constructed shallow tunnel. In this embodiment, the width of the consolidated ground layer 28 is 6m greater than the excavation width of the shallow tunnel to be constructed, so D2 is D1+6 m.
During actual construction, the width of the consolidated formation 28 (i.e., the value of D2) may be adjusted accordingly according to specific needs.
As shown in fig. 3, in this embodiment, all the grouting holes 31 in the consolidated formation 28 are arranged in multiple rows, and each row of the grouting holes 31 includes multiple grouting holes 31 arranged on the same vertical plane from back to front along the longitudinal extension direction of the tunnel; a row of the grouting holes 31 is arranged on the middle line of the constructed shallow tunnel.
The one column of the grouting holes 31 positioned at the leftmost side among the plurality of columns of the grouting holes 31 in the stratum 28 to be consolidated is a left end grouting hole, the one column of the grouting holes 31 positioned at the rightmost side among the plurality of columns of the grouting holes 31 in the stratum 28 to be consolidated is a right end grouting hole, the left end grouting hole abuts against the left side wall of the stratum 28 to be consolidated, and the right end grouting hole abuts against the right side wall of the stratum 28 to be consolidated.
As shown in fig. 3, left grouting holes in the consolidated formation 28 are located on the left side of the constructed shallow tunnel, and right grouting holes in the consolidated formation 28 are located on the right side of the constructed shallow tunnel; all the left-side grouting holes in the consolidated formation 28 are arranged in left and right two rows, and all the right-side grouting holes in the consolidated formation 28 are arranged in left and right two rows. The left end grouting hole is the left side grouting hole located on the leftmost side, and the right end grouting hole is the right side grouting hole located on the rightmost side.
After the sleeve valve pipe grouting reinforcement process of the reinforced stratum 28 is completed in the step F2, the sleeve valve pipe grouting reinforcement effect of the reinforced stratum 28 needs to be checked by adopting a drilling and coring method;
when the sleeve valve pipe grouting reinforcement effect of the reinforced stratum 28 is checked by adopting a drilling coring method, drilling inspection holes in the reinforced stratum 28 from top to bottom by adopting a drilling coring drilling machine and obtaining drill cores in the inspection holes;
the inspection holes drilled in the consolidated formation 28 are internal inspection holes 26, and the internal inspection holes 26 are grouting inspection holes; the grouting inspection holes are cylindrical drill holes which are vertically arranged and are drilled into the rock stratum 30 from the ground surface from top to bottom, and the hole bottoms of the grouting inspection holes are positioned below the bottom surface of the reinforced stratum 28;
as shown in fig. 5, the number of the inner inspection holes 26 is plural, the plural inner inspection holes 26 are divided into three inspection hole groups from left to right, and each inspection hole group is located between two adjacent left and right columns of the grouting holes 31; each inspection hole group comprises a plurality of inner inspection holes 26 which are arranged on the same vertical plane from back to front along the longitudinal extension direction of the tunnel; the three inspection hole groups are respectively a middle inspection hole group, a left side inspection hole group positioned on the left side of the middle inspection hole group and a right side inspection hole group positioned on the right side of the middle inspection hole group, the left side inspection hole group and the right side inspection hole group are symmetrically distributed on the left side and the right side of the middle inspection hole group, and the middle inspection hole group is positioned on the left side or the right side of a tunnel center line of the constructed shallow tunnel; the inner inspection holes 26 in the middle inspection hole group and the inner inspection holes 26 in the left inspection hole group are arranged in a staggered manner; the left side inspection hole group and the right side inspection hole group are both located on the outer side of the excavation contour line of the constructed shallow tunnel. Thus, the spacing between the left set of inspection holes and the middle set of inspection holes is the same as the spacing between the right set of inspection holes and the middle set of inspection holes.
In this embodiment, the middle inspection hole group includes four grouting inspection holes. The left side inspection hole group comprises a front grouting inspection hole and a rear grouting inspection hole.
During actual construction, the number of the grouting inspection holes and the arrangement positions of the grouting inspection holes in the middle inspection hole group and the number of the grouting inspection holes and the arrangement positions of the grouting inspection holes in the left inspection hole group can be respectively and correspondingly adjusted according to specific requirements.
In this embodiment, when the sleeve valve grouting reinforcement effect of the reinforced stratum 28 is checked by using a drilling coring method, an external inspection hole 27 needs to be drilled outside the reinforced stratum 28 from top to bottom by using a drilling coring drilling machine, and the external inspection hole 27 is located on the left side or the right side of the reinforced stratum 28; the external inspection hole 27 is the grouting inspection hole.
In this embodiment, when the sleeve valve grouting reinforcement effect of the reinforced stratum 28 is checked by using a drilling coring method, a drilling coring drilling machine is further used to drill two inner side middle inspection holes on the left and right sides in the middle of the reinforced stratum 28 from top to bottom, the two inner side middle inspection holes are located on the same cross section of the constructed shallow tunnel, the distances between the inner side middle inspection holes and the front and rear ends of the constructed shallow tunnel are the same, and the inner side middle inspection hole is an inner inspection hole 26; the two inner middle inspection holes are the grouting inspection holes;
one of the inner side middle inspection holes is located on the outer side of the excavation contour line of the constructed shallow tunnel, and the other of the inner side middle inspection holes is located in the excavation contour line of the constructed shallow tunnel.
The height of the hole section at the bottom of the grouting inspection hole in the rock stratum 30 is 0.5-1 m. In this embodiment, the bottom of the grouting inspection hole is located at a hole section height of 0.5m in the rock formation 30. The aperture of the grouting inspection hole is phi 250 mm-phi 350 mm. During actual construction, the height of the hole section at the bottom of the grouting inspection hole in the rock layer 30 and the aperture of the grouting inspection hole can be adjusted correspondingly according to specific requirements.
In this embodiment, the minimum buried depth of the shallow tunnel of burying of being under construction is 15m, and the thickness range of 10m below the earth's surface is the silted soil, and the moisture content is big (in the valley), and the palm face is glutinous old loess, and wherein glutinous old loess is glutinous loess and it is old loess, hard plastics, and the moisture content is big. The water content is 23.1-25.5% by drilling coring detection, the vertical crack develops, the vault falls off after excavation, and is of a massive discrete body structure, and a position 3.5m away from the tunnel bottom is a soil-stone boundary.
And step (3) when sleeve valve pipe grouting advanced reinforcement is carried out on the constructed shallow tunnel, reinforcing the outer left side and the outer right side of the transverse contour line of the constructed shallow tunnel within 3m, reinforcing the upper part of the constructed shallow tunnel within 5m above the vault of the excavation contour line, and reinforcing the bottom of the constructed shallow tunnel to 0.5m below the earth-rock interface. The grouting holes 31 are arranged in a quincunx shape, and 203 grouting holes 31 are formed in total.
When the sleeve valve pipe is adopted for grouting reinforcement in the step one, reinforcement can be performed according to a conventional sleeve valve pipe grouting method. When the grouting is actually carried out, the adopted grout is ordinary single-grout or cement-water glass double-grout. Thus, the adopted grout is cement grout or cement-water glass double-fluid grout.
In this embodiment, as shown in fig. 2, in the first step, the cross section of the tunnel where each row of grouting holes 31 is located is a grouting reinforcement surface of the reinforced stratum 28, the row of grouting holes 31 located at the rearmost side in the reinforced stratum 28 is rear-end grouting holes, and the grouting reinforcement surface where the rear-end grouting holes are located is a rear-end reinforcement surface; each row of the grouting holes 31 comprises a plurality of first-stage grouting holes and a plurality of second-stage grouting holes, and the first-stage grouting holes and the second-stage grouting holes are arranged in a staggered manner;
when grouting sleeve valve pipes is performed in the step F2, grouting reinforcement is performed on the reinforced stratum 28 through the plurality of rows of sleeve valve pipes from back to front along the longitudinal extension direction of the tunnel, and the grouting reinforcement methods of the plurality of rows of sleeve valve pipes are the same;
when grouting reinforcement is carried out on the reinforced stratum 28 through any row of sleeve valve pipes, the sleeve valve pipes are used for grouting reinforcement on the reinforced stratum 28 through the row of sleeve valve pipes for multiple times from first to last, and the grouting reinforcement surface where the row of sleeve valve pipes is located is the current reinforcement surface; when grouting reinforcement is carried out through the sleeve valve pipe, the process is as follows:
step F21, grouting and reinforcing the sleeve valve pipe for the first time: and performing primary grouting reinforcement on the reinforced stratum 28 through the row of sleeve valve pipes, and comprising the following steps of:
step F211, grouting and reinforcing the grouting holes in the first stage: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes, which are positioned in each stage of grouting hole, and the grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
step F212, grouting and reinforcing the second-stage grouting holes: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes in each secondary grouting hole in the step F211, and grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
grouting reinforcement is carried out by adopting a sectional grouting method when grouting reinforcement is carried out through the sleeve valve pipes in any one of the first-stage grouting holes in the step F211 and grouting reinforcement is carried out through the sleeve valve pipes in any one of the second-stage grouting holes in the step F212, the grouting sectional step distance is 50-100 cm, and the grouting speed is 10-100L/min;
in addition, in the step F211 and the step F212, during the grouting process through the sleeve valve pipe in any one of the grouting holes 31, the grouting pressure and the grouting speed of the sleeve valve pipe in the grouting hole 31 are synchronously observed, when the grouting pressure reaches F0 and is kept unchanged for more than 10min or the grouting speed is reduced to be less than 5L/min, the grouting is stopped, the grouting reinforcement process of the sleeve valve pipe in one grouting hole 31 is completed, and the grouting reinforcement termination condition of the grouting hole 31 during the current grouting reinforcement is recorded; wherein F0 is a pre-designed grouting final pressure value, and the value range of F0 is 4 MPa-6 MPa;
the grouting reinforcement termination conditions of each grouting hole 31 are that the grouting pressure reaches the standard or the grouting amount reaches the standard;
when the grouting reinforcement termination condition of any one of the grouting holes 31 is determined, when the sleeve valve pipe in the grouting hole 31 stops grouting, the grouting pressure of the sleeve valve pipe reaches a design final pressure value F0 and is kept unchanged for more than 10min, and the grouting reinforcement termination condition of the grouting hole 31 is judged to be that the grouting pressure reaches the standard; when the sleeve valve pipe in the grouting hole 31 stops grouting, the grouting speed of the sleeve valve pipe is reduced to be below 5L/min, and the grouting reinforcement termination condition of the grouting hole 31 is judged to be that the grouting amount reaches the standard;
step F213, grouting and reinforcing the sleeve valve pipe to finish judgment: judging the grouting reinforcement termination conditions of all grouting holes 31 in the reinforced stratum 28 during the current grouting reinforcement recorded in the step F211 and the step F212: when the grouting reinforcement termination conditions of all the grouting holes 31 in the reinforced stratum 28 at the time of the current grouting reinforcement recorded in step F211 and step F212 are that the grouting pressure reaches the standard, it is determined that the sleeve valve pipe grouting reinforcement process of the current reinforcement surface is completed, and the process proceeds to step F24; otherwise, go to step F22;
step F22, grouting and reinforcing the sleeve valve pipe for the next time: and performing next grouting reinforcement on the reinforced stratum 28 through the row of sleeve valve pipes, wherein the grouting reinforcement comprises the following steps:
step F221, grouting and reinforcing the grouting holes in the first stage: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes, which are positioned in each stage of grouting hole, and the grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
step F222, grouting and reinforcing the second-stage grouting holes: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes in each secondary grouting hole in the step F221, and grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
grouting reinforcement is carried out by adopting a sectional grouting method when grouting reinforcement is carried out through the sleeve valve pipe in any one of the first-stage grouting holes in the step F221 and grouting reinforcement is carried out through the sleeve valve pipe in any one of the second-stage grouting holes in the step F222, the grouting sectional step distance is 50 cm-100 cm, and the grouting speed is 10L/min-100L/min;
in addition, in the step F221 and the step F222, during the grouting process through the sleeve valve pipe in any one of the grouting holes 31, the grouting pressure and the grouting speed of the sleeve valve pipe in the grouting hole 31 are synchronously observed, when the grouting pressure reaches a design final pressure value F0 and is kept unchanged for more than 10min or the grouting speed is reduced to be less than 5L/min, the grouting is stopped, the grouting reinforcement process of the sleeve valve pipe in one grouting hole 31 is completed, and the grouting reinforcement termination condition of the grouting hole 31 during the current grouting reinforcement is recorded;
step F223, grouting and reinforcing the sleeve valve pipe to finish judgment: judging the grouting reinforcement termination conditions of all grouting holes 31 in the reinforced stratum 28 during the current grouting reinforcement recorded in the step F221 and the step F222: when the grouting reinforcement termination conditions of all the grouting holes 31 in the reinforced stratum 28 at the time of the current grouting reinforcement recorded in step F221 and step F222 are that the grouting pressure reaches the standard, determining that the grouting reinforcement process of the sleeve valve pipe of the current reinforcement surface is completed, and entering step F24; otherwise, go to step F23;
step F23, returning to the step F22, and carrying out next grouting reinforcement on the reinforced stratum 28 through the row of sleeve valve pipes;
step F24, grouting and reinforcing the next row of sleeve valve pipes: grouting and reinforcing the reinforced stratum 28 through the sleeve valve pipes in the next row according to the method from the step F21 to the step F23;
step F25, grouting and reinforcing the reinforced stratum and judging: judging whether the sleeve valve pipe grouting reinforcement process of the rear end reinforcement surface in the reinforced stratum 28 is finished or not, judging that the sleeve valve pipe grouting reinforcement process of the reinforced stratum 28 is finished when the sleeve valve pipe grouting reinforcement process of the rear end reinforcement surface in the reinforced stratum 28 is finished through judgment, and entering the step two; otherwise, return to step F24.
When the sectional grouting method is adopted for grouting, the length of each section of grouting is called grouting step distance (also called grouting sectional step distance).
According to the common knowledge in the field, the sleeve valve pipe grouting method is a grouting method initiated by the French Soletanoche basic engineering company in the last 50 th century, and is also called Soletanoche method; the sleeve valve pipe grouting method has the characteristics of better control of grouting range and grouting pressure, repeated grouting, low possibility of grout leakage and grout string generation and the like, and is considered as one of the most reliable grouting methods at home and abroad. The sleeve valve pipe grouting method adopts a sleeve valve pipe to perform grouting, and the sleeve valve pipe structure mainly comprises a phi 48mm PVC outer pipe, a rubber sleeve, a plug, a joint, a cap, a 6-point galvanized grouting linking pipe, a grouting device grout stop ring and the like. The sleeve valve pipe grouting is to set a drill hole in a soil body, pour casing materials after the drilling is finished, place the sleeve valve pipe after the hole bottom returns slurry, permanently keep the sleeve valve pipe in the soil, set slurry outlet holes at intervals at the lower part of the sleeve valve pipe, and set a plugging device outside the slurry outlet holes. During grouting, the grouting pipe with the flow limiting valve is placed into the sleeve valve pipe, and the part needing grouting is grouted. The grout takes a drilled hole as a center and forms a tree root reticular grout vein complex in soil body cracks.
In this embodiment, when sleeve valve pipe grouting reinforcement is performed on the stratum 28 to be reinforced through the plurality of rows of sleeve valve pipes in step F2, the slurry diffusion radius is 1.1m, the grouting slurry is cement slurry, and the water-cement ratio of the cement slurry is 0.8: 1.
In the step F1, when a sleeve valve pipe is installed in each formed grouting hole 31, the sleeve valve pipes are put into the grouting holes 31 in sections until the grouting holes 31 reach the bottom of the grouting holes 31, and then quick setting cement mortar is used between the orifice of the grouting holes 31 and the sleeve valve pipes for filling and blocking to prevent grouting during grouting. And after the sleeve valve pipe is installed, injecting a sleeve shell material. In the embodiment, the shell material is formed by uniformly mixing water, lime and loess according to the weight ratio of (1.5-1.6) to 1: 1.
When sleeve valve pipe grouting advanced reinforcement is carried out in the first step, the tunnel body 1 of the constructed shallow tunnel is reinforced, and meanwhile, the tunnel bottom of the constructed shallow tunnel is reinforced, so that the bearing capacity of the tunnel base can be effectively improved, and the problems of weak foundation, large settlement deformation and the like of the constructed shallow tunnel are effectively solved. Because the cross section of the tunnel where each row of grouting holes 31 is located is a grouting reinforcement surface of the reinforced stratum 28, when the reinforced stratum 28 is reinforced in advance from back to front, a plurality of grouting reinforcement surfaces are reinforced by grouting from back to front along the longitudinal extension direction of the tunnel, and the reinforcing effect is good.
In this embodiment, before the sleeve valve pipe grouting advanced reinforcement in the first step, a layer of concrete is sprayed on the tunnel face of the shallow tunnel to be constructed to seal the tunnel face.
In order to ensure the construction period, when tunnel excavation and primary support are carried out in the second step, in the process of sleeve valve pipe grouting advanced reinforcement in the first step, excavating the constructed shallow tunnel from back to front along the longitudinal extension direction of the tunnel, wherein the excavation surface of the constructed shallow tunnel is positioned behind the grouting reinforcement surface for currently carrying out sleeve valve pipe grouting reinforcement; and the distance between the excavation surface of the constructed shallow tunnel and the grouting reinforcement surface for grouting reinforcement of the sleeve valve pipe is larger than 15 m. Wherein, the excavation surface of the constructed shallow tunnel refers to the excavation surface of the upper hole body 1-1.
In this embodiment, when the sleeve valve pipe is used for grouting in the first step, an KBY90/16 hydraulic double-fluid grouting machine is used for grouting, and a retreating type sectional grouting mode is used.
After the first grouting of each hole is finished, the sleeve valve pipe is immediately washed by clear water, so that the smoothness of a pipeline is ensured when the second grouting is carried out, when the grouting amount does not reach the grouting effect due to the serial grouting and the leakage of the first grouting, the secondary grouting is carried out, and the grouting pressure can be properly increased to uniformly diffuse the grout in the stratum if necessary, so that the grouting effect is ensured. After the reinforced stratum 28 is reinforced in advance from back to front through a plurality of rows of the grouting holes 31, the ground surface adopts a vertical coring mode to carry out grouting effect inspection. In addition, when the grouting effect is actually checked, the plurality of grouting checking holes are used for checking, and the checking shows that the weak stratum is tightly filled with the grout, so that the stratum obtains a good improvement effect.
As shown in fig. 6 and 7, the tunnel supporting structure of the constructed shallow tunnel comprises a tunnel advance supporting structure for advance supporting of an arch part of a tunnel cave 1, a tunnel primary supporting structure for primary supporting of the tunnel cave 1 and a tunnel secondary lining arranged on the inner side of the tunnel primary supporting structure, wherein the tunnel advance supporting structure is positioned above the tunnel primary supporting structure, the tunnel primary supporting structure and the tunnel secondary lining are full-section supporting structures for full-section supporting of the tunnel cave 1, and the tunnel secondary lining is a reinforced concrete lining; the cross-sectional area of the tunnel hole 1 is more than 100m2The tunnel hole 1 is divided into an upper hole body 1-1, a middle hole body 1-2 and a lower hole body 1-3 from top to bottom; the upper partThe cave body 1-1 is formed by performing upper step excavation on the constructed loess tunnel from back to front, the middle cave body 1-2 is formed by performing middle step excavation on the constructed loess tunnel from back to front, and the lower cave body 1-3 is formed by performing lower step excavation on the constructed loess tunnel from back to front;
the tunnel primary support structure is divided into an arch wall primary support structure 12 for primary support of an arch wall of the tunnel cave 1 and a primary support inverted arch 13 for primary support of the bottom of the tunnel cave 1, and the tunnel secondary lining is divided into an arch wall secondary lining 14 for supporting the arch wall of the tunnel cave 1 and an inverted arch secondary lining 15 for supporting the bottom of the tunnel cave 1; the inverted arch secondary lining 15 is positioned above a primary supporting inverted arch 13, an inverted arch backfill layer 16 is arranged on the inverted arch secondary lining 15, the upper surface of the inverted arch secondary lining 15 is a horizontal plane, the bottoms of the left side and the right side of the arch wall secondary lining 14 are horizontal planes, the arch wall secondary lining 14 is supported on the inverted arch secondary lining 15 and poured into a whole, and the inverted arch backfill layer 16 is a concrete filling layer;
the tunnel primary support structure comprises a full-section support structure for performing full-section support on the tunnel hole 1, an arch wall net-jet support structure for performing primary support on an arch wall of the tunnel hole 1, an inverted arch primary support structure for performing primary support on the bottom of the tunnel hole 1 and an anchoring system arranged on the outer side of the full-section support structure; the full-section supporting structure comprises a plurality of full-section supporting frames which are arranged from back to front along the longitudinal extension direction of the tunnel, the two adjacent full-section supporting frames at the front and the back are fixedly connected into a whole through a plurality of longitudinal connecting reinforcing steel bars, the longitudinal connecting reinforcing steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal connecting reinforcing steel bars are arranged along the contour line of the full-section supporting frames; the shape of the full-section support frame is the same as the shape of the cross section of the tunnel hole 1, each full-section support frame is formed by splicing an arch wall support arch frame for supporting an arch wall of the tunnel hole 1 and a tunnel inverted arch support frame 2 for supporting the bottom of the tunnel hole 1, the tunnel inverted arch support frame 2 is positioned right below the arch wall support arch frame, the arch wall support arch frame and the tunnel inverted arch frame are positioned on the same tunnel cross section, and the tunnel inverted arch support frame 2 and the arch wall support arch frame form a closed full-section support;
the arch wall mesh-spraying supporting structure and the arch wall steel arch in the full-section supporting structure form an arch wall primary supporting structure 12, and the inverted arch primary supporting structure and the tunnel inverted arch bracket 2 in the full-section supporting structure form a primary supporting inverted arch 13; the inverted arch primary support structure is an inverted arch concrete injection layer 20 injected at the bottom of the tunnel hole 1, and the tunnel inverted arch support 2 is fixed in the inverted arch concrete injection layer 20;
the arch wall supporting arch center consists of an upper arch center 2-1 positioned in an upper hole body 1-1, two middle side brackets 5 symmetrically arranged below the left side and the right side of the upper arch center 2-1 and positioned in a middle hole body 1-2, and two lower side brackets 6 symmetrically arranged below the left side and the right side of the upper arch center 2-1 and positioned in a lower hole body 1-3, wherein the tunnel inverted arch bracket 2 is positioned in a lower hole body 1-3; each middle side bracket 5 is connected between the upper end of one lower side bracket 6 and the upper arch 2-1; the left end of the tunnel inverted arch support 2 is fixedly connected with the bottom of one lower side support 6, and the right end of the tunnel inverted arch support 2 is fixedly connected with the bottom of the other lower side support 6;
the anchoring system comprises a plurality of anchoring groups which are arranged from back to front along the longitudinal extension direction of the tunnel, one anchoring group is uniformly distributed on the outer side of each full-section supporting frame, and each full-section supporting frame and the anchoring group arranged on the full-section supporting frame are arranged on the same cross section of the tunnel 1;
each anchoring group comprises a left group of upper foot-locking anchor pipes 8, a right group of middle foot-locking anchor pipes 9 and a left group of lower foot-locking anchor pipes 10, wherein the left group of upper foot-locking anchor pipes 8, the right group of middle foot-locking anchor pipes 9 and the left group of lower foot-locking anchor pipes 10 are symmetrically arranged at the outer sides of the bottoms of the left side and the right side of the upper arch 2-1; the outer side of the bottom of each middle side bracket 5 is provided with a group of middle locking leg anchor pipes 9, and the outer side of the bottom of each lower side bracket 6 is provided with a group of lower locking leg anchor pipes 10; each group of the upper lock leg anchor pipes 8 comprises an upper lock leg anchor pipe 8 and a lower lock leg anchor pipe 8 which are arranged in parallel, each group of the middle lock leg anchor pipes 9 comprises an upper middle lock leg anchor pipe 9 and a lower middle lock leg anchor pipe 9 which are arranged in parallel, and each group of the lower lock leg anchor pipes 10 comprises an upper lower lock leg anchor pipe 10 which are arranged in parallel; the upper foot-locking anchor pipe 8, the middle foot-locking anchor pipe 9 and the lower foot-locking anchor pipe 10 are all foot-locking anchor pipes which enter the soil layer on the periphery of the tunnel cave 1 from inside to outside and are gradually inclined downwards from inside to outside;
when the second lining construction is carried out in the third step, when the tunnel secondary lining is constructed from back to front, the inverted arch secondary lining 15 is constructed on the constructed primary support inverted arch 13 from back to front, and the inverted arch secondary lining 15 formed by construction is obtained; in the process of constructing the inverted arch secondary lining 15 from back to front, constructing the arch wall secondary lining 14 on the constructed inverted arch secondary lining 15 from back to front, and connecting the constructed arch wall secondary lining 14 and the inverted arch secondary lining 15 positioned below the constructed arch wall secondary lining into a whole to obtain the tunnel secondary lining formed by construction;
in the step, in the process of constructing the inverted arch secondary lining 15 from back to front, after concrete poured in the inverted arch secondary lining 15 is finally solidified, the inverted arch secondary lining 15 and the primary support inverted arch 13 form the tunnel inverted arch structure formed by construction.
The excavation heights of the upper hole body 1-1 and the middle hole body 1-2 are both 3.5 m-4.5 m, a tunnel bottom backfill soil layer 7 is arranged behind the excavation surface of the lower hole body 1-3, and the tunnel bottom backfill soil layer 7 is positioned in the lower hole body 1-3; referring to fig. 8, the tunnel bottom backfill layer 7 is a temporary moving platform for the wet spraying manipulator 21 to move back and forth. Meanwhile, the structural stability of the bottom of the tunnel 1 can be further improved through the backfill soil layer 7 at the bottom of the tunnel.
In this embodiment, the upper surface of the tunnel bottom backfill layer 7 is a horizontal plane, and the upper surface of the tunnel bottom backfill layer 7 is flush with the upper surface of the inverted arch backfill layer 16.
In this embodiment, the upper arch 2-1 and the middle side bracket 5, the middle side bracket 5 and the lower side bracket 6, and the lower side bracket 6 and the tunnel inverted arch bracket 2 are fixedly connected by connecting bolts. And connecting steel plates for mounting the connecting bolts are arranged at the two ends of the upper arch frame 2-1, the two ends of the middle side support 5, the two ends of the lower side support 6 and the two ends of the tunnel inverted arch support 2.
In order to ensure the processing quality and improve the on-site construction efficiency, the full-section support frame adopts factory centralized processing and distribution and meets the requirement of in-place distribution in half an hour on all working faces.
During actual construction, the excavation height of the tunnel hole 1 is 11 m-15 m, and the excavation width of the tunnel hole 1 is 10 m-15 m. And the constructed tunnel is a deep buried tunnel with the buried depth of more than 50 m.
In this embodiment, the excavation height of the tunnel cave 1 is 12m, the height of the upper cave body 1-1 (i.e., the height of the upper step) is 4m, and the height of the middle cave body 1-2 (i.e., the height of the middle step) is 3.5 m. In the actual construction process, the excavation height of the tunnel cave 1, the height of the upper cave body 1-1 and the height of the middle cave body 1-2 can be correspondingly adjusted according to specific requirements.
In order to ensure the safe excavation, the upper cavity body 1-1 adopts a mode of reserving core soil in the middle for excavation, and the top surface clearance height of the core soil in the upper cavity body 1-1 is 1.5 m-1.8 m. Whether core soil is reserved in the excavation process of the middle hole body 1-2 and the lower hole body 1-3 depends on the stability of the tunnel face.
The arch wall mesh-shotcrete supporting structure comprises an arch wall reinforcing mesh piece hung on an arch wall of a tunnel hole 1 and an arch wall concrete spraying layer 19 sprayed on the arch wall of the tunnel hole 1, the arch wall reinforcing mesh piece is fixed on an arch wall steel arch frame, and the arch wall reinforcing mesh piece and the arch wall steel arch frame are fixed in the arch wall concrete spraying layer 19.
In this embodiment, the arch wall concrete spraying layer 19 and the inverted arch concrete spraying layer 20 are both concrete layers formed by spraying with a wet spraying manipulator 21.
During actual construction, the horizontal distance between the rear end of the tunnel bottom backfill soil layer 7 and the excavation surface of the upper hole body 1-1 is not more than 45 m.
In the actual excavation process of the lower hole body 1-3, carrying out primary support on the excavated and molded lower hole body 1-3 in time, and obtaining a primary support inverted arch 13; and after the primary support of the lower hole bodies 1-3 is finished, backfilling the tunnel bottom backfill soil layer 7 on the primary support inverted arch 13 in time. When the tunnel bottom backfill soil layer 7 is backfilled, the tunnel bottom backfill soil layer 7 is backfilled by using hole slag (namely, muck) in the lower hole bodies 1-3.
During the excavation process of the upper cavity 1-1, the middle cavity 1-2 and the lower cavity 1-3, the excavation slag formed by excavation is loaded to a dump truck by adopting an excavator and is transported out by the dump truck. When the excavated hole slag is transported outwards, the hole slag used for backfilling the tunnel bottom backfill soil layer 7 needs to be reserved, and the reserved hole slag is placed on one side of the inner side of the lower hole body 1-3 so as to be convenient for backfilling the tunnel bottom backfill soil layer 7 in time.
In this embodiment, a plurality of full-section support frames in the full-section support structure are uniformly distributed, and a distance between two adjacent front and rear full-section support frames is L, where a value of L ranges from 0.5m to 1 m.
During actual construction, the distance between two adjacent front and rear full-section support frames (namely the value of L) can be correspondingly adjusted according to specific requirements.
In order to ensure the anchoring effect, in the embodiment, the included angles between the middle and lower lock leg anchor tubes 9 and 10 and the vertical plane are both 45 °.
The upper arch 2-1 is arc-shaped, and the included angle between each upper lockpin anchor pipe 8 and the arch tangent plane of the upper arch 2-1 at the connecting position of the upper lockpin anchor pipe is 45 degrees; the tangent plane of the arch frame is a plane which is vertically arranged with the outer contour line of the upper arch frame 2-1. The tangent plane of the upper arch 2-1 at the position where each upper lock leg anchor pipe 8 is connected is a plane which is vertically arranged with the outer contour line of the upper arch 2-1 at the position where the upper lock leg anchor pipe 8 is connected.
In this embodiment, the arch wall supporting arch frame and the tunnel inverted arch support 2 are all grid steel frames.
And a foamed aluminum pad or a concrete pad is padded at the bottom of each lower side bracket 6 to control displacement and settlement.
As shown in fig. 6, excavating the constructed loess tunnel from back to front along the longitudinal extension direction of the tunnel, and synchronously performing primary support on the tunnel 1 formed by excavation from back to front in the excavation process to obtain the primary support structure of the tunnel formed by construction; and in the primary support process of the tunnel hole 1 formed by excavation from back to front, the secondary lining of the tunnel is constructed in the constructed primary support structure of the tunnel from back to front synchronously.
In the third step, in the process of constructing the inverted arch secondary lining 15 from back to front, the inverted arch backfill layer 16 is constructed on the constructed inverted arch secondary lining 15 from back to front along the longitudinal extension direction of the tunnel.
In this embodiment, when the tunnel excavation and the preliminary bracing are performed in the second step, the method includes the following steps:
step B1, excavating an upper cavity and performing primary support: excavating an upper cavity body 1-1 of the constructed loess tunnel from back to front along the longitudinal extension direction of the tunnel;
in the excavation process of the upper cavity 1-1, performing net-spraying support on an arch part of the upper cavity 1-1 formed by excavation from back to front, and meanwhile, installing an upper arch frame 2-1 in the upper cavity 1-1 formed by excavation from back to front to finish the excavation and primary support construction process of the upper cavity 1-1;
step B2, excavating a middle cavity and performing primary support: b1, excavating the middle hole body 1-2 below the excavated and molded upper hole body 1-1 from back to front along the longitudinal extension direction of the tunnel in the process of excavating the upper hole body and primary supporting;
in the middle hole body 1-2 excavation process, respectively carrying out net-spraying support on the left side and the right side of the middle hole body 1-2 formed by excavation from back to front, and simultaneously respectively installing middle side brackets 5 on the left side and the right side of the middle hole body 1-2 formed by excavation from back to front, and enabling each middle side bracket 5 to be fixedly connected with the upper arch frame 2-1 in the step B1 into a whole, so that the excavation and primary support construction processes of the middle hole body 1-2 are completed;
in the step, the excavation surface of the middle hole body 1-2 is positioned behind the excavation surface of the upper hole body 1-1, and the horizontal distance between the excavation surfaces is 4-6 m;
step B3, excavating a lower cavity and performing primary support: b2, excavating the lower cavity 1-3 below the excavated and molded middle cavity 1-2 from back to front along the longitudinal extension direction of the tunnel in the process of excavating the middle cavity and primary supporting;
in the process of excavating the lower cavity 1-3, respectively carrying out net-spraying support on the left side and the right side of the excavated lower cavity 1-3 from back to front, and synchronously respectively installing lower side brackets 6 on the left side and the right side of the excavated lower cavity 1-3 from back to front in the net-spraying support process, so that each lower side bracket 6 is fixedly connected with the middle side bracket 5 in the step B2 into a whole; meanwhile, a tunnel inverted arch support 2 is arranged at the bottom of the lower hole body 1-3 from back to front, and the arranged tunnel inverted arch support 2 is fixedly connected with lower side supports 6 arranged at the left side and the right side of the lower hole body 1-3 into a whole; in the installation process of the tunnel inverted arch support 2, synchronously spraying a layer of concrete at the bottom of the tunnel hole 1 from back to front to form an inverted arch concrete spraying layer 20, and fixing the tunnel inverted arch support 2 in the inverted arch concrete spraying layer 20 to finish the excavation and primary support construction process of the lower hole body 1-3;
in the step, the excavation surface of the lower cavity 1-3 is positioned behind the excavation surface of the middle cavity 1-2, and the horizontal distance between the excavation surfaces is 4-6 m;
in the step, in the excavation process of the lower hole body 1-3 from back to front, the tunnel hole 1 formed by excavation is obtained; respectively carrying out net-spraying support on the left side and the right side of the lower hole body 1-3 which is formed by excavation from back to front to obtain the constructed and formed arch wall net-spraying support structure; the arch wall mesh-spraying supporting structure is connected with an inverted arch concrete spraying layer 20.
In this embodiment, when the upper hole body 1-1 is excavated in step B1, an excavator with a scarifier is used for excavating, soil layers with a thickness of 30cm to 50cm are reserved on the peripheral sides of the upper hole body 1-1 as manual trimming layers, the manual trimming layers are artificially excavated by using a cutter, so that the excavation precision is ensured, the excavator is strictly prohibited from touching the full-section support frame, the safety and the overexcavation are ensured, and the core soil is reserved when necessary to ensure the stability of the tunnel face.
In the step B1, in the process of installing the upper arch centering 2-1 in the excavated and formed upper cavity 1-1 from back to front, foamed aluminum backing plates or concrete backing plates are respectively arranged at the bottoms of the left side and the right side of each installed upper arch centering 2-1 to control displacement and settlement, and locking anchor pipes 8 are respectively arranged on the left side and the right side of each installed upper arch centering 2-1; meanwhile, a sand cushion layer is paved at the bottom of the left side and the right side of each installed upper arch 2-1 respectively so as to facilitate the bolt connection of the upper arch 2-1 and the middle side bracket 5.
When the middle hole body 1-2 is excavated in the step B2, an excavator with a scarifier is adopted for excavating, soil layers with the thickness of 30 cm-50 cm are reserved on the left side, the right side and the bottom of the middle hole body 1-2 to serve as manual trimming layers, machinery is strictly forbidden to excavate to the side at one time, the manual trimming layers are manually excavated by adopting a cutter, the excavation precision is ensured, the excavator is strictly forbidden to touch the full-section supporting frame, the safety is ensured, the overexcavation is prevented, and core soil is reserved if necessary to ensure the stability of the tunnel face.
In the step B2, in the process of respectively installing the middle side brackets 5 on the left side and the right side of the excavated and formed middle hole body 1-2 from back to front, a foamed aluminum pad or a concrete pad is respectively arranged at the bottom of each installed middle side bracket 5 to control displacement and settlement, and a middle locking anchor pipe 9 is respectively arranged on the outer side of each installed middle side bracket 5; meanwhile, a layer of sand cushion is paved at the bottom of each installed middle side bracket 5 respectively so as to facilitate the bolt connection of the middle side bracket 5 and the lower side bracket 6.
And B3, when the lower hole body 1-3 is excavated, excavating by adopting an excavator with a scarifier, reserving soil layers with the thickness of 30-50 cm on the left side, the right side and the bottom of the lower hole body 1-3 as manual trimming layers, strictly forbidding mechanical excavation to reach the edges at one time, excavating the manual trimming layers by adopting a cutter manually, ensuring the excavation precision, strictly forbidding the excavator to touch the full-section supporting frame, ensuring safety and preventing overexcavation, and reserving core soil if necessary to ensure the stability of the tunnel face.
In the step B3, in the process of respectively installing the lower side brackets 6 on the left and right sides of the excavated and formed lower cavity 1-3 from back to front, a foamed aluminum pad or a concrete pad is respectively arranged at the bottom of each installed lower side bracket 6 to control displacement and settlement, and the outer sides of each installed lower side bracket 6 are respectively provided with a lower lock leg anchor pipe 10.
Because the loess tunnel of being under construction adopts the bench method excavation, to the loess tunnel of being under construction in the excavation process, full section support frame is installed step by step and its temporarily can not seal the cyclization, causes the primary support very easily to appear great deformation. The invention adopts the upper foot-locking anchor pipe 8, the middle foot-locking anchor pipe 9 and the lower foot-locking anchor pipe 10 to respectively restrain the arch feet of the upper arch 2-1, the middle side bracket 5 and the lower side bracket 6, can effectively prevent the arch feet of the upper arch 2-1, the middle side bracket 5 and the lower side bracket 6 from rotating and moving, improves the integral stability of the steel frame, and prevents the initial expenditure from larger deformation.
In this embodiment, the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are all seamless steel pipes with a wall thickness of 5mm, a length of 4m and a diameter of phi 42mm, and the inner ends of the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are all welded and fixed on the full-section support frame through connecting steel bars. The lengths and the driving angles of the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are reasonable in design, so that the deformation of surrounding rock is limited, and the bearing capacity of a supporting structure is exerted. In addition, the number of the upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 at each anchoring position is two, so that the anchoring effect can be further improved.
The upper lock leg anchor pipe 8, the middle lock leg anchor pipe 9 and the lower lock leg anchor pipe 10 are inclined anchor pipes, when the inclined anchor pipes are installed, drill holes installed in the inclined anchor pipes firstly, and due to the fact that the operation space is limited, in order to practically and effectively guarantee the drilling depth and angle of the lock leg anchor pipes, drilling is conducted by adopting a 'three-time drilling method', drill rods with the lengths of 2m, 3m and 4m are selected in sequence, and the drilling depth is gradually drilled to the designed depth according to the sequence of 1.5m, 2.5m and 4 m. And after the drilling is finished, the inclined anchor pipe is installed, and the inclined anchor pipe is directly driven into the drilled hole by using a pipe receiving and conveying device of a rock drill during installation.
In this embodiment, when the excavation and the primary support of the upper cavity are performed in step B1, the excavation footage of the upper cavity 1-1 is 2L to 3L;
when the middle hole body is excavated and initially supported in the step B2, the excavation footage of the middle hole body 1-2 is 2L-3L;
and B3, when the lower cavity is excavated and initially supported, the excavation footage of the lower cavity 1-3 is 2L-3L.
In the embodiment, when the arch part of the upper cavity 1-1 is subjected to net-spraying support from back to front in the step B1, firstly, an arch part reinforcing steel net piece is hung on the arch part of the upper cavity 1-1 from back to front, meanwhile, an upper arch frame 2-1 is installed in the upper cavity 1-1 from back to front, and the hung arch part reinforcing steel net piece is tightly connected with the installed upper arch frame 2-1; spraying a layer of concrete on the inner wall of the upper hole body 1-1 formed by excavation from back to front to form an arch concrete spraying layer, and fixing the hung arch reinforcing mesh and the installed upper arch frame 2-1 in the arch concrete spraying layer to finish the excavation and primary support construction process of the upper hole body 1-1;
when the left side and the right side of the middle hole body 1-2 are respectively supported by the net spraying from back to front in the step B2, respectively hanging middle reinforcing mesh sheets on the left side and the right side of the middle hole body 1-2 from back to front, respectively installing middle side brackets 5 on the left side and the right side of the middle hole body 1-2 from back to front, respectively, and fixedly connecting the hung middle reinforcing mesh sheets with the installed middle side brackets 5, and simultaneously fixedly connecting the hung middle reinforcing mesh sheets with the arch reinforcing mesh sheets in the step B1; respectively spraying a layer of concrete on the inner walls of the left side and the right side of the middle hole body 1-2 from back to front to form a middle concrete spraying layer, connecting the middle concrete spraying layer with the arch concrete spraying layer in the step B1, fixing the hung middle reinforcing mesh and the installed middle side support 5 in the middle concrete spraying layer, and completing the excavation and primary support construction process of the middle hole body 1-2;
when the left and right sides of the lower cavern 1-3 are respectively supported by the net spraying from back to front in the step B3, respectively hanging lower reinforcing mesh sheets on the left and right sides of the lower cavern 1-3 from back to front, respectively installing lower side brackets 6 on the left and right sides of the lower cavern 1-3 from back to front, respectively, and fixedly connecting the hung lower reinforcing mesh sheets with the installed lower side brackets 6, and simultaneously fixedly connecting the hung lower reinforcing mesh sheets with the middle reinforcing mesh sheets in the step B2; respectively spraying a layer of concrete on the inner walls of the left side and the right side of the lower hole body 1-3 from back to front to form a lower concrete spraying layer, connecting the lower concrete spraying layer with the middle concrete spraying layer in the step B2, fixing the hung lower reinforcing mesh and the installed lower side bracket 6 in the lower concrete spraying layer, completing the mesh spraying and supporting process of the left side and the right side of the lower hole body 1-3, and obtaining the constructed and molded arch wall mesh spraying and supporting structure;
the arch part steel bar meshes in the step B1, the middle steel bar meshes in the step B2 and the lower steel bar meshes in the step B3 are connected from top to bottom to form the arch wall steel bar meshes, and the arch part concrete spray layer in the step B1, the middle concrete spray layer in the step B2 and the lower concrete spray layer in the step B3 are connected from top to bottom to form the arch wall concrete spray layer 19.
As shown in fig. 7, in the present embodiment, the excavation footage of the upper cavity 1-1 in step B1, the excavation footage of the middle cavity 1-2 in step B2, and the excavation footage of the lower cavity 1-3 in step B3 are the same;
when tunnel excavation and primary support are carried out in the second step, the wet-spraying mechanical arm 21 moves forwards for multiple times along the longitudinal extension direction of the tunnel through the tunnel bottom backfill soil layer 7, and the distance of each forward movement is the same as the excavation footage of the lower hole bodies 1-3;
after the wet-spraying manipulator 21 moves forwards to a proper position each time, the length of the excavated and molded lower hole body 1-3 in front of the tunnel bottom backfill layer 7 is the same as the excavation footage of the lower hole body 1-3, and the excavated and molded lower hole body 1-3 in front of the tunnel bottom backfill layer 7 is the currently excavated lower hole body;
after the wet spraying mechanical arm 21 moves forwards to the right position each time, the wet spraying mechanical arm 21 is adopted to synchronously spray the lower concrete spraying layer and the inverted arch concrete spraying layer 20 in the currently excavated lower hole body from back to front, and the excavation and primary support construction processes of the currently excavated lower hole body are completed at the same time; after the excavation and primary support construction process of the currently excavated lower hole body is completed, constructing a tunnel bottom backfill soil layer 7 on the primary support inverted arch 13 which is constructed and formed in the currently excavated lower hole body, wherein the constructed tunnel bottom backfill soil layer 7 is a moving platform for the wet spraying manipulator 21 to move forwards next time;
after the lower concrete spraying layer and the inverted arch concrete spraying layer 20 in the currently excavated lower hole body are sprayed, respectively spraying concrete to the upper hole body 1-1 and the middle hole body 1-2 which are positioned in front of the currently excavated lower hole body and are formed by excavation at the moment by adopting a wet spraying manipulator 21 from back to front, and simultaneously completing the excavation and primary support construction process of the upper hole body 1-1 and the middle hole body 1-2 positioned in front of the currently excavated lower hole body;
and after the concrete in the upper and middle excavated and formed hole bodies 1-1 and 1-2 which are positioned in front of the currently excavated lower hole body is sprayed, moving the wet spraying manipulator 21 forwards for the next time.
From the above, the construction process of the primary support inverted arch 13 and the excavation process of the lower hole body 1-3 are carried out synchronously, so that the excavation of the lower hole body 1-3 and the construction of the primary support inverted arch 13 are carried out synchronously, the primary support can be ensured to be sealed and looped in time, the primary support can be ensured to be sealed and looped in the shortest time, the excessive deformation of surrounding rocks is prevented, and the construction safety is ensured. And after the primary support is sealed into a ring, the convenience is improved for the large-scale machinery to move in the hole, so that the requirement of large-scale mechanized construction can be met to the maximum extent, the labor intensity is reduced, the synchronous operation of an upper step, a middle step and a lower step is realized, the full-section flow construction is realized, the construction efficiency can be effectively improved, the engineering cost is reduced, and the aims of safe, economic and efficient construction are fulfilled. Therefore, the horizontal distance between the progress of the primary support inverted arch 13 closed ring formation (namely the primary support closed ring formation) and the excavation surface of the upper hole body 1-1 is 8 m-10 m, so that the safety, reliability and smoothness of the tunnel excavation process can be ensured, and the stability of the large-section loess tunnel can be ensured.
In addition, the horizontal distance between the progress of the closed looping of the primary support inverted arch 13 (namely the closed looping of the primary support) and the excavated surface of the upper hole body 1-1 is 8 m-10 m, so that the working length of the wet spraying manipulator 21 can be ensured to meet the construction requirement, and the wet spraying manipulator 21 can be ensured to spray concrete to the upper hole body 1-1 in front.
In this embodiment, the thickness of each of the arch wall concrete spray layer 19 and the inverted arch concrete spray layer 20 is 30cm, and C25 concrete is used.
The wet spraying manipulator 21 is a mobile concrete spraying manipulator. In this embodiment, the wet spraying manipulator 21 is an HPS301 3016S type wet spraying manipulator (also called HPS3016 tire type concrete spraying trolley) produced by the china iron re-engineering group ltd or a TKJ-20 type wet spraying manipulator (also called TKJ-20 type concrete spraying manipulator) produced by the china iron and rock frontier science and technology ltd.
In this embodiment, the excavation heights of the upper cavity 1-1 and the middle cavity 1-2 can both satisfy the operation space of the wet spraying manipulator 21.
When the step with the reserved core soil is excavated, excavation or local trimming is carried out before the concrete is sprayed, so that the wet spraying mechanical arm 21 has enough normal working space.
When the arch wall concrete spraying layer 19 and the inverted arch concrete spraying layer 20 are sprayed, the primary spraying is firstly carried out, and then the secondary spraying is carried out. When the initial spraying is actually carried out, the spraying is started from one side arch springing along the tunnel excavation section, and the spraying is finished from the arch part to the other side arch springing; the spraying thickness should be controlled at 10-15 cm of side wall and 5-10 cm of arch part when spraying for the first time.
After the initial setting of the initial sprayed concrete, the secondary spraying is carried out according to the sequence from bottom to top. When the inverted arch is sprayed, the middle part of the inverted arch is firstly sprayed and then the two sides of the inverted arch are sprayed, and the thickness of the middle spraying is larger than that of the two sides of the inverted arch.
And when the side wall is re-sprayed, directly spraying to the designed thickness on the basis of primary spraying for the first time. The thickness of each spraying of the arch part is controlled to be 4-5 cm, and the interval of each spraying is 5-10 min, so that the rebound quantity can be greatly reduced. In the spraying process, the distance between the nozzle and the sprayed surface is preferably 1.0 cm-1.5 m, and the nozzle moves continuously and slowly in the transverse direction or the annular direction in the spraying process. If the sprayed surface is shielded by the steel frame and the reinforcing mesh, the spraying angle of the nozzle and the distance between the nozzle and the sprayed surface are changed according to specific conditions, and the steel frame and the reinforcing mesh are densely sprayed and filled behind the steel frame and the reinforcing mesh. When the crack water leakage occurs on the sprayed surface in the spraying process, the water-free part is firstly sprayed and gradually covered to the water seepage part, the dosage of the accelerating agent can be increased by 0.5-2.0 percent based on the standard dosage when the water seepage part is sprayed, and the total dosage cannot exceed 6.0 percent of the dosage of the cement.
After the concrete is sprayed, moist curing is carried out immediately, and curing is generally carried out for not less than 14 days. The environment temperature of the sprayed concrete operation is not lower than 5 ℃.
For further improving the stability of the loess tunnel bottom of being under construction, two adjacent pin around in the tunnel primary bracing structure all carry out the fastening connection through the longitudinal tie piece that multichannel from left to right laid between the tunnel invert support 2, the multichannel longitudinal tie piece all is the level and lays and its edge the outline line of tunnel invert support is laid.
In this embodiment, the longitudinal connector is a channel steel.
During actual construction, other types of section steel can be adopted as the longitudinal connecting piece.
In this embodiment, in the third step, when the secondary lining 14 of the arch wall is constructed, the secondary lining 14 of the arch wall is constructed by using the two-lining trolley from back to front along the longitudinal extension direction of the tunnel. Therefore, the actual construction is simple and convenient, the construction efficiency is high, and the construction quality is easy to ensure.
The left and right short side walls 18 of the tunnel secondary lining are lining sections at the bottoms of the left and right sides of the arch wall secondary lining 14.
And in the third step, when the secondary lining 14 of the arch wall is constructed, the construction process of the two short side walls 18 is synchronously completed, and the left and right short side walls 18 are also constructed by adopting a two-lining trolley. The two-lining trolley is a conventional lining trolley, and the forming template of the lining trolley is processed according to the cross section shape of the arch wall secondary lining 14. Therefore, the forming template arranged on the two-lining trolley is the forming template of the arch wall secondary lining 14, in particular to an arc-shaped template for forming the inner wall of the arch wall secondary lining 14, and the two-lining trolley has a simple structure and is simple and convenient to construct. In addition, because the upper surface of the inverted arch secondary lining 15 is a horizontal plane, the forming template can be stably supported on the inverted arch secondary lining 15, the support is stable and reliable, and the construction quality of the constructed and formed tunnel secondary lining can be effectively ensured.
Therefore, when the second lining construction and the inverted arch backfilling are actually carried out, the construction progress of the inverted arch secondary lining 15 is faster than that of the arch wall secondary lining 14, so that the stability of the bottom of the constructed loess tunnel can be further ensured, and the sealing and looping time of the tunnel secondary lining can be effectively shortened.
According to the common knowledge in the field, the secondary lining (called secondary lining or secondary lining for short) of the tunnel is a molded concrete or reinforced concrete lining which is applied on the inner side of a primary supporting structure (called primary support or primary support for short) of the tunnel in the tunnel engineering construction, and the molded concrete or reinforced concrete lining and the primary supporting structure of the tunnel form a composite lining together. The tunnel secondary lining comprises a left short side wall 18 and a right short side wall 18, the two short side walls 18 are symmetrically arranged above the left side and the right side of the two-lining inverted arch, and the short side walls 18 are a term in the secondary lining of the railway tunnel and are also called as small side walls. Tunnel secondary lining is by lining cutting at the bottom of the tunnel and laying two lining arch wall lining cutting directly over the tunnel invert are connected and are formed, lining cutting at the bottom of the tunnel is by two lining arches and two short side wall 18 connects and constitutes, lining cutting also is called the tunnel invert at the bottom of the tunnel, therefore two short side wall 18 does a part of tunnel invert, the tunnel invert sets up the reverse arch structure in the tunnel bottom for improving upper portion supporting structure atress condition, is one of tunnel structure's main component part. The two short side walls 18 are symmetrically arranged above the left side and the right side of the two lining arch arches, the bottoms of the left side and the right side of the lining of the two lining arch walls are connected with the two lining arch arches through the short side walls 18, the lining of the tunnel bottom and the lining of the two lining arch walls are both reinforced concrete lining, and the cross sections of the two lining arch walls are both arched.
At present, when the composite lining of the tunnel is constructed, a method of constructing an initial support and the two lining inverted arches together is generally adopted, short side walls 18 with a certain height are constructed on the two lining inverted arches, and then inverted arch filling is carried out, so that the problems of multiple construction procedures, low efficiency and the like exist. Meanwhile, since the inverted arch filling should be poured after the concrete of the two-lined inverted arch is finally set, and the arc shape of the two-lined inverted arch must be ensured, this requires that the construction of the two-lined inverted arch and the short-side wall 18 must be formed by means of a formwork, otherwise the inverted arch construction will have the following problems: first, it is not well formed; secondly, the vibration is difficult to carry out, because the concrete slides down towards the bottom once vibrated. In addition, at present, few tunnel construction adopt the inverted arch template, often only install short side wall side form at the inverted arch top surface position of filling, inverted arch fill with two lining inverted arches pour simultaneously. After the inverted arch is filled in place, workers shovel the concrete into the short side wall formwork and do little inserting and tamping and dare not to vibrate. As a result, the quality of the short side wall 18 is greatly compromised, and the concrete filled in the two inverted arches and the inverted arch are different in grade, and the concrete filled in the two inverted arches is poured into the tunnel bottom first and then poured into the inverted arch, and the two concrete are mixed together. Since the short side wall 18 is originally an inverted arch of the tunnel, but filled with concrete, and not vibrated, the strength of the short side wall 18 is substantially low. Moreover, as can be seen from the removal of the mold, the surface of the honeycomb is serious, the appearance quality is barely seen, and the honeycomb is only covered by applying prepared cement paste; the problems of repeated utilization of the templates, unevenness, no finishing, no coating of a release agent and the like exist, and the step line type of the constructed and formed low-side wall 18 is extremely poor, so that the templates of the two-lining trolley are not tightly contacted with the template, and the slab staggering and the slurry leakage are serious. Therefore, the secondary lining structure is properly optimized, and the construction efficiency can be effectively improved on the premise of ensuring the safety of the tunnel structure, so that the project is more economic and reasonable.
In this embodiment, two of the short side walls 18 are lining segments at the bottom of the left and right sides of the arch wall secondary lining 14, and thus two of the short side walls 18 are a part of the arch wall secondary lining 7.
In order to ensure the construction quality of the inverted arch secondary lining 15 and the short side wall 18 and effectively improve the construction efficiency, the interface of the inverted arch secondary lining 15 and the inverted arch filling layer 16 is adjusted to be a plane, and the inverted arch filling layer 16 and the inverted arch secondary lining 15 can be poured simultaneously, so that the construction process of the inverted arch secondary lining 15 and the inverted arch filling layer 16 can be greatly simplified, the concrete of the inverted arch secondary lining 15 and the inverted arch filling layer 16 cannot be mixed into a whole, the construction quality of the inverted arch secondary lining 15 and the inverted arch filling layer 16 can be effectively ensured, and the problems that the construction quality of the inverted arch secondary lining 15 and the inverted arch filling layer 16 cannot be ensured and the like due to different concrete grades are solved. Meanwhile, the upper surface of the inverted arch secondary lining 15 is a horizontal plane, the arc shape of the inverted arch secondary lining 15 does not need to be guaranteed in the concrete pouring process, an arc-shaped template does not need to be adopted, pouring is convenient and simple to achieve by a large margin, pouring is simple and convenient, and the construction quality of the inverted arch secondary lining 15 is easy to guarantee.
Left and right sides symmetry is provided with ditch cable duct 23 in the two lining linings in tunnel, ditch cable duct 23 is for the ditch groove that is used for drainage and cabling of predesigned in advance in the loess tunnel 1 of being under construction. In this embodiment, the inverted arch filler 16 is disposed between the two ditch cable grooves 23. Two ditch cable duct 23 symmetry supports in the left and right sides top of invert secondary lining 15, two ditch cable duct 23 symmetry lays in the left and right sides of invert filling layer 16.
When the upper surface of the inverted arch secondary lining 15 is cast into a plane and the height of the upper surface of the inverted arch secondary lining 15 is determined, the intersection point between the inner contour of the tunnel inverted arch (i.e., the designed inner contour of the tunnel inverted arch, which is an arc-shaped contour) designed in advance and the bottom of the trench cable groove 23 designed in advance is determined, and the intersection points between the upper surface of the inverted arch secondary lining 15 and the designed inner contour of the tunnel inverted arch and the bottom of the trench cable groove 23 designed in advance are arranged on the same horizontal plane. In this embodiment, the inverted arch secondary lining 15 is formed by once casting concrete of the same reference number as that of the inverted arch of the tunnel designed in advance, and the inverted arch filling layer 16 is formed by once casting concrete of the same reference number as that of the inverted arch designed in advance. In this embodiment, the inverted arch filler 16 is cast using C20 concrete. The inverted arch secondary lining 15 is cast separately from the inverted arch filler layer 16. And strictly vibrating the inverted arch secondary lining 15 and the inverted arch filling layer 16 in a layering manner according to large-volume concrete in the concrete pouring process.
In this embodiment, when placing the inverted arch secondary lining 15, the movable inverted arch trestle 17 is used for placing the whole inverted arch trestle, and the middle arc part inside the inverted arch secondary lining 15 is optimized to be a horizontal plane.
The invert secondary lining 15 after optimizing makes the whole promotion by a wide margin of the rigidity of tunnel invert structure to need not to install the arc template in the construction, concrete vibrates portably and the quality of vibrating is easily controlled, and the external dimension and the construction quality of invert secondary lining 15 change in the control, and can improve the efficiency of construction of tunnel invert by a wide margin, tunnel secondary lining's seal time shortens greatly to do not have the interference of arc template to make the invert concrete easily vibrate, the concrete quality promotes greatly. In this embodiment, since the upper surface of the inverted arch secondary lining 15 is a horizontal plane, when the concrete is poured into the inverted arch secondary lining 15, it is only necessary to monitor the height of the upper surface of the poured concrete without using a forming template, and when the height of the upper surface of the poured concrete is the same as the height of the upper surface of the inverted arch secondary lining 15, the concrete pouring construction process of the inverted arch secondary lining 15 is completed, so that the construction process of the inverted arch secondary lining 15 can be greatly simplified.
In addition, it should be noted that: according to the invention, the concrete of the inverted arch secondary lining 15 is not only poured into a plane, but the upper surface of the inverted arch reinforcement cage in the inverted arch secondary lining 15 is also set to be a horizontal plane, so that the reinforcement cage is arranged in the whole transverse section of the inverted arch secondary lining 15, and the upper surface of the inverted arch reinforcement cage is a horizontal plane, so that the binding process of the inverted arch reinforcement cage can be effectively simplified.
In this embodiment, the existing two-lined arch wall lining and two short side walls 18 are connected to form the arch wall secondary lining 14, so that the existing two-lined arch wall lining and two short side walls 18 are constructed as an integral lining, and the arch wall secondary lining 14 is constructed by using a two-lined trolley. Therefore, the existing two-lining arch wall lining and two short side walls 18 are formed by one-step construction through a two-lining trolley, the construction efficiency of the tunnel secondary lining can be further improved, the closing time of the tunnel secondary lining is shortened, the ring sealing time of the tunnel secondary lining is shortened, and the structural stability of the constructed loess tunnel is further improved.
In addition, the existing two-lining arch wall lining and the two short side walls 18 are poured into a whole, so that construction joints in the tunnel secondary lining can be effectively reduced, the integrity of the tunnel secondary lining is stronger, and the integral stress effect is better. Meanwhile, the following problems existing in the prior tunnel secondary lining construction method that the inverted arch is constructed in advance and then the combined steel template is used for constructing the short side wall can be effectively solved: firstly, the damage to the constructed double-lined inverted arch possibly caused by the construction process of the short side wall 18 when the short side wall 18 is constructed by utilizing the combined steel template after the inverted arch is constructed in advance is avoided; secondly, in order to prevent the short side wall 18 from damaging the constructed secondary substrate inverted arch 8 in the construction process, the short side wall 18 must be constructed after the secondary substrate inverted arch is finally set, so that the construction efficiency is greatly improved, and the construction period is effectively shortened; and the construction quality and the connection strength of the joint of the third and the short side walls 18 and the second lining inverted arch can be ensured, the construction cost can be effectively saved, the construction efficiency can be further improved, and the later reinforcing measure construction cost and the construction period can be reduced.
The primary pouring length of the inverted arch secondary lining 15 is determined according to the length of a secondary lining trolley for constructing the arch wall secondary lining 14, and the primary pouring length of the inverted arch secondary lining 15 is 2 times or 3 times of the length of the secondary lining trolley (namely the longitudinal length of the primary arch wall secondary lining 14), so that the construction efficiency of the tunnel inverted arch can be greatly improved, and the stability of the constructed loess tunnel 1 is further ensured. In this embodiment, the primary casting length of the inverted arch secondary lining 15 is 2 times of the length of a secondary lining trolley (i.e., the longitudinal length of the secondary lining 14 of the one-ring arch wall), the length of the secondary lining trolley is 12m, and the primary maximum casting length of the inverted arch secondary lining 15 is 24 m.
In the process of excavating the loess tunnel 1 to be constructed, when the inverted arch secondary lining 15 is poured, once excavation is carried out, once bottom cleaning and pouring are carried out in different times, so that the construction interference between working procedures is reduced, the construction joints are reduced, and the construction quality is ensured. And, when carrying out the construction to inverted arch secondary lining 15, clear the end first, then carry out reinforcement, concrete pouring at last.
In the embodiment, the inverted arch secondary lining 15 and the arch wall secondary lining 14 are both reinforced concrete linings;
in the third step, when the inverted arch secondary lining 15 is constructed from back to front, the reinforcement cage in the inverted arch secondary lining 15 is bound on the constructed primary support inverted arch 13 from back to front, and the bound reinforcement cage is an inverted arch reinforcement cage; in the process of binding the inverted arch reinforcement cage from back to front, performing concrete pouring on the inverted arch secondary lining 15 from back to front, pouring the bound inverted arch reinforcement cage in the inverted arch secondary lining 15, and simultaneously, tightly connecting the constructed inverted arch secondary lining 15 and a primary support inverted arch 13 positioned below the inverted arch secondary lining 15 into a whole;
in the third step, when the secondary lining 14 of the arch wall is constructed from back to front, the reinforcement cage in the secondary lining 14 of the arch wall is bound on the constructed inverted arch secondary lining 15 from back to front, and the bound reinforcement cage is tightly connected with the inverted arch reinforcement cage right below the reinforcement cage, and at the moment, the bound reinforcement cage is the reinforcement cage of the arch wall; in the process of binding the arch wall reinforcement cage from back to front, performing concrete casting on an arch wall secondary lining 14 from back to front, so that the bound arch wall reinforcement cage is cast in the arch wall secondary lining 14, the constructed arch wall secondary lining 14 is tightly connected with a primary support inverted arch 13 positioned below the constructed arch wall secondary lining 14 into a whole, and the constructed arch wall secondary lining 14 is tightly connected with an arch wall primary support structure 12 positioned outside the constructed arch wall secondary lining 14 into a whole;
the binding progress of the inverted arch reinforcement cage is faster than that of the arch wall reinforcement cage, and the concrete pouring progress of the inverted arch secondary lining 15 is faster than that of the arch wall secondary lining 14. In this embodiment, the upper surface of the inverted arch reinforcement cage is a horizontal plane.
As shown in fig. 7, in this embodiment, when the second lining construction and the inverted arch backfilling are performed in step three, the construction progress of the inverted arch backfill layer 16 is the same as the construction progress of the inverted arch secondary lining 15, which can effectively accelerate the tunnel construction progress, and the concrete pouring of the inverted arch backfill layer 16 and the inverted arch secondary lining 15 is not affected by each other because the interface between the inverted arch backfill layer 16 and the inverted arch secondary lining 15 is a horizontal plane, and the problem that the construction quality of the inverted arch backfill layer 16 and the inverted arch secondary lining 15 is affected by the mixing of the concrete of the inverted arch backfill layer 16 and the inverted arch secondary lining 15 does not occur.
During actual construction, the inverted arch backfill layer 16 and the inverted arch secondary lining 15 form a tunnel inverted arch and backfill structure, the construction progress of the inverted arch backfill layer 16 and the inverted arch secondary lining 15 is the same, when the tunnel inverted arch and backfill structure are constructed, the adopted forming templates are formed by splicing a left side template 24 and a right side template 24 which are symmetrically arranged and a front template 25 which is used for forming the front side wall of the tunnel inverted arch and backfill structure, a template is not required to be adopted on the upper surface of the inverted arch secondary lining 15, the forming templates are simple in structure, the side templates 24 are rectangular templates and vertical templates which are used for forming the left side wall or the right side wall of the inverted arch backfill layer 16, the two side templates 24 are arranged along the longitudinal extension direction of the tunnel, and the clear distance between the two side templates 24 is the same as the transverse width of the inverted arch backfill layer 16; the heights of the two side templates 24 are not less than the thickness of the inverted arch backfill layer 16, the bottom surfaces of the two side templates 24 are arranged on the same horizontal plane, and the bottom surfaces of the two side templates are flush with the height of the upper surface of the inverted arch secondary lining 15; as shown in fig. 10, the front formwork 25 and the side formwork 24 are vertically arranged, and the front formwork 25 is a vertical formwork for molding the front side wall of the inverted arch backfill layer 16 and the inverted arch secondary lining 15; the front template 25 consists of an upper template and a lower template positioned right below the upper template, the lower template is a template for molding the front side wall of the inverted arch secondary lining 15, the shape and the size of the lower template are the same as the shape and the size of the cross section of the inverted arch secondary lining 15, and the bottom of the lower template is supported on the primary support inverted arch 13; the upper template is a template for molding the front side wall of the inverted arch backfill layer 16, the upper template is a rectangular template, the height of the upper template is not less than the thickness of the inverted arch backfill layer 16, and the bottom surface of the upper template is flush with the upper surface of the inverted arch secondary lining 15. In this embodiment, the upper mold plate and the lower mold plate are processed and manufactured as a whole.
In this embodiment, portable invert trestle 17 includes the trestle body and installs trestle body bottom the shaping template.
In the embodiment, the constructed loess tunnel is divided into a plurality of tunnel sections from back to front along the longitudinal extension direction of the tunnel;
the inverted arch backfill layer 16 and the inverted arch secondary lining 15 form an inverted arch and backfill structure of the tunnel, and when secondary lining construction and inverted arch backfill are carried out in the second step, a movable inverted arch trestle 17 is adopted to construct the inverted arch and the backfill structure of the tunnel from back to front;
when the movable inverted arch trestle 17 is adopted to construct the tunnel inverted arch and the backfill structure from back to front, respectively performing tunnel inverted arch and backfill construction on a plurality of tunnel sections of the constructed loess tunnel from back to front, wherein the length of each tunnel section is not greater than the working length of the movable inverted arch trestle 17; the construction methods of the inverted arches and the backfilling of the tunnel sections are the same;
when any one of the tunnel sections of the constructed loess tunnel is subjected to tunnel inverted arch and backfill construction, the process is as follows:
step A1: horizontally moving the trestle forwards: horizontally moving the movable inverted arch trestle 17 forwards to the construction position of the currently constructed tunnel section along the longitudinal extension direction of the tunnel;
step A2, pouring an inverted arch secondary lining: pouring concrete into the inverted arch secondary lining 15 of the currently constructed tunnel section from bottom to top by adopting the movable inverted arch trestle 17 moved in place in the step A1;
step A3, inverted arch backfilling: after the inverted arch secondary lining is poured in the step A2, concrete is poured on the inverted arch backfill layer 16 of the currently constructed tunnel section from bottom to top by adopting the movable inverted arch trestle 17 which is moved in place in the step A1;
finishing the tunnel inverted arch and backfill construction process of the currently constructed tunnel section after the concretes poured in the step A2 and the step A3 are finally set;
and step A4, returning to the step A1, and performing tunnel inverted arch and backfill construction on one tunnel section.
The movable inverted arch trestle 17 is an inverted arch construction trestle, and because the upper surface of the tunnel bottom backfill layer 7 is flush with the upper surface of the inverted arch backfill layer 16, the tunnel bottom backfill layer 7 and the inverted arch backfill layer 16 form a horizontal moving platform for the movable inverted arch trestle 17 to move. As shown in fig. 7, the movable inverted arch trestle 17 is supported on the tunnel bottom backfill layer 7 at the front side thereof, and supported on the inverted arch backfill layer 16 which is formed by construction at the rear side thereof, so that the actual construction is very simple.
In this embodiment, before any of the tunnel sections of the constructed loess tunnel is subjected to tunnel inverted arch and backfill construction, the tunnel bottom backfill soil layer 7 in the currently constructed tunnel section is cleaned from back to front along the longitudinal extension direction of the tunnel.
In the embodiment, the bottom of the inverted arch reinforcement cage comprises a plurality of arched reinforcements arranged from back to front, each arched reinforcement is positioned on the cross section of one tunnel of the tunnel cave 1, the plurality of arched reinforcements are arranged in parallel, and the shapes of the arched reinforcements are the same as those of the inverted arch secondary lining 15; the left end and the right end of each arch-shaped reinforcing steel bar extend to the positions above the inverted arch secondary lining 15, and the sections, extending from the two ends of each arch-shaped reinforcing steel bar to the positions above the inverted arch secondary lining 15, are reinforcing steel bar exposed sections used for connecting the arch wall reinforcing steel bar cage;
and in the process of binding the arch wall reinforcement cage from back to front, the bound arch wall reinforcement cage is fixedly connected with the reinforcement exposed section below the arch wall reinforcement cage.
As shown in fig. 6 and 7, in the present embodiment, the tunnel advance support structure includes a plurality of small forepoling grouting support structures for advancing the arch part of the tunnel 1 from back to front along the longitudinal extension direction of the tunnel; the structures of the advanced small conduit grouting support structures are the same, and the lap joint length between two adjacent advanced small conduit grouting support structures in the front and back is not less than 0.5 m;
each advanced small conduit grouting supporting structure comprises a plurality of small grouting conduits 22 which are drilled into the soil body in front of the tunnel face of the tunnel cave 1 from back to front and a small conduit guide frame for guiding the small grouting conduits 22, wherein the small grouting conduits 22 are distributed on the same tunnel section from left to right along the arch contour line of the upper tunnel body 1-1; all the small grouting pipes 22 in each advanced small pipe grouting support structure are the same in structure and size; the small guide pipe guide frame is the upper arch frame 2-1, a plurality of guide holes for guiding the small grouting guide pipes 22 are formed in the small guide pipe guide frame, and the guide holes are arranged from left to right along the arch contour line of the upper hole body 1-1.
In this embodiment, the small grouting pipes 22 are hot-rolled seamless steel pipes with a diameter of phi 42mm and a wall thickness of 3.5mm, the small grouting pipes 22 are 3.5m to 4.0m long, the small grouting pipes 22 are arranged in the range of 120 degrees of the arch part 1 of the tunnel, and the circumferential distance between the small grouting pipes 22 is 40 cm. And in the first step, before tunnel excavation and primary support, the advanced small conduit grouting support structure is adopted to advance support the arch part of the constructed tunnel.
The small grouting guide pipe 22 is drilled according to the design requirement, and then the small grouting guide pipe 22 penetrates through the small grouting guide pipe guide frame and is jacked by a hammering or drilling machine, the jacking length is not less than 90% of the total length of the small grouting guide pipe 22, the exposed length is favorable for the access of a grouting pipeline, and sand in a steel pipe is blown out by high-pressure air. And, when adopting the slip casting ductule 22 slip casting, the slip casting liquid is cement mortar to strengthen the intensity of the slip casting ductule 22.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims (10)
1. A construction method of a shallow tunnel in a loess gully is characterized by comprising the following steps:
step one, grouting a sleeve valve pipe and reinforcing in advance: grouting and reinforcing a sleeve valve pipe in a stratum of a construction area where the constructed shallow tunnel is located;
the constructed shallow tunnel is a shallow tunnel which is positioned in the loess gully and penetrates through a loess stratum (29), the stratum of the construction area where the constructed shallow tunnel is located is a reinforced stratum (28), the constructed shallow tunnel is a linear tunnel, and the constructed shallow tunnel and the reinforced stratum (28) are horizontally arranged; the loess stratum (29) is positioned above the rock stratum (30), and an interface between the loess stratum (29) and the rock stratum (30) is a soil-rock interface;
the reinforced stratum (28) is arranged along the longitudinal extension direction of the tunnel of the constructed shallow tunnel, the longitudinal length of the reinforced stratum (28) is the same as that of the constructed shallow tunnel, and the width of the reinforced stratum is larger than the excavation width of the constructed shallow tunnel; the cross section of the reinforced stratum (28) is rectangular, the upper surface of the reinforced stratum (28) is higher than the vault of the constructed shallow tunnel, and the bottom surface of the reinforced stratum (28) is positioned below the earth-rock interface; a plurality of rows of grouting holes (31) for grouting sleeve valve pipes are formed in the reinforced stratum (28), the plurality of rows of grouting holes (31) are arranged from back to front along the longitudinal extension direction of the tunnel, each row of grouting holes (31) comprises a plurality of grouting holes (31) which are vertically arranged and are positioned on the cross section of the same tunnel, and the grouting holes (31) in the front and back adjacent rows of grouting holes (31) are arranged in a staggered manner; all grouting holes (31) in the reinforced stratum (28) are distributed in a quincunx shape and are uniformly distributed, and the distance between every two adjacent grouting holes (31) in the reinforced stratum (28) is 1.8-2.2 m; the grouting holes (31) are cylindrical drilled holes which are vertically arranged and are drilled into the rock stratum (30) from the ground surface from top to bottom, and the bottom of each grouting hole (31) is flush with the bottom surface of the stratum (28) to be reinforced;
when sleeve valve pipe grouting reinforcement is carried out on a reinforced stratum (28), the method comprises the following steps:
step F1, drilling and sleeve valve pipe installation: drilling each grouting hole (31) in a plurality of rows of grouting holes (31) in a reinforced stratum (28), installing a sleeve valve pipe in each formed grouting hole (31), and enabling the bottom of the installed sleeve valve pipe to extend into the bottom of the installed grouting hole (31);
after the multiple rows of grouting holes (31) in the reinforced stratum (28) are drilled and sleeve valve pipes are installed in each grouting hole (31), obtaining multiple rows of sleeve valve pipes which are installed in place;
step F2, grouting sleeve valve tubes: performing sleeve valve pipe grouting reinforcement on the reinforced stratum (28) through the multiple rows of sleeve valve pipes in the step F1 to finish the sleeve valve pipe grouting reinforcement process of the reinforced stratum (28);
step two, tunnel excavation and primary support: excavating the constructed shallow tunnel from back to front along the longitudinal extension direction of the tunnel, and synchronously performing primary support on the tunnel hole (1) formed by excavation from back to front in the excavation process to obtain a primary support structure of the tunnel formed by construction;
step three, second lining construction: and in the second step, in the primary support process of the tunnel hole (1) formed by excavation from back to front, the secondary lining of the tunnel is constructed on the inner side of the constructed primary support structure of the tunnel from back to front along the longitudinal extension direction of the tunnel.
2. The construction method of the shallow tunnel in the loess gully according to claim 1, wherein: the tunnel buried depth of the shallow tunnel constructed in the first step is 15-25 m; the vertical distance between the upper surface of the reinforced stratum (28) and the vault of the constructed shallow tunnel is H, and the value range of H is 4-6 m.
3. The construction method of the shallow tunnel in the loess gully according to claim 1 or 2, wherein: in the step one, the left side wall and the right side wall of the reinforced stratum (28) are symmetrically arranged on the left side and the right side of the constructed shallow tunnel, and the width of the reinforced stratum (28) is 5-8 m larger than the excavation width of the constructed shallow tunnel.
4. The construction method of the shallow tunnel in the loess gully according to claim 1 or 2, wherein: the height of a hole section at the bottom of the grouting hole (31) in the rock stratum (30) is not less than 0.5m, and the hole diameter of the grouting hole (31) is phi 100 mm-phi 120 mm.
5. The construction method of the shallow tunnel in the loess gully according to claim 1 or 2, wherein: all grouting holes (31) in the reinforced stratum (28) are distributed in multiple rows, and each row of grouting holes (31) comprises a plurality of grouting holes (31) which are distributed on the same vertical surface from back to front along the longitudinal extension direction of the tunnel; a row of grouting holes (31) are distributed on the middle line of the constructed shallow tunnel;
after the sleeve valve pipe grouting reinforcement process of the reinforced stratum (28) is completed in the step F2, the sleeve valve pipe grouting reinforcement effect of the reinforced stratum (28) needs to be checked by adopting a drilling and coring method;
when the sleeve valve pipe grouting reinforcement effect of the reinforced stratum (28) is checked by adopting a drilling coring method, drilling inspection holes in the reinforced stratum (28) by adopting a drilling coring drilling machine from top to bottom and obtaining drill cores in the inspection holes;
the method comprises the steps that an inspection hole drilled in a reinforced stratum (28) is an internal inspection hole (26), and the internal inspection hole (26) is a grouting inspection hole; the grouting inspection holes are cylindrical drill holes which are vertically arranged and are drilled into the rock stratum (30) from the ground surface from top to bottom, and the hole bottoms of the grouting inspection holes are positioned below the bottom surface of the reinforced stratum (28);
the number of the internal inspection holes (26) is multiple, the internal inspection holes (26) are divided into three inspection hole groups from left to right, and each inspection hole group is positioned between two adjacent left and right columns of grouting holes (31); each inspection hole group comprises a plurality of inner inspection holes (26) which are arranged on the same vertical plane from back to front along the longitudinal extension direction of the tunnel; the three inspection hole groups are respectively a middle inspection hole group, a left side inspection hole group positioned on the left side of the middle inspection hole group and a right side inspection hole group positioned on the right side of the middle inspection hole group, the left side inspection hole group and the right side inspection hole group are symmetrically distributed on the left side and the right side of the middle inspection hole group, and the middle inspection hole group is positioned on the left side or the right side of a tunnel center line of the constructed shallow tunnel; the inner inspection holes (26) in the middle inspection hole group and the inner inspection holes (26) in the left inspection hole group are arranged in a staggered mode; the left side inspection hole group and the right side inspection hole group are both located on the outer side of the excavation contour line of the constructed shallow tunnel.
6. The construction method of the shallow tunnel in the loess gully according to claim 5, wherein: when the sleeve valve pipe grouting reinforcement effect of the reinforced stratum (28) is checked by adopting a drilling coring method, an external inspection hole (27) needs to be drilled outside the reinforced stratum (28) from top to bottom by adopting a drilling coring drilling machine, and the external inspection hole (27) is positioned on the left side or the right side of the reinforced stratum (28); the external inspection hole (27) is the grouting inspection hole.
7. The construction method of the shallow tunnel in the loess gully according to claim 1 or 2, wherein: in the first step, the cross section of the tunnel where each row of grouting holes (31) are located is a grouting reinforcement surface of a reinforced stratum (28), the row of grouting holes (31) located on the rearmost side in the reinforced stratum (28) are rear end grouting holes, and the grouting reinforcement surface where the rear end grouting holes are located is a rear end reinforcement surface; each row of the grouting holes (31) comprises a plurality of primary grouting holes and a plurality of secondary grouting holes, and the primary grouting holes and the secondary grouting holes are arranged in a staggered manner;
when grouting sleeve valve pipes is performed in the step F2, respectively grouting and reinforcing the reinforced stratum (28) through a plurality of rows of sleeve valve pipes from back to front along the longitudinal extension direction of the tunnel, wherein the grouting and reinforcing methods of the plurality of rows of sleeve valve pipes are the same;
when grouting reinforcement is carried out on the reinforced stratum (28) through any row of sleeve valve pipes, the sleeve valve pipes are used for grouting reinforcement on the reinforced stratum (28) through the row of sleeve valve pipes for multiple times from first to last, and the grouting reinforcement surface where the row of sleeve valve pipes is located is the current reinforcement surface; when grouting reinforcement is carried out through the sleeve valve pipe, the process is as follows:
step F21, grouting and reinforcing the sleeve valve pipe for the first time: and performing primary grouting reinforcement on the reinforced stratum (28) through the row of sleeve valve pipes, and comprising the following steps of:
step F211, grouting and reinforcing the grouting holes in the first stage: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes, which are positioned in each stage of grouting hole, and the grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
step F212, grouting and reinforcing the second-stage grouting holes: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes in each secondary grouting hole in the step F211, and grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
grouting reinforcement is carried out by adopting a sectional grouting method when grouting reinforcement is carried out through the sleeve valve pipes in any one of the first-stage grouting holes in the step F211 and grouting reinforcement is carried out through the sleeve valve pipes in any one of the second-stage grouting holes in the step F212, the grouting sectional step distance is 50-100 cm, and the grouting speed is 10-100L/min;
in addition, in the step F211 and the step F212, during grouting through the sleeve valve pipes in any grouting hole (31), synchronously observing the grouting pressure and the grouting speed of the sleeve valve pipes in the grouting hole (31), stopping grouting when the grouting pressure reaches F0 and keeps unchanged for more than 10min or when the grouting speed is reduced to be less than 5L/min, completing the grouting reinforcement process of the sleeve valve pipes in one grouting hole (31), and recording the grouting reinforcement termination condition of the grouting hole (31) during the current grouting reinforcement; wherein F0 is a pre-designed grouting final pressure value, and the value range of F0 is 4 MPa-6 MPa;
the grouting reinforcement termination conditions of each grouting hole (31) are that the grouting pressure reaches the standard or the grouting amount reaches the standard;
when the grouting reinforcement termination condition of any one grouting hole (31) is determined, when the sleeve valve pipe in the grouting hole (31) stops grouting, the grouting pressure of the sleeve valve pipe reaches a design final pressure value F0 and is kept unchanged for more than 10min, and the grouting reinforcement termination condition of the grouting hole (31) is judged to be that the grouting pressure reaches the standard; when the sleeve valve pipe in the grouting hole (31) stops grouting, the grouting speed of the sleeve valve pipe is reduced to be below 5L/min, and the grouting reinforcement termination condition of the grouting hole (31) is judged to be that the grouting amount reaches the standard;
step F213, grouting and reinforcing the sleeve valve pipe to finish judgment: and F211 and F212, judging the grouting reinforcement termination conditions of all grouting holes (31) in the reinforced stratum (28) during the current grouting reinforcement: when the grouting reinforcement termination conditions of all grouting holes (31) in the reinforced stratum (28) during the current grouting reinforcement recorded in the step F211 and the step F212 are both that the grouting pressure reaches the standard, judging that the sleeve valve pipe grouting reinforcement process of the current reinforcement surface is completed, and entering the step F24; otherwise, go to step F22;
step F22, grouting and reinforcing the sleeve valve pipe for the next time: and performing next grouting reinforcement on the reinforced stratum (28) through the row of sleeve valve pipes, and comprising the following steps of:
step F221, grouting and reinforcing the grouting holes in the first stage: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes, which are positioned in each stage of grouting hole, and the grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
step F222, grouting and reinforcing the second-stage grouting holes: grouting reinforcement is carried out through the sleeve valve pipes in the row of sleeve valve pipes in each secondary grouting hole in the step F221, and grouting reinforcement is symmetrically carried out from the left side to the right side to the middle part;
grouting reinforcement is carried out by adopting a sectional grouting method when grouting reinforcement is carried out through the sleeve valve pipe in any one of the first-stage grouting holes in the step F221 and grouting reinforcement is carried out through the sleeve valve pipe in any one of the second-stage grouting holes in the step F222, the grouting sectional step distance is 50 cm-100 cm, and the grouting speed is 10L/min-100L/min;
in addition, in the step F221 and the step F222, during grouting through the sleeve valve pipes in any grouting hole (31), synchronously observing the grouting pressure and the grouting speed of the sleeve valve pipes in the grouting hole (31), stopping grouting when the grouting pressure reaches a design final pressure value F0 and keeps unchanged for more than 10min or the grouting speed is reduced to be less than 5L/min, completing the grouting reinforcement process of the sleeve valve pipes in one grouting hole (31), and recording the grouting reinforcement termination condition of the grouting hole (31) during the current grouting reinforcement;
step F223, grouting and reinforcing the sleeve valve pipe to finish judgment: and F221 and F222, judging the grouting reinforcement termination conditions of all grouting holes (31) in the reinforced stratum (28) during the current grouting reinforcement: when the grouting reinforcement termination conditions of all grouting holes (31) in the reinforced stratum (28) during the current grouting reinforcement recorded in the step F221 and the step F222 are both that the grouting pressure reaches the standard, judging that the sleeve valve pipe grouting reinforcement process of the current reinforcement surface is completed, and entering the step F24; otherwise, go to step F23;
f23, returning to the step F22, and performing next grouting reinforcement on the reinforced stratum (28) through the row of sleeve valve pipes;
step F24, grouting and reinforcing the next row of sleeve valve pipes: grouting reinforcement of the reinforced stratum (28) through the sleeve valve pipes in the next row according to the method from the step F21 to the step F23;
step F25, grouting and reinforcing the reinforced stratum and judging: judging whether the sleeve valve pipe grouting reinforcement process of the rear end reinforcement surface in the reinforced stratum (28) is finished or not, judging that the sleeve valve pipe grouting reinforcement process of the reinforced stratum (28) is finished when the sleeve valve pipe grouting reinforcement process of the rear end reinforcement surface in the reinforced stratum (28) is finished through judgment, and entering the step two; otherwise, return to step F24.
8. The construction method of the shallow tunnel in the loess gully according to claim 1 or 2, wherein: before sleeve valve pipe grouting advanced reinforcement is carried out in the first step, spraying a layer of concrete on the tunnel face of the constructed shallow tunnel for sealing;
when tunnel excavation and primary support are carried out in the second step, in the process of sleeve valve pipe grouting advanced reinforcement in the first step, excavating the constructed shallow tunnel from back to front along the longitudinal extension direction of the tunnel, wherein the excavation surface of the constructed shallow tunnel is positioned behind the grouting reinforcement surface for currently carrying out sleeve valve pipe grouting reinforcement; and the distance between the excavation surface of the constructed shallow tunnel and the grouting reinforcement surface for grouting reinforcement of the sleeve valve pipe is larger than 15 m.
9. The construction method of the shallow tunnel in the loess gully according to claim 1 or 2, wherein: the tunnel supporting structure of the constructed shallow tunnel comprises a tunnel forepoling structure for forepoling the arch part of a tunnel hole (1), a tunnel primary supporting structure for preliminary supporting the tunnel hole (1) and a tunnel secondary lining distributed on the inner side of the tunnel primary supporting structure, wherein the tunnel forepoling structure is positioned above the tunnel primary supporting structure, the tunnel primary supporting structure and the tunnel secondary lining are full-section supporting structures for supporting the full-section of the tunnel hole (1), and the tunnel secondary lining is a reinforced concrete lining; the cross-sectional area of the tunnel hole (1) is more than 100m2The tunnel hole (1) is divided into an upper hole body (1-1), a middle hole body (1-2) and a lower hole body (1-3) from top to bottom; the upper portion hole body (1-1) is a hole body formed after upper step excavation is carried out on the constructed loess tunnel from back to front, the middle portion hole body (1-2) is a hole body formed after middle step excavation is carried out on the constructed loess tunnel from back to front, and the lower portion hole body (1-3) is a hole body formed after lower step excavation is carried out on the constructed loess tunnel from back to front;
the tunnel primary support structure comprises an arch wall primary support structure (12) for primary support of an arch wall of a tunnel hole (1) and a primary support inverted arch (13) for primary support of the bottom of the tunnel hole (1), and the tunnel secondary lining comprises an arch wall secondary lining (14) for supporting the arch wall of the tunnel hole (1) and an inverted arch secondary lining (15) for supporting the bottom of the tunnel hole (1); the inverted arch secondary lining (15) is positioned above a primary supporting inverted arch (13), an inverted arch backfill layer (16) is arranged on the inverted arch secondary lining (15), the upper surface of the inverted arch secondary lining (15) is a horizontal plane, the bottoms of the left side and the right side of the arch wall secondary lining (14) are horizontal planes, the arch wall secondary lining (14) is supported on the inverted arch secondary lining (15) and poured into a whole, and the inverted arch backfill layer (16) is a concrete filling layer;
the tunnel primary support structure comprises a full-section support structure for performing full-section support on a tunnel hole (1), an arch wall net-jet support structure for performing primary support on an arch wall of the tunnel hole (1), an inverted arch primary support structure for performing primary support on the bottom of the tunnel hole (1) and an anchoring system arranged on the outer side of the full-section support structure; the full-section supporting structure comprises a plurality of full-section supporting frames which are arranged from back to front along the longitudinal extension direction of the tunnel, the two adjacent full-section supporting frames at the front and the back are fixedly connected into a whole through a plurality of longitudinal connecting reinforcing steel bars, the longitudinal connecting reinforcing steel bars are horizontally arranged and arranged along the longitudinal extension direction of the tunnel, and the plurality of longitudinal connecting reinforcing steel bars are arranged along the contour line of the full-section supporting frames; the shape of the full-section support frame is the same as the shape of the cross section of the tunnel hole (1), each full-section support frame is formed by splicing an arch wall support arch frame for supporting an arch wall of the tunnel hole (1) and a tunnel inverted arch support frame (2) for supporting the bottom of the tunnel hole (1), the tunnel inverted arch support frame (2) is positioned under the arch wall support arch frame and positioned on the same tunnel cross section, and the tunnel inverted arch support frame (2) and the arch wall support arch frame form a closed full-section support;
the arch wall mesh-spraying supporting structure and the arch wall steel arch frame in the full-section supporting structure form an arch wall primary supporting structure (12), and the inverted arch primary supporting structure and the tunnel inverted arch bracket (2) in the full-section supporting structure form a primary supporting inverted arch (13); the inverted arch primary support structure is an inverted arch concrete injection layer (20) injected at the bottom of a tunnel hole (1), and the tunnel inverted arch support (2) is fixed in the inverted arch concrete injection layer (20);
the arch wall supporting arch center consists of an upper arch center (2-1) positioned in an upper hole body (1-1), two middle side brackets (5) symmetrically arranged below the left side and the right side of the upper arch center (2-1) and positioned in a middle hole body (1-2), and two lower side brackets (6) symmetrically arranged below the left side and the right side of the upper arch center (2-1) and positioned in a lower hole body (1-3), wherein the tunnel arch support (2) is positioned in the lower hole body (1-3); each middle side bracket (5) is connected between the upper end of one lower side bracket (6) and the upper arch frame (2-1); the left end of the tunnel inverted arch support (2) is fixedly connected with the bottom of one lower side support (6), and the right end of the tunnel inverted arch support (2) is fixedly connected with the bottom of the other lower side support (6);
the anchoring system comprises a plurality of anchoring groups which are arranged from back to front along the longitudinal extension direction of the tunnel, one anchoring group is uniformly distributed on the outer side of each full-section supporting frame, and each full-section supporting frame and the anchoring group arranged on the full-section supporting frame are arranged on the same cross section of the tunnel (1);
each anchoring group comprises a left group of upper locking leg anchor pipes (8), a right group of middle locking leg anchor pipes (9) and a left group of lower locking leg anchor pipes (10), wherein the left group of upper locking leg anchor pipes and the right group of lower locking leg anchor pipes are symmetrically arranged at the outer sides of the bottoms of the left side and the right side of an upper arch frame (2-1), the left group of middle locking leg anchor pipes and the right group of lower locking leg anchor pipes are symmetrically arranged, and the two groups of upper locking leg anchor pipes (8), the two groups of middle locking leg anchor pipes (9) and the two groups of lower locking leg anchor pipes (10) are uniformly; a group of middle locking leg anchor pipes (9) is arranged on the outer side of the bottom of each middle side support (5), and a group of lower locking leg anchor pipes (10) is arranged on the outer side of the bottom of each lower side support (6); each group of upper locking leg anchor pipes (8) comprises an upper locking leg anchor pipe (8) and a lower locking leg anchor pipe (8) which are arranged in parallel, each group of middle locking leg anchor pipes (9) comprises an upper middle locking leg anchor pipe (9) and a lower middle locking leg anchor pipe (9) which are arranged in parallel, and each group of lower locking leg anchor pipes (10) comprises an upper lower locking leg anchor pipe (10) which are arranged in parallel; the upper foot locking anchor pipe (8), the middle foot locking anchor pipe (9) and the lower foot locking anchor pipe (10) are all foot locking anchor pipes which enter the soil layer on the periphery of the tunnel cave (1) from inside to outside and are gradually inclined downwards from inside to outside;
when the second lining construction is carried out in the third step, when the tunnel secondary lining is constructed from back to front, the inverted arch secondary lining (15) is constructed on the constructed primary support inverted arch (13) from back to front, and the inverted arch secondary lining (15) formed by construction is obtained; in the process of constructing the inverted arch secondary lining (15) from back to front, constructing the arch wall secondary lining (14) on the constructed inverted arch secondary lining (15) from back to front, and connecting the constructed arch wall secondary lining (14) and the inverted arch secondary lining (15) positioned below the constructed arch wall secondary lining into a whole to obtain the constructed tunnel secondary lining;
in the step, in the construction process of the inverted arch secondary lining (15) from back to front, after concrete poured in the inverted arch secondary lining (15) is finally solidified, the inverted arch secondary lining (15) and a primary support inverted arch (13) form the tunnel inverted arch structure formed by construction.
10. The construction method of the shallow tunnel in the loess gully according to claim 9, wherein: and step two, when tunnel excavation and primary support are carried out, the method comprises the following steps:
step B1, excavating an upper cavity and performing primary support: excavating an upper hole body (1-1) of the constructed loess tunnel from back to front along the longitudinal extension direction of the tunnel;
in the excavation process of the upper cavity body (1-1), performing net-spraying support on the arch part of the excavated and molded upper cavity body (1-1) from back to front, and simultaneously installing an upper arch frame (2-1) in the excavated and molded upper cavity body (1-1) from back to front to finish the excavation and primary support construction process of the upper cavity body (1-1);
step B2, excavating a middle cavity and performing primary support: b1, excavating the middle hole body (1-2) below the excavated and molded upper hole body (1-1) from back to front along the longitudinal extension direction of the tunnel in the process of excavating the upper hole body and primary supporting;
in the middle hole body (1-2) excavation process, respectively carrying out net-spraying support on the left side and the right side of the middle hole body (1-2) which is formed by excavation from back to front, and simultaneously respectively installing middle side brackets (5) on the left side and the right side of the middle hole body (1-2) which is formed by excavation from back to front, and enabling each middle side bracket (5) to be fixedly connected with the upper arch centering (2-1) in the step B1 into a whole, so that the middle hole body (1-2) excavation and primary support construction processes are completed;
in the step, the excavation surface of the middle hole body (1-2) is positioned behind the excavation surface of the upper hole body (1-1), and the horizontal distance between the excavation surfaces is 4-6 m;
step B3, excavating a lower cavity and performing primary support: b2, excavating the lower hole body (1-3) below the excavated and molded middle hole body (1-2) from back to front along the longitudinal extension direction of the tunnel in the process of excavating the middle hole body and primary supporting;
in the process of excavating the lower hole body (1-3), respectively carrying out net-spraying support on the left side and the right side of the excavated and molded lower hole body (1-3) from back to front, and respectively installing lower side brackets (6) on the left side and the right side of the excavated and molded lower hole body (1-3) from back to front synchronously in the process of net-spraying support, so that each lower side bracket (6) is fixedly connected with the middle side bracket (5) in the step B2 into a whole; meanwhile, a tunnel inverted arch support (2) is arranged at the bottom of the lower hole body (1-3) from back to front, and the arranged tunnel inverted arch support (2) is fixedly connected with lower side supports (6) arranged at the left side and the right side of the lower hole body (1-3) into a whole; in the installation process of the tunnel inverted arch support (2), synchronously spraying a layer of concrete from back to front at the bottom of the tunnel hole (1) to form an inverted arch concrete spraying layer (20), and fixing the tunnel inverted arch support (2) in the inverted arch concrete spraying layer (20) to finish the excavation and primary support construction process of the lower hole body (1-3);
in the step, the excavation surface of the lower cavity body (1-3) is positioned behind the excavation surface of the middle cavity body (1-2), and the horizontal distance between the excavation surfaces is 4-6 m;
in the step, the tunnel cave (1) formed by excavation is obtained in the process of excavating the lower cave body (1-3) from back to front; respectively carrying out net-spray supporting on the left side and the right side of the lower hole body (1-3) which is formed by excavation from back to front to obtain the constructed and formed arch wall net-spray supporting structure; the arch wall net spraying support structure is connected with an inverted arch concrete spraying layer (20).
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