Lining structure suitable for fractured water-rich hard rock stratum 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 fractured water-rich hard rock stratum and a construction method thereof.
Background
At present, the tunnel engineering support system in China mainly adopts composite lining, namely the support system is composed of a primary support system, a drainage system (mainly comprising non-woven fabrics and blind pipes), a waterproof plate and a secondary lining. Under hard rock formation conditions, the primary support is typically the primary load-bearing structure. Generally speaking, the composite lining tunnel supporting system allows primary water seepage and inevitably causes the primary water seepage, for the water seepage, the composite lining tunnel is smoothly discharged outside the secondary lining by mainly depending on the drainage and guide system of the composite lining tunnel, and a waterproof board is paved to prevent the water seepage of the primary lining from penetrating the secondary lining to enter the tunnel, under the condition, because of the existence of the drainage and guide system, the water pressure acting on the secondary lining is very small, thereby ensuring that the surface of the tunnel is in a water-free state. Therefore, the two liners often serve as safety reserves.
Relatively speaking, the composite lining support system has the following main disadvantages: firstly, the second lining is used as a safe reserve, and the engineering economy needs to be improved; secondly, the process is more, which is not beneficial to quick construction; thirdly, the waterproof board divides the primary support and the secondary lining, and the whole stress of the tunnel structure can be weakened; fourthly, when water leakage occurs in the tunnel, the damaged water outlet position of the waterproof plate cannot be accurately found, and the difficulty in remediation is high.
The single-layer lining is mainly applied to the anhydrous hard rock stratum at present because a waterproof plate is omitted and a spraying layer or a structure is used for self-waterproofing to realize the waterproofing of the lining, so that the defects of the composite lining can be avoided. For water-bearing fractured hard rock formations, particularly water-rich fractured hard rock formations, the application of single-layer lining still has a difficult problem, namely: in the water-rich fractured hard rock stratum, because the fractured water has certain water head pressure, the sprayed concrete layer cannot instantaneously form higher strength and cannot bear the water pressure, and further, the fractured water can form a drainage channel in the sprayed concrete layer, so that if a single-layer lining is adopted, the phenomenon of water leakage or concrete block falling can occur, and the single-layer lining is limited to be used in the water-rich fractured hard rock stratum.
Disclosure of Invention
Aiming at the difficult problem, the invention provides a single-layer lining structure and a construction method for combining an advanced water drainage pressure reducing hole, a radial water drainage hole and a concave-convex drainage belt, aiming at a stratum with higher underground water head and rich fractured hard rock, so that the application range and conditions of the single-layer lining are widened, and the problems of structural damage and water leakage of the single-layer lining in the water-rich fractured hard rock stratum can be avoided.
The invention adopts a structure formed by the advanced drainage pressure reducing pipe, the pervious concrete layer, the radial water outlet, the concave-convex drainage belt and the self-waterproof concrete layer as the tunnel lining structure, and has the remarkable characteristics compared with the conventional single-layer lining structure: through the combined measures, the surface of the tunnel excavation surrounding rock can be in a low water head, little water or anhydrous state, and the problem that the single-layer lining sprayed concrete cannot form stable strength under the condition of open water or a pressure water head under the condition of water-rich fractured surrounding rock is successfully avoided and solved. Specifically, the water-rich fractured hard rock stratum is drained and depressurized in advance by utilizing the advanced water drainage depressurization holes, so that a surface fractured water head of wall rock excavation is greatly reduced, fracture seepage is greatly reduced, and the bonding and stable formation strength of the first sprayed concrete layer and the surrounding knots is facilitated; then, under the continuous action of the advanced water drainage pressure reducing holes, the radial water drainage holes and the concave-convex drainage belts are utilized to form an underground water drainage conduction channel, so that the effective bonding of the subsequent sprayed concrete and the early sprayed concrete is effectively protected, and the sprayed concrete layer can stably form strength on the premise of no leakage; and then, after the strength of the single-layer lining reaches the design strength, grouting the fractured surrounding rock through the advanced drainage hole, blocking partial surrounding rock fractures, reducing the water seepage amount of the surrounding rock, guaranteeing the underground water environment, and reducing the water pressure possibly borne by the lining. 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, environment protection and the like.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: the lining structure is suitable for a crack-water-rich hard rock stratum and comprises a self-waterproof concrete layer, wherein concave-convex drainage belts, non-woven fabrics and a permeable concrete layer are arranged between the self-waterproof concrete layer and a surrounding rock, the concave-convex drainage belts are annularly arranged on the outer side of the self-waterproof concrete layer and are longitudinally arranged at intervals along a tunnel, the non-woven fabrics cover the outer sides of the concave-convex drainage belts, the outer side surfaces of the permeable concrete layer cover the inner wall of the surrounding rock, and the inner side surfaces of the permeable concrete layer are in contact with the non-woven fabrics or the self-waterproof concrete layer;
the water-permeable concrete layer is provided with advanced drainage pressure reducing pipes and radial drainage pipes at intervals, one end of each advanced drainage pressure reducing pipe penetrates through the water-resistant concrete layer and the water-permeable concrete layer, and the other end of each advanced drainage pressure reducing pipe extends into the surrounding rock by 5-10 m, preferably 6.5-7 m, along the longitudinal direction of the tunnel by 10-15 degrees; one end of the radial drain pipe is abutted against the non-woven fabric, and the other end of the radial drain pipe penetrates through the pervious concrete layer in a circular direction and extends into the surrounding rock by 20-80 cm, preferably by 30-40 cm, perpendicular to the tunnel;
and drain holes are formed at the bottom of the self-waterproof concrete layer and at positions corresponding to the concave-convex drainage belts.
Furthermore, the advanced water drainage pressure reducing pipe is a pipe wrapped by a 40-60 mesh filter screen, and water permeable holes are formed in the pipe.
Furthermore, the radial water discharge pipe is a pipe wrapped by the inverted filter layer, and a water permeable hole is formed in the pipe.
Furthermore, the width of the concave-convex drainage belt is 20-30cm, and the width of the non-woven fabric is 2-3 cm wider than the width of each of two sides of the concave-convex drainage belt.
Furthermore, a protective beautifying layer is arranged on the inner side surface of the self-waterproof concrete layer.
Furthermore, the advanced drainage pressure reducing pipes and the radial drainage pipes are arranged in an annular alternating mode, the annular distance is 0.5-0.75m, the annular distance of the advanced drainage pressure reducing pipes is 1-1.5 m, and the annular distance of the radial drainage pipes is 1-1.5 m.
Furthermore, the longitudinal distance between the radial water discharge pipes is 2.5-3.0m, and an advanced water discharge and pressure reduction pipe is arranged between every 2-3 radial water discharge pipes, preferably 2 radial water discharge pipes are arranged at intervals.
The invention also provides a construction method of the lining structure suitable for the stratum rich in fractured hydraulic rocks, which comprises the following steps of:
s1, excavating a tunnel contour surface and removing unstable rocks;
s2, spraying pervious concrete with the thickness of 3-5 cm and the compressive strength of 3Mpa after spraying for 2 hours on the contour surface of the tunnel by adopting a wet spraying process to form a pervious concrete layer;
s3, drilling an advanced water drainage pressure reducing hole and a radial water drainage hole in the pervious concrete layer, and respectively inserting the advanced water drainage pressure reducing pipe and the radial water drainage pipe;
s4, covering a non-woven fabric on the radial drain hole, and fixing the non-woven fabric and the pervious concrete layer; a concave-convex drainage belt is fixedly arranged on the inner side of the non-woven fabric, and a drainage hole is preset at the bottom of the concave-convex drainage belt;
s5, laying a steel bar mesh, and then spraying self-waterproof concrete with the waterproof grade of more than P20 and added with 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 a self-waterproof concrete layer;
s6, grouting the fractured surrounding rock by using the advanced drainage depressurization pipe, wherein the grout adopts superfine cement paste, and the grouting pressure is 0.2-0.4 MPa; the method for grouting the fractured surrounding rock by using the advanced water drainage and pressure reduction pipe can be as follows: the reserved advanced drainage pressure reducing pipe is directly used for grouting, the reserved advanced drainage pressure reducing pipe can be reserved beside the advanced drainage pressure reducing pipe in advance, and a grouting pipe can be directly inserted into the advanced drainage pressure reducing pipe for grouting.
S7, cutting off the part of the advanced drainage pressure reducing pipe extending out of the waterproof concrete layer, plugging to level the surface of the waterproof concrete layer, and further covering by using a protective beautifying layer at the later stage;
and S8, arranging a protective beautifying layer on the inner side surface of the self-waterproof concrete layer.
Further, in step S2, the pervious concrete is slag cement, and the water cement ratio of the slag cement is 0.45-0.55.
Further, in step S5, the thickness of the self-waterproof concrete sprayed each time is about 80 to 120mm, and the time interval of spraying each time is not more than 2h.
The beneficial effects of the invention are:
(1) After the tunnel contour surface is excavated, the early height and the strength are achieved by timely spraying one layer, the water permeability is good, the thickness is 3-5 cm of concrete, surrounding rock falling blocks are prevented, and the construction safety is guaranteed.
(2) Aiming at the condition that the single-layer lining sprayed concrete can not form stable strength under the condition of open water or a pressure water head, the water-rich fractured hard rock stratum is drained and depressurized in advance by arranging the advanced water drainage depressurization hole, so that the surface fractured water head of the wall rock excavation is greatly reduced, the fractured water seepage amount is greatly reduced, and the bonding and stable strength forming between the first layer sprayed concrete layer and the surrounding knots are facilitated.
(3) The surrounding rock water seepage drainage channel is formed by combining the permeable sprayed concrete layer, the radial water drainage holes and the concave-convex drainage belts, and is combined with the advanced water drainage pressure reducing holes for use, so that the surface of the tunnel-excavated surrounding rock is in a low-water or anhydrous state, the second layer of sprayed concrete is guaranteed to stably form strength, and the second layer of sprayed concrete is effectively bonded with the first layer of sprayed concrete layer, and the problem that the sprayed concrete cannot instantaneously form strength under the open water condition is effectively avoided. Even the later stage because above-mentioned row leads the system to appear blockking up the condition, leads to the water pressure increase of being used in on the lining cutting, because sprayed concrete has reached design intensity and has from waterproof function, still can guarantee structure safety and the percolating water phenomenon does not appear.
(4) The method can effectively improve the integrity and safety of the single-layer lining structure, broaden the application range and conditions of the single-layer lining, avoid the problem of water leakage of the structure, and has the characteristics of simple construction process, material saving, low construction cost, environment protection and the like.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is an enlarged schematic view of FIG. 1 at A;
FIG. 3 is a view showing the arrangement of a concave-convex drainage belt;
FIG. 4 is an axial cross-sectional view of the tunnel;
FIG. 5 is a schematic view of groundwater flow; the arrows in the figure indicate groundwater flow direction;
FIG. 6 is a practical case of a conventional single-layer lining for a fractured hydraulic rock-rich formation;
FIG. 7 is a diagram of water permeability pressure between a conventional single-layer lined self-waterproofing concrete layer and surrounding rocks;
FIG. 8 is a diagram of water permeability pressure between the self-waterproofing concrete layer and the surrounding rock according to the present invention;
FIG. 9 is a practical case of a single layer lining of the present invention for a fractured hydraulic rock rich formation;
the reference numbers in the figures are: 1-surrounding rock, 2-advanced drainage pressure reducing pipe, 3-radial drainage pipe, 4-permeable concrete layer, 5-non-woven fabric, 6-concave-convex drainage belt, 7-self waterproof concrete layer, 8-protective beautifying layer and 9-drainage hole.
Detailed Description
The technical solutions of the present invention are further described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following descriptions.
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 concave-convex drainage belts 6, non-woven fabrics 5 and a permeable concrete layer 4 are arranged between the self-waterproof concrete layer 7 and a surrounding rock 1, the concave-convex drainage belts 6 are annularly arranged on the outer side of the self-waterproof concrete layer 7 and are longitudinally arranged along a tunnel at intervals, the non-woven fabrics 5 cover the concave-convex drainage belts 6, the outer side surface of the permeable concrete layer 4 covers the inner wall of the surrounding rock 1, and the inner side surface is in contact with the non-woven fabrics 5 or the self-waterproof concrete layer 7;
the pervious concrete layer 4 is provided with advanced drainage pressure reducing pipes 2 and radial drainage pipes 3 at intervals, one end of each advanced drainage pressure reducing pipe 2 penetrates through the waterproof concrete layer 7 and the pervious concrete layer 4, and the other end of each advanced drainage pressure reducing pipe extends into the surrounding rock 1 for 5-10 m 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 penetrates through the pervious concrete layer 4 in the annular direction and extends into the surrounding rock 1 by 20-80 cm;
a drain hole 9 is arranged at the bottom of the waterproof concrete layer 7 and at the position corresponding to the concave-convex drainage belt 6.
Example 2
On the basis of 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 on the pipe. Preferably, the water permeable pipe is a PVC pipe wrapped by a 40-60-mesh filter screen, plum blossom-shaped water permeable holes with the diameter of 3-4 mm are arranged on the PVC pipe, the distance between the water permeable holes is 2-3 mm, and the filter screen is used for preventing soil particles from entering the pipe and avoiding blocking the water permeable pipe during construction.
The
radial drain pipe 3 is a pipe wrapped by the inverted filter layer, and a water permeable hole is formed in the pipe. Preferably, the
radial drains 3 are filter-wrapped
The pipe and the PVC pipe are provided with quincunx water permeable holes with the diameter of 3-4 mm and between the water permeable holesThe distance is 2-3 mm. The inverted filter layer is used for preventing soil particles from entering the pipe, and the radial drain pipe is prevented from being blocked in the operation period.
The width of the concave-convex drainage belt 6 is 20-30cm, preferably 30cm, the width of the drainage belt can be properly adjusted according to the water-rich degree of the surrounding rock, and the width of the non-woven fabric 5 is 2-3 cm wider than the width of each of two sides of the concave-convex drainage belt 6.
And a protective beautifying layer 8 is arranged on the inner side surface of the waterproof concrete layer 7.
Example 3
On the basis of the embodiment 1 or 2, referring to fig. 1 to 5, the advanced water drainage and pressure reduction pipes 2 and the radial water drainage pipes 3 are arranged in an annular alternating mode, and the annular distance is 0.5 to 0.75m. The number of the advanced drainage pressure reducing pipes 2 is basically consistent with that of the radial drainage pipes 3.
The longitudinal distance between the radial water discharge pipes 3 is 2.5-3.0m, and an advanced water discharge pressure reducing pipe 2 is arranged in the middle of every 2-3 radial water discharge pipes 3. The specific longitudinal distance value of the radial drain pipes 3 is determined according to 1/2 of the longitudinal distance 2B between the advanced drainage pressure reducing pipes 2, namely 2 radial drain pipes 3 are arranged between two adjacent advanced drainage pressure reducing pipes 2, the longitudinal distance between each radial drain pipe 3 and each advanced drainage pressure reducing pipe 2 is B/2, the radial drain pipes 3 and the advanced drainage pressure reducing pipes 2 are arranged in a circular staggered mode, and the corresponding calculation formula is as follows:
length of pressure reducing hole for advanced drainage
Center distance between concave-convex drainage belts
In the formula, the length L (m) of a drainage pressure reducing hole is advanced and the external insertion angle of the drainage pressure reducing hole is advanced according to 3m in the hard rock stratum after each cycle of excavation of the scale B (m) α (°) concave-convex drainage band center distance A (m)
Example 4
On the basis of the embodiments 1-3 and referring to fig. 1-5, the construction method of the lining structure suitable for the hard rock stratum rich in fractured water comprises the following steps:
s1, excavating a tunnel contour surface and removing unstable rocks according to a conventional method; the method comprises the following specific steps: and adopting a smooth blasting technology to excavate the contour surface of the tunnel. During blasting, the peripheral holes are arranged along the excavation contour line, the distance E between the peripheral holes is 40-50 cm, the minimum resistance line W is controlled according to E/W = 0.9-1.0, and each cycle of blasting footage is controlled within 2.5-3.0 m. The deflection angles of the blastholes of the peripheral holes are not more than 2 degrees, the deflection angles of other blastholes are not more than 3 degrees, the blastholes 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 excavation main body is blasted by adopting uncoupled powder charging, the powder charging in the light blast hole is simultaneously detonated. After the excavation of the tunnel contour surface is finished, equipment such as an excavator 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 clearing is finished, wherein the compressive strength of the pervious concrete can reach 3Mpa after the pervious concrete is sprayed for 2 hours, so as to form a pervious concrete layer 4; the pervious 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 water permeability of the first layer of sprayed concrete.
And S3, drilling an advanced drainage pressure reducing hole and a radial drainage hole on the permeable concrete layer 4 at the upper part (including the arch part and the side wall) of the tunnel along the annular direction, and respectively inserting the advanced drainage pressure reducing pipe 2 and the radial drainage pipe 3. When the water amount in the advanced drainage pressure reducing pipe 2 is large, a blind pipe can be adopted to be laid to the wall foot along the wall surface, and the seepage water is directly guided into the ditch in the tunnel. The exposed length of the radial drain pipe 3 is flush with the pervious concrete layer 4 or slightly longer by 1-2 mm.
S4, covering the radial drain holes with non-woven fabrics 5, fixing the non-woven fabrics 5 and the water-permeable concrete layer 4, and preferably fixing the non-woven fabrics 5 on the water-permeable concrete layer 4 by using a nail gun; the concave-convex drainage belt 6 is fixedly arranged on the inner side of the non-woven fabric 5, and the waterproof and drainage plate is preferably fixedly arranged on the pervious concrete layer 4 by a nail gun.
Furthermore, a drain hole 9 needs to be preset at the bottom of the corresponding concave-convex drainage belt 6, and the method for presetting the drain hole 9 is preferably as follows: at 6 bottom positions in unsmooth drainage zone, insert one section PVC drain pipe between 5 and the unsmooth drainage zone of non-woven fabrics, drain pipe male portion is provided with the hole of permeating water, and the hole of permeating water is 3 ~ 4 mm's the quincunx type hole of permeating water for the diameter, and hole interval 2 ~ 3mm, one end that the drain pipe extends out has connect right angle crossover sub, smoothly arranges the outer both sides ditch of lining cutting with unsmooth drain bar back groundwater, forms drainage channel.
S5, paving
Then, the self-waterproof concrete with the waterproof grade of more than P20 and added with 0.6-0.8% of steel fibers is sprayed for multiple times, and the thickness of the self-waterproof concrete is 25-30cm, so that a self-waterproof
concrete layer 7 is formed; the thickness of the waterproof concrete is about 80-120mm, preferably about 100mm, and the time interval of each spraying is not more than 2h until the waterproof concrete is sprayed to the designed thickness.
S6, after the self-waterproof concrete layer 7 reaches the designed strength, grouting the fractured surrounding rock by using a reserved grouting pipe (the advanced drainage pressure reducing pipe 2), wherein the grouting liquid is made of superfine cement paste, the grouting pressure is 0.2-0.4 MPa, and partial surrounding rock fractures are plugged, so that the water seepage amount of the surrounding rock is reduced. At this time, the single-layer lining can bear hydraulic pressure load and cannot leak. And entering the next circulation of excavation and support construction.
S7, cutting off the part of the advanced drainage pressure reducing pipe 2 extending out of the waterproof concrete layer 7, and plugging;
s8, a protective beautifying layer 8 can be selectively sprayed on the surface of the self-waterproof concrete layer 7, so that the lining is isolated from the external environment, carbonization of the lining concrete is reduced, structural durability is improved, and the surface of the lining is smooth, fine and attractive. The spraying material can be selected from anti-crack mortar, silane and other materials with high plasticity and good ductility, the anti-crack mortar can be considered according to the thickness of 3-5mm, and the silane layer can be 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 fractured hydraulic rock. The actual photographs are respectively shown in fig. 6 and fig. 9, the water leakage of the primary support can be seen from fig. 6a, the water leakage of the arch top strand shape and the drop shape can be seen from fig. 6b, the water leakage close to the arch center can be seen from fig. 6c, the water pressure can be seen from fig. 6d to cause block dropping, and the corresponding situations of obvious water leakage and the like do not exist in all positions of fig. 9.
The water seepage pressure of the traditional single-layer lining and the lining structure of the invention is respectively measured as shown in figure 7 and figure 8, the water seepage pressure of the lining structure of the invention is obviously smaller, and the effect of reducing the water seepage pressure between the self-waterproof concrete layer and the surrounding rock is demonstrated.
The foregoing is illustrative of the preferred embodiments of the present invention, and it is to be understood that the invention is not limited to the precise form disclosed herein and is not to be construed as limited to the exclusion of other embodiments, and that various other combinations, modifications, and environments may be used and modifications may be made within the scope of the concepts described herein, either by the above teachings or the skill or knowledge of the relevant art. And that modifications and variations may be effected by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.