Lining structure suitable for stratum rich in fractured hydraulic rock and construction method thereof
Technical Field
The invention belongs to the technical field of tunnel engineering support, and particularly relates to a lining structure suitable for a stratum rich in fractured hydraulic rock and a construction method thereof.
Background
At present, the tunnel engineering support system in China mainly comprises a composite lining, namely a primary support system (mainly referred to as a non-woven fabric and a blind pipe), a waterproof board and a secondary lining. Under hard rock formation conditions, the primary support is typically the primary load bearing structure. In general, a composite lining tunnel supporting system allows primary support water seepage and the primary support water seepage condition is unavoidable, for the water seepage, a drainage system of a composite lining tunnel is mainly relied on to smoothly discharge the water seepage outside a secondary lining, and the water seepage through the primary support is prevented from entering the tunnel through the secondary lining by paving a waterproof board, under the condition, due to the existence of the drainage system, the water pressure acting on the secondary lining is small, so that the surface of the tunnel is guaranteed to be in a water-free state. Thus, the secondary liner is often used as a safety reserve.
Relatively speaking, the defects of the composite lining support system mainly comprise four aspects: firstly, the second lining is used as a safety reserve, so that the engineering economy is required to be improved; secondly, the working procedures are more, which is not beneficial to rapid construction; thirdly, the waterproof board divides the primary support and the secondary lining, and the integral stress of the tunnel structure is weakened; fourthly, when the tunnel leaks water, the damaged water outlet position of the waterproof board cannot be accurately found, and the treatment difficulty is high.
The single-layer lining is mainly applied to the water-free hard rock stratum at present, because the waterproof board is eliminated, the waterproof lining is realized by utilizing the spray coating or the self-waterproof structure, and the defects of the composite lining can be avoided. For water-bearing fractured hard rock formations, particularly water-rich fractured hard rock formations, the use of single-layer lining still presents a challenge in that: in the water-rich fracture hard rock stratum, because fracture water has certain water head pressure, the sprayed concrete layer cannot form high strength instantaneously and cannot bear the water pressure, and further the fracture water can form a drainage channel in the sprayed concrete layer, if a single-layer lining is adopted, water leakage or concrete block dropping phenomenon can occur, and therefore the single-layer lining is limited to be used in the water-rich fracture hard rock stratum.
Disclosure of Invention
Aiming at the problems that the underground water head is high and the stratum is rich in fractured hydraulic rock, the invention provides a single-layer lining structure and a construction method for combining advanced water drainage and depressurization holes, radial water drainage holes and concave-convex water drainage strips, which widens the application range and conditions of the single-layer lining and can avoid the problems of structural damage and water leakage of the single-layer lining in the stratum with the fractured hydraulic rock.
The invention adopts a structure formed by an advanced drainage depressurization pipe, a permeable concrete layer, a radial water discharge hole, a concave-convex drainage belt and a self-waterproof concrete layer as a tunnel lining structure, and has the remarkable characteristics compared with the conventional single-layer lining structure: through the combined measures, the surface of the surrounding rock excavated by the tunnel can be in a low water head, little water or no water state, so that the problem that the single-layer lining sprayed concrete cannot form stable strength under the condition of open water or pressure water head under the condition of water-rich crack surrounding rock is successfully avoided and solved. Specifically, the advanced water drainage and depressurization holes are utilized to drain and depressurize the hard rock stratum with the water-rich cracks in advance, so that the water head of the cracks on the excavation surface of the surrounding rock is greatly reduced, the water seepage quantity of the cracks is greatly reduced, and the bonding and stable strength formation of the first sprayed concrete layer and the surrounding structure are facilitated; then under the continuous action of the advanced water discharge pressure reducing hole, the radial water discharge hole and the concave-convex water discharge belt are utilized to form a ground water discharge channel, so that the effective bonding of the follow-up sprayed concrete and the early-stage sprayed concrete is effectively protected, and the strength of the sprayed concrete layer can be stably formed on the premise that no leakage occurs; after the single-layer lining strength reaches the design strength, grouting is carried out on the crack surrounding rock through the advanced water discharge hole, part of surrounding rock cracks are plugged, the water seepage quantity of the surrounding rock is reduced, the groundwater environment is guaranteed, the water pressure possibly born by the lining is reduced, even if the water pressure acting on the lining is increased due to the abnormality of the drainage system during operation, the lining structure can bear the water pressure due to the design strength value, and the structural safety can be ensured. The method can effectively improve the integrity and the safety of the single-layer lining structure, can avoid the problem of water leakage of the structure, and has the characteristics of simple construction process, material saving, low construction cost, environmental protection and the like.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: the lining structure suitable for the stratum rich in the fractured hydraulic rock comprises a self-waterproof concrete layer, wherein a concave-convex drainage belt, non-woven fabrics and a permeable concrete layer are arranged between the self-waterproof concrete layer and surrounding rock, the concave-convex drainage belt is circumferentially arranged on the outer side of the self-waterproof concrete layer and is longitudinally arranged at intervals along a tunnel, the non-woven fabrics are covered on the outer side of the concave-convex drainage belt, the outer side surface of the permeable concrete layer is covered on the inner wall of the surrounding rock, and the inner side surface of the permeable concrete layer is contacted with the non-woven fabrics or the self-waterproof concrete layer;
an advanced drainage depressurization pipe and a radial drainage pipe are arranged on the permeable concrete layer at intervals, one end of the advanced drainage depressurization pipe penetrates through the self-waterproof concrete layer and the permeable concrete layer, and the other end of the advanced drainage depressurization pipe extends to 5-10 m in surrounding rock along the longitudinal direction of the tunnel by 10-15 degrees, preferably to 6.5-7 m; one end of the radial drain pipe is abutted with the non-woven fabric, and the other end of the radial drain pipe vertically penetrates through the permeable concrete layer in the circumferential direction and extends to 20-80 cm in the surrounding rock, and preferably extends for 30-40 cm;
and drainage holes are formed in the bottom of the self-waterproof concrete layer and at positions corresponding to the concave-convex drainage bands.
Furthermore, the advanced drainage depressurization pipe is a pipe wrapped by a 40-60 mesh filter screen, and water permeable holes are formed in the pipe.
Further, the radial drain pipe is a pipe wrapped by the reverse filtering layer, and water permeable holes are formed in the pipe.
Further, the width of the concave-convex water draining belt is 20-30cm, and the width of the non-woven fabric is 2-3 cm wider than the two sides of the concave-convex water draining belt.
Furthermore, the inner side surface of the self-waterproof concrete layer is provided with a protection beautifying layer.
Furthermore, the advanced drainage depressurization pipes and the radial drainage pipes are alternately arranged in the circumferential direction, the circumferential spacing is 0.5-0.75m, the circumferential spacing of the advanced drainage depressurization pipes is 1-1.5 m, and the circumferential spacing of the radial drainage pipes is 1-1.5 m.
Furthermore, the longitudinal distance between the radial drain pipes is 2.5-3.0m, and an advanced drainage depressurization pipe, preferably 2 pipes, are arranged in the middle of each 2-3 radial drain pipes.
The invention also provides a construction method of the lining structure suitable for the stratum rich in the fractured hydraulic rock, which comprises the following steps:
s1, excavating a tunnel profile surface and removing unstable rock;
s2, spraying the permeable concrete with the thickness of 3-5 cm on the profile surface of the tunnel by adopting a wet spraying process, wherein the compressive strength of the permeable concrete can reach 3Mpa after spraying for 2 hours so as to form the permeable concrete layer;
s3, punching an advanced drainage depressurization hole and a radial drainage hole in the permeable concrete layer, and respectively inserting the advanced drainage depressurization pipe and the radial drainage pipe;
s4, covering non-woven fabrics on the radial drain holes, and fixing the non-woven fabrics with the permeable concrete layer; a concave-convex water draining belt is fixedly arranged on the inner side of the non-woven fabric, and a water draining hole is preset at the bottom of the concave-convex water draining belt correspondingly;
s5, paving a reinforcing mesh, and then spraying self-waterproof concrete with the waterproof grade being more than P20 and 0.6-0.8% of steel fibers for multiple times, wherein the thickness of the self-waterproof concrete is 25-30cm, so as to form the self-waterproof concrete layer;
s6, grouting the fracture surrounding rock by using the advanced drainage depressurization pipe, wherein the slurry adopts superfine cement slurry, and the grouting pressure is 0.2-0.4 MPa; the method for grouting the fracture surrounding rock by using the advanced drainage depressurization pipe can be as follows: the reserved advanced drainage depressurization pipe is directly used for grouting, the reserved advanced drainage depressurization pipe can be reserved beside the advanced drainage depressurization pipe in advance, and the grouting pipe can be directly inserted into the advanced drainage depressurization pipe for grouting.
S7, cutting off the part, extending out of the waterproof concrete layer, of the advanced drainage depressurization pipe, and plugging to enable the surface of the waterproof concrete layer to be flat, and further covering by using a protection beautifying layer in the later period;
s8, arranging a protection beautifying layer on the inner side surface of the self-waterproof concrete layer.
In step S2, the pervious concrete is slag cement, and the cement-cement ratio of slag cement is 0.45-0.55.
In step S5, the thickness of the self-waterproof concrete sprayed each time is about 80-120mm, and the time interval of each spraying is not more than 2 hours.
The beneficial effects of the invention are as follows:
(1) After the tunnel profile surface is excavated, a layer of concrete with early strength, good water permeability and thickness of 3-5 cm is sprayed in time, so that surrounding rock is prevented from falling down, and construction safety is guaranteed.
(2) Aiming at the condition that single-layer lining shotcrete cannot form stable strength under the condition of open water or pressure water head, advanced water drainage and depressurization holes are formed, water drainage and depressurization are carried out on a water-rich fracture hard rock stratum in advance, the water head of fracture water on the excavation surface of surrounding rock is greatly reduced, the water seepage quantity of the fracture is greatly reduced, and the first-layer shotcrete is bonded with the surrounding structure and the strength is formed stably.
(3) The permeable sprayed concrete layer, the radial water discharge holes and the concave-convex water discharge holes are combined to form the surrounding rock water seepage drainage guide channel, and the surrounding rock seepage guide channel is combined with the advanced water discharge and pressure reduction holes, so that the surface of the surrounding rock excavated by the tunnel is in a state of little water or no water, the stability of the strength formed by the sprayed concrete of the second layer is ensured, the sprayed concrete layer is effectively bonded with the sprayed concrete layer of the first layer, and the problem that the sprayed concrete cannot form strength instantaneously under the condition of bright water is effectively avoided. Even if the water pressure on the lining is increased due to the blocking condition of the drainage system in the later period, the structure safety can be ensured and the water leakage phenomenon can not occur because the sprayed concrete reaches the design strength and has the self-waterproof function.
(4) The method can effectively improve the integrity and safety of the single-layer lining structure, widens the application range and conditions of the single-layer lining, can avoid the problem of water leakage of the structure, and has the characteristics of simple construction process, material saving, low engineering cost, environmental protection and the like.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is an enlarged schematic view of FIG. 1 at A;
FIG. 3 is a layout of a relief drain belt;
FIG. 4 is an axial cross-sectional view of a tunnel;
FIG. 5 is a schematic view of groundwater flow; arrows in the figure indicate groundwater flow direction;
FIG. 6 is a practical case of a conventional single layer lining for a fracture-enriched hydraulic rock formation;
FIG. 7 is a graph of water permeability between a conventional single-lined self-waterproof concrete layer and surrounding rock;
FIG. 8 is a graph of water permeability between a self-waterproofing concrete layer and surrounding rock according to the present invention;
FIG. 9 is a practical representation of the single layer lining of the present invention for use in a fracture-enriched hydraulic rock formation;
the reference numerals in the figures are: 1-surrounding rock, 2-advanced drainage depressurization pipe, 3-radial drainage pipe, 4-permeable concrete layer, 5-non-woven fabric, 6-concave-convex drainage belt, 7-self-waterproof concrete layer, 8-protection beautifying layer and 9-drainage hole.
Detailed Description
The technical solution of the present invention will be described in further detail with reference to the accompanying drawings, but the scope of the present invention is not limited to the following description.
Example 1
Referring to fig. 1-5, the invention provides a lining structure suitable for a stratum rich in fractured hydraulic rock, which comprises a self-waterproof concrete layer 7, wherein a concave-convex drainage belt 6, non-woven fabrics 5 and a permeable concrete layer 4 are arranged between the self-waterproof concrete layer 7 and surrounding rock 1, the concave-convex drainage belt 6 is circumferentially arranged outside the self-waterproof concrete layer 7 and longitudinally arranged at intervals along a tunnel, the non-woven fabrics 5 are covered above the concave-convex drainage belt 6, the outer side surface of the permeable concrete layer 4 is covered on the inner wall of the surrounding rock 1, and the inner side surface is contacted with the non-woven fabrics 5 or the self-waterproof concrete layer 7;
the permeable concrete layer 4 is provided with an advanced drainage depressurization pipe 2 and a radial drainage pipe 3 at intervals, one end of the advanced drainage depressurization pipe 2 penetrates through the self-waterproof concrete layer 7 and the permeable concrete layer 4, and the other end of the advanced drainage depressurization pipe extends to 5-10 m in the surrounding rock 1 along the longitudinal direction of the tunnel by 10-15 degrees; one end of the radial drain pipe 3 is abutted against the non-woven fabric 5, and the other end of the radial drain pipe vertically penetrates through the permeable concrete layer 4 in the circumferential direction and extends into the surrounding rock 1 for 20-80 cm;
and a drain hole 9 is formed at the bottom of the waterproof concrete layer 7 and at the position corresponding to the concave-convex drain belt 6.
Example 2
On the basis of the embodiment 1, referring to fig. 1-5, the water permeable pipe is a pipe wrapped by a filter screen, and water permeable holes are formed in the pipe. Preferably, the permeable pipe is a PVC pipe wrapped by a 40-60 mesh filter screen, plum blossom-shaped permeable holes with the diameter of 3-4 mm are arranged on the PVC pipe, the distance between the permeable holes is 2-3 mm, and the filter screen is used for preventing soil particles from entering the pipe and preventing the permeable pipe from being blocked during construction.
The radial drain pipe 3 is a pipe wrapped by a reverse filtering layer, and water permeable holes are formed in the pipe. Preferably, the radial drain pipe 3 is wrapped with a counter-filter layerThe PVC pipe is provided with plum blossom-shaped water permeable holes with the diameter of 3-4 mm, and the distance between the water permeable holes is 2-3 mm. The reverse filtering layer is used for preventing soil particles from entering the pipe and avoiding blocking the radial drain pipe in the operation period.
The width of the concave-convex water drainage belt 6 is 20-30cm, preferably 30cm, the width of the water drainage belt can be properly adjusted according to the water-rich range of surrounding rocks, and the width of the non-woven fabric 5 is 2-3 cm wider than the two sides of the concave-convex water drainage belt 6.
The inner side surface of the self-waterproof concrete layer 7 is provided with a protection beautifying layer 8.
Example 3
On the basis of the embodiment 1 or 2, referring to fig. 1 to 5, the leading-drain depressurization pipe 2 and the radial drain pipe 3 are alternately arranged circumferentially with a circumferential spacing of 0.5 to 0.75m. The number of the leading drain depressurization pipe 2 and the radial drain pipe 3 are substantially identical.
The longitudinal distance between the radial drain pipes 3 is 2.5-3.0m, and an advanced drainage depressurization pipe 2 is arranged between every 2-3 radial drain pipes 3. The specific value of the longitudinal distance of the radial drain pipes 3 is determined according to 1/2 of the longitudinal distance 2B of the advanced drain pressure reducing pipes 2, namely 2 radial drain pipes 3 are arranged between two adjacent advanced drain pressure reducing pipes 2, the longitudinal distance between the radial drain pipes 3 and the advanced drain pressure reducing pipes 2 is B/2, the radial drain pipes 3 and the advanced drain pressure reducing pipes 2 are arranged in a staggered mode along the circumferential direction, and the corresponding calculation formula is as follows:
advanced drainage depressurization hole length
Center-to-center spacing of concave-convex drainage belt
In the formula, each cycle excavates into a scale B (m), the length L (m) of the advanced drainage depressurization hole is usually considered according to 3m in the hard rock stratum, and the drainage depressurization Kong Waicha angle α (°), concave-convex drainage belt center distance A (m)
Example 4
1-3, referring to FIGS. 1-5, a method of constructing a lining structure suitable for use in a fracture-enriched hydraulic rock formation, comprising the steps of:
s1, excavating a tunnel profile surface and removing unstable rock according to a conventional method; the method comprises the following steps: and excavating the contour surface of the tunnel by adopting a smooth blasting technology. The peripheral eyes are arranged along the excavation contour line during blasting, the distance E between the peripheral eyes is 40-50 cm, the minimum resistance line W is controlled according to E/W=0.9-1.0, and the blasting footage is controlled within 2.5-3.0m in each cycle. The deflection angle of the peripheral eyes is not more than 2 degrees, the deflection angles of other eyes are not more than 3 degrees, the eyes are kept parallel to each other and perpendicular to the working surface as much as possible, the eyeground is kept on the same plane as much as possible, and the front-back difference is not more than 1cm. And after the main body of the excavation is blasted, the charges in the smooth blastholes are blasted simultaneously. After the tunnel profile surface is excavated, equipment such as an excavator and the like is adopted to sequentially remove unstable rocks on the surface of the surrounding rock from top to bottom.
S2, immediately spraying pervious concrete with the thickness of 3-5 cm on the contour surface of the tunnel by adopting a wet spraying process after the cleaning is finished, wherein the compressive strength of the pervious concrete can reach 3Mpa after spraying for 2 hours so as to form a pervious concrete layer 4; the permeable concrete is slag cement with larger bleeding property and larger bleeding property, and the water-cement ratio of the slag cement is 0.45-0.55 so as to enhance the permeability of the first layer of sprayed concrete.
S3, drilling advanced drainage depressurization holes and radial drainage holes on the permeable concrete layer 4 at the upper part (comprising an arch part and a side wall) of the tunnel along the circumferential direction, and respectively inserting the advanced drainage depressurization pipe 2 and the radial drainage pipe 3. When the water content in the advanced drainage depressurization pipe 2 is large, blind pipes can be paved on the wall surface to the basement, and water seepage is directly led into the ditch in the hole. The exposed length of the radial drain pipe 3 is flush with the permeable concrete layer 4 or slightly longer than 1-2 mm.
S4, covering the non-woven fabric 5 on the radial drain holes, and fixing the non-woven fabric 5 and the permeable concrete layer 4, wherein the non-woven fabric 5 is preferably fixed on the permeable concrete layer 4 by a nail gun; the inner side of the non-woven fabric 5 is fixedly provided with a concave-convex water drainage belt 6, and a nail gun is preferably adopted to fix the water-proof plate on the permeable concrete layer 4.
Furthermore, a drain hole 9 is preset at the bottom of the corresponding concave-convex drain belt 6, and the method for presetting the drain hole 9 is preferably as follows: a section of PVC drain pipe is inserted between the non-woven fabric 5 and the concave-convex drain belt 6 at the bottom of the concave-convex drain belt 6, water permeable holes are formed in the insertion part of the drain pipe, the water permeable holes are plum blossom-shaped water permeable holes with the diameter of 3-4 mm, the hole spacing is 2-3 mm, a right-angle adapter is connected to one end of the drain pipe extending out, and underground water is smoothly discharged to the ditches at two sides outside the lining after the concave-convex drain plate, so that a drain channel is formed.
S5, layingThen spraying the self-waterproof concrete with the waterproof grade being more than P20 and the steel fiber added with 0.6 to 0.8 percent for a plurality of times, wherein the thickness of the self-waterproof concrete is 25 cm to 30cm so as to form a self-waterproof concrete layer 7; the thickness of the self-waterproof concrete sprayed each time is about 80-120mm, preferably about 100mm, and the time interval of each spraying is not more than 2 hours until the self-waterproof concrete is sprayed to the designed thickness.
S6, grouting the crack surrounding rock by using a reserved grouting pipe (an advanced drainage depressurization pipe 2) after the self-waterproof concrete layer 7 reaches the design strength, wherein the grouting pressure is 0.2-0.4 MPa, so that part of surrounding rock cracks are plugged, and the water seepage quantity of the surrounding rock is reduced. At this time, the single-layer lining can bear hydraulic load and cannot leak. And entering the next circulation of excavation supporting construction.
S7, cutting off the part of the advanced drainage depressurization pipe 2 extending out of the waterproof concrete layer 7, and plugging;
s8, the protective beautifying layer 8 can be selectively sprayed on the surface of the self-waterproof concrete layer 7, so that on one hand, the lining is isolated from the external environment, the carbonization effect of the lining concrete is reduced, the structural durability is improved, and on the other hand, the surface of the lining is smooth, fine and attractive. The spraying material can be selected from anti-cracking mortar, silane and other materials with high plasticity and good ductility, the anti-cracking mortar can be considered according to the thickness of 3-5mm, and the silane layer can be considered according to the thickness of 200-300g/m 2 Consider.
Experimental example 1
The traditional single-layer lining and construction method, and the lining structure and construction method of the invention are applied to the stratum rich in the fractured hydraulic rock. The actual photographs are respectively shown in fig. 6 and 9, primary branch water leakage can be seen in fig. 6a, dome-shaped strand-shaped and drop-shaped water leakage can be seen in fig. 6b, water leakage near the arch frame can be seen in fig. 6c, water pressure can be seen in fig. 6d, and the water pressure causes block dropping, and no obvious water leakage exists in the positions of fig. 9 corresponding to the present invention.
The water seepage pressure measured on the conventional single-layer lining and the lining structure of the invention is shown in figures 7 and 8 respectively, and the water seepage pressure of the lining structure of the invention is obviously smaller, which shows that the invention has the effect of reducing the water seepage pressure between the self-waterproof concrete layer and the surrounding rock.
The foregoing is merely a preferred embodiment of the invention, and it is to be understood that the invention is not limited to the form disclosed herein but is not to be construed as excluding other embodiments, but is capable of numerous other combinations, modifications and environments and is capable of modifications within the scope of the inventive concept, either as taught or as a matter of routine skill or knowledge in the relevant art. And that modifications and variations which do not depart from the spirit and scope of the invention are intended to be within the scope of the appended claims.