Double-layer outer-rigid inner-flexible composite lining drainage system and construction method thereof

Abstract

The invention provides a double-layer outer-rigid inner-flexible composite lining drainage system and a construction method thereof, and belongs to the technical field of high-water-pressure tunnel drainage type lining design and construction. The outer-layer rigid drainage system is arranged in a full-ring mode, the radial water guide blind pipes are vertically inserted into surrounding rock, the annular water guide blind pipes and the longitudinal water guide blind pipes are pre-buried in a secondary lining, the water guide blind pipes are connected through five-way connectors, and the tail ends of the annular water guide blind pipes are connected into an inverted arch center ditch. The inner-layer flexible drainage system is arranged in a semi-ring mode, the planar geotechnical cloth is located on the outer side of the annular drainage blind pipe, the annular drainage blind pipe is connected with the longitudinal water collection blind pipe through the three-way connector, the two ends of the transverse drainage blind pipe are connected with the longitudinal water collection blind pipe and the drainage side ditch respectively, and the drainage side ditch is communicated with the inverted arch center ditch through the transverse drainage blind pipe. The method has the advantages that a large amount of underground water is drained before entering the primary support, the drainage and pressure reduction effects are very obvious, the safety reserve is high, the structural durability is remarkably improved, and the service life of a tunnel is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of high water pressure tunnel drainage lining design and construction, and specifically relates to a double-layer outer-rigid and inner-flexible composite lining drainage system and a construction method thereof. Background Art

[0002] As the service time of high water pressure tunnels in water-rich strata increases, water-related diseases such as lining cracking and leakage, arch uplift, and track deformation frequently occur, endangering driving safety and operational stability. The reason is that conventional drainage systems are generally set between primary support and secondary lining. Groundwater can enter the drainage system only after passing through the primary support, and flexible drainage materials such as geotextiles, soft permeable pipes, and concave-convex drainage strips are always used. They are easy to deform and cause poor drainage or even abnormal blockage. Groundwater will accumulate behind the secondary lining, resulting in the actual external water pressure it bears is far greater than expected. The structural stress and deformation are completely inconsistent with the original design intention, which will induce water-related diseases over time.

[0003] Generally, there are four reasons for abnormal blockage of conventional drainage systems: 1) The initial support is corroded by groundwater and its permeability gradually increases, and the amount of groundwater inside the initial support exceeds the designed drainage capacity;

[0004] 2) The flexible drainage material shrinks in diameter or becomes thinner under the deformation pressure of the surrounding rock, thus weakening the effective water-passing section;

[0005] 3) The grouting effect continues to deteriorate, the initial support corrosion fails, and a large amount of foreign matter and impurities enter the drainage system, causing blockage;

[0006] 4) The invert is not equipped with drainage facilities, and the groundwater below it cannot be discharged in time, causing water damage. Even if some tunnel inverts are equipped with drainage systems, the combined effect of the deadweight of the invert, roadbed, backfill and other structures as well as the dynamic load of the vehicle will also cause the drainage system to be completely blocked and useless.

[0007] In actual projects, the above four reasons exist simultaneously and promote each other to form a vicious circle. The cost and expense of rectifying the defects during operation are unbearable and inestimable. What's worse, the operation needs to be interrupted frequently and for a long time, which is very detrimental to people's livelihood and has a huge social impact. The best proof of this is that more and more high-pressure tunnels are suffering from water diseases and are difficult to cure. Summary of the invention

[0008] The purpose of the present invention is to overcome the difficulties faced by the prior art and proposes a double-layer, outer-rigid and inner-flexible composite lining drainage system and its construction method, wherein the outer-layer rigid drainage device is the core drainage and pressure relief facility, and the inner-layer flexible drainage device is the drainage and pressure relief compensation and reserve facility. The two have different setting ranges, spatial staggered, main and auxiliary, orderly drainage, and complementary effects, and jointly solve the above-mentioned technical problems.

[0009] In order to achieve the above-mentioned object, the present invention is implemented by the following technical scheme: a double-layer outer rigid inner flexible composite lining drainage system, comprising an outer rigid drainage device and an inner flexible drainage device, wherein the outer rigid drainage device is arranged along the entire ring of the tunnel, and comprises radial water guide blind pipes, annular water guide blind pipes, longitudinal water guide blind pipes and an inverted arch central ditch, wherein the radial water guide pipe is vertically inserted into the surrounding rock, and is connected with the annular water guide blind pipe and the longitudinal water guide blind pipe through a five-way joint, wherein the annular water guide blind pipe and the longitudinal water guide blind pipe are pre-buried in the secondary lining, and the end of the annular water guide blind pipe is connected to the inverted arch central ditch;

[0010] The inner layer flexible drainage device is arranged along the tunnel semi-circle and is not set in the range of the inverted arch, including annular drainage blind pipe, longitudinal water collecting blind pipe, transverse water discharge blind pipe, waterproof isolation layer and drainage ditch. The annular drainage blind pipe is arranged in the waterproof isolation layer between the initial support and the secondary lining. The two ends of the annular drainage blind pipe are connected with the longitudinal water collecting blind pipe through a three-way joint. The two ends of the transverse water discharge blind pipe are respectively connected with the longitudinal water collecting blind pipe and the drainage ditch. The transverse drainage blind pipe is buried in the backfill layer of the inverted arch, one end of which is connected to the bottom of the drainage ditch, and the other end extends into the center ditch of the inverted arch.

[0011] Preferably, the waterproof isolation layer includes a planar geotextile and a waterproof board. The planar geotextile is laid closely to the initial support base surface, and the end of the planar geotextile is inserted into the reserved groove on the wall of the longitudinal water collection blind pipe. The waterproof board is laid closely to the outer base surface of the secondary lining, and the annular drainage blind pipe is located between the planar geotextile and the waterproof board.

[0012] Preferably, the longitudinal water collecting blind pipes are arranged longitudinally throughout, and the transverse water discharge blind pipes are arranged longitudinally at intervals and form a staggered arrangement relationship with the annular water guiding blind pipes.

[0013] Preferably, the radial water-conducting blind pipe passes through the waterproof board, the planar geotextile, and the initial support in sequence from the inside to the outside and is inserted into the surrounding rock; the radial water-conducting blind pipe wall is provided with water-permeable holes and is covered with non-woven fabric and barbs are provided at intervals; the radial water-conducting blind pipe is arranged in a circular and longitudinal bidirectional rectangular manner; the longitudinal arrangement spacing of the annular water-conducting blind pipe is equal to the longitudinal arrangement spacing of the radial water-conducting blind pipe; the circumferential arrangement spacing of the longitudinal water-conducting blind pipe is equal to the circumferential arrangement spacing of the radial water-conducting blind pipe.

[0014] Preferably, the non-woven fabric, waterproof sheet and planar geotextile are extended into the interior of the secondary lining at the radial water-guiding blind pipe position, pressed and overlapped with each other, and are fastened and sealed with metal hoops, and a water-swellable waterproofing strip is provided at the end of the metal hoop.

[0015] Preferably, the drainage path of the outer rigid drainage device is: groundwater in the surrounding rock enters the radial water blind pipe, then enters the annular water blind pipe and the longitudinal water blind pipe, and finally, flows into the central ditch of the invert through the annular water blind pipe.

[0016] Preferably, the drainage path of the inner flexible drainage device is: the groundwater that cannot be discharged by the outer rigid drainage device penetrates into the interior of the initial support, and then enters the longitudinal water collection blind pipe along the surface geotextile and the annular drainage blind pipe, and then is drained to the drainage side ditch through the transverse drainage blind pipe, and finally, is merged into the central ditch of the inverted arch through the transverse drainage blind pipe.

[0017] Preferably, the effective water-passing cross-sectional area of ​​the central ditch of the inverted arch needs to be larger than the sum of the effective water-passing cross-sectional areas of the drainage ditches on both sides to avoid flooding the roadbed due to insufficient water collection capacity.

[0018] Preferably, the effective water-passing cross-section of the central ditch of the inverted arch should be larger than the drainage ditches on both sides to avoid flooding the roadbed due to insufficient water collection capacity.

[0019] Another technical solution protected by the present invention is a construction method of a double-layer outer rigid inner flexible composite lining drainage system, which is characterized by: following the steps:

[0020] Step S1: Implement tunnel advance curtain grouting water-stopping and support reinforcement measures;

[0021] Step S2: excavate the tunnel soil and apply initial support, level the base surface after penetration, and lay the surface geotextile, annular drainage blind pipe, longitudinal water collection blind pipe, and waterproof board in sequence;

[0022] Step S3: laying radial water guide blind pipes and tying the steel reinforcement skeleton of the secondary lining water-facing surface;

[0023] Step S4: laying out the annular water guide blind pipe, the longitudinal water guide blind pipe, and the transverse water discharge blind pipe, and fixing them firmly with positioning steel bars, and connecting the blind pipes in order with pipe joints;

[0024] Step S5: Use metal hoops to waterproof the geotextile, waterproof board, and non-woven fabric, and set multiple water-swellable waterproof rubber strips at the ends;

[0025] Step S6: tying the remaining steel bar skeleton of the secondary lining and setting up the formwork, and pouring the secondary lining concrete;

[0026] Step S7: After curing to the designed strength, the formwork is removed, the transverse drainage blind pipes are arranged, the drainage side ditches and the central ditch of the invert are molded, and the invert backfill layer is applied.

[0027] Compared with the prior art, the invention has the following beneficial effects.

[0028] 1. The double-layer drainage system of the present invention has the advantages of significant drainage and pressure reduction effect, high safety reserve, and durability. It can flexibly respond to abnormal changes in the groundwater level within the project scope, especially resist the sudden rise in water level caused by rainy season, flood season, and tides, and ensure the safety of tunnel structure stress and controllable deformation.

[0029] 2. Since the water permeability of the surrounding rock is much greater than that of the initial support, a large amount of groundwater will be discharged through the outer rigid drainage device first, and only a very small amount of groundwater can enter the initial support, reducing the corrosion effect of groundwater on the initial support and secondary lining, significantly improving the durability of the composite lining, and extending the service life of the tunnel.

[0030] 3. The inner flexible drainage device of the present invention serves as a drainage pressure relief compensation and reserve facility, which can effectively eliminate the hidden dangers caused by poor drainage or abnormal blockage of the outer rigid drainage device, without having to face the drawbacks and shortcomings of the conventional drainage system caused by frequent blockages, such as lining cracks and structural leakage.

[0031] 4. By setting barbs at intervals on the wall of the radial water-guiding blind pipe, which is equivalent to an external anchor structure with multi-point support, a favorable radial outward pulling force can be provided to the secondary lining to prevent radial separation from the smooth contact interface of the initial support, significantly improve the internal force distribution of the structure, and alleviate structural deformation, especially the uplift of the invert.

[0032] 5. An outer rigid drainage device that is not affected by the deadweight of the lining, ballast, backfill and other structures and the dynamic load of the vehicle is installed under the invert, which can effectively alleviate the external water pressure on the invert and avoid water-related diseases such as ballast pumping and track deformation that seriously endanger driving safety and operational stability.

[0033] 6. The drainage ditch receives very little groundwater, which eventually flows into the central ditch of the invert. During service, the central ditch of the invert only needs normal inspection and maintenance, without interrupting operation to inspect the drainage ditch across the track, which significantly reduces the operating pressure and maintenance risk of the tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a cross-sectional view of a double-layer, outer-rigid, inner-flexible composite lining drainage system according to an embodiment of the present invention.

[0035] Figure 2 This is a node diagram of the radial water-guiding blind pipe structure of the outer rigid drainage device in an embodiment of the present invention.

[0036] Figure 3 This is a node diagram of the drainage closure structure of the inner layer flexible drainage device according to an embodiment of the present invention.

[0037] In the figure, 1 is a radial water guide blind pipe, 2 is an annular water guide blind pipe, 3 is a longitudinal water guide blind pipe, 4 is an inverted arch central ditch, 5 is a surface geotextile, 6 is annular drainage blind pipe, 7 is a longitudinal water collection blind pipe, 8 is a transverse discharge blind pipe, 9 is a drainage ditch, 10 is a transverse drainage blind pipe, 11 is an initial support, 12 is a secondary lining, 13 is a waterproof board, 14 is a non-woven fabric, 15 is a barb, 16 is a metal hoop, and 17 is a water-swellable water-stop strip. DETAILED DESCRIPTION

[0038] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and examples, so as to fully understand and implement the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects.

[0039] like Figure 1 As shown, a double-layer outer rigid and inner flexible composite lining drainage system includes an outer rigid drainage device and an inner flexible drainage device. The outer rigid drainage device is arranged along the entire ring of the tunnel, including radial water blind pipe 1, annular water blind pipe 2, longitudinal water blind pipe 3 and inverted arch central water ditch 4. The radial water blind pipe 1 is vertically inserted into the surrounding rock to a depth of 2.0m. The radial water blind pipe 1 is connected to the annular water blind pipe 2 and the longitudinal water blind pipe 3 through a five-way joint. The annular water blind pipe 2 and the longitudinal water blind pipe 3 are both pre-buried in the middle of the thickness of the secondary lining 12, and the end of the annular water blind pipe 2 extends into the side wall of the inverted arch central water ditch 4 by 50mm.

[0040] The inner layer flexible drainage device is arranged along the tunnel semi-circle and is not set in the invert range to avoid ineffectiveness. The inner layer flexible drainage device includes an annular drainage blind pipe 6, a longitudinal water collection blind pipe 7, a transverse drainage blind pipe 8, a waterproof isolation layer and a drainage ditch 9. The annular drainage blind pipe 6 is arranged in the waterproof isolation layer between the initial support 11 and the secondary lining 12. The annular drainage blind pipe 6 is connected to the longitudinal water collection blind pipe 7 through a three-way joint. The two ends of the transverse drainage blind pipe 8 are respectively connected to the longitudinal water collection blind pipe 7 and the side wall of the drainage ditch 9 and extend into the drainage ditch 50mm. The transverse drainage blind pipe 10 is buried in the backfill layer of the invert, one end of which is connected to the bottom of the drainage ditch 9, and the other end extends into the side wall of the central ditch 4 of the invert by 50mm.

[0041] The structure of the double-layer drainage system of the present invention is briefly introduced above. The drainage process of the system is introduced in detail below based on the above structure.

[0042] Since the water permeability of the surrounding rock is much greater than that of the initial support, the drainage system of the present invention uses the outer rigid drainage device as the core drainage and pressure relief facility, and the inner flexible drainage device as the drainage and pressure relief compensation and reserve facility. A large amount of groundwater in the surrounding rock enters the multiple groups of radial water blind pipes 1 scattered in the surrounding rock, and then enters the annular water blind pipe 2 and the longitudinal water blind pipe 3. Finally, the annular water blind pipe 2 is merged into the central ditch 4 of the invert. The bottom of the pipe needs to be 250mm higher than the bottom of the ditch to prevent flooding.

[0043] The groundwater that cannot be discharged by the outer rigid drainage device penetrates into the initial support 11, and then enters the longitudinal water collection blind pipe 7 along the surface geotextile 5 and the annular drainage blind pipe 6. After that, it is discharged to the drainage side ditch 9 through the transverse drainage blind pipe 8, and finally, it is collected into the central ditch 4 of the invert arch by the transverse drainage blind pipe 10. The bottom of the pipe needs to be 350mm higher than the bottom of the ditch to prevent flooding.

[0044] The present invention sets multiple groups of radial water blind pipes 1 in the outer surrounding rock part, so that a large amount of groundwater will first enter the radial water blind pipes 1, and then directly discharge into the central ditch 4 of the inverted arch through the annular water blind pipes 2 and the longitudinal water blind pipes 3 connected thereto. Only a very small amount of groundwater can enter the interior of the initial support 11, which greatly reduces the corrosion of the initial support 11 and the secondary lining 12 by groundwater, significantly improves the durability of the composite lining, and extends the service life of the tunnel. As for a small amount of groundwater that infiltrates into the interior of the initial support 11, the present invention also sets an inner flexible drainage device, which is collected by using a planar geotextile 5 and annular drainage blind pipes 6, and finally also flows into the central ditch 4 of the inverted arch. The inner flexible drainage device can effectively eliminate the hidden dangers caused by poor drainage or abnormal blockage of the outer rigid drainage device, and there is no need to face the disadvantages and shortcomings of the conventional drainage system that causes lining cracks and structural leakage due to frequent blockage.

[0045] In the above embodiment, the structure and drainage principle of the double-layer outer rigid and inner flexible composite lining drainage system of the present invention are introduced in detail, but the specific structure and arrangement of the outer rigid drainage device and the inner flexible drainage device are not specifically limited. In order for those skilled in the art to better understand the present invention, on the basis of the above embodiment, it is introduced in detail in this embodiment.

[0046] The annular drainage blind pipe 6 of the inner flexible drainage device is arranged in the middle of the waterproof isolation layer. The waterproof isolation layer includes a planar geotextile 5 and a waterproof board 13. The planar geotextile 5 is laid closely to the base surface of the initial support 11, and the end of the planar geotextile 5 is inserted into the reserved groove of the wall of the longitudinal water collection blind pipe 7. Part of the groundwater will directly seep into the longitudinal water collection blind pipe 7 through the planar geotextile 5, thereby alleviating the corrosion effect of groundwater on the initial support and the secondary lining. The waterproof board 13 is laid closely to the outer base surface of the secondary lining 12.

[0047] The annular drainage blind pipe 6 is located between the planar geotextile 5 and the waterproof board 13. The annular drainage blind pipe 6 adopts a spring skeleton soft permeable pipe, and the longitudinal arrangement spacing is 9.0m. Two longitudinal water collection blind pipes 7 are arranged longitudinally, and the transverse drainage blind pipes 8 are arranged longitudinally at intervals of 12.0m and are arranged in a staggered arrangement relationship with the annular water guide blind pipe 2 to avoid space conflict.

[0048] The radial blind water pipe 1 of the outer rigid drainage device passes through the waterproof board 13, the planar geotextile 5, and the initial support 11 from the inside to the outside, and then is inserted into the surrounding rock. The wall of the radial blind water pipe 1 is reserved with plum blossom-shaped permeable holes so that groundwater can smoothly enter the outer rigid drainage system. At the same time, the wall is covered with the non-woven fabric 14 with a thickness of 3mm and barbs 15 are set at intervals of 250mm. The non-woven fabric 14 can effectively prevent the permeable holes in the wall of the radial blind water pipe 1 from being blocked, and prevent groundwater from entering the interior of the outer rigid drainage device. The barbs 15 have a dual function. One is to prevent the radial blind water pipe 1 from moving radially, and the other is to limit the deformation of the secondary lining 12 toward the inside of the tunnel under the action of external loads.

[0049] The non-woven fabric 14, waterproof board 13 and planar geotextile 5 are extended into the secondary lining 12 at the radial water blind pipe 1, and are pressed and overlapped with each other. The length of the pressing and overlapping is not less than 200 mm, and the metal hoop 16 is used to tighten and seal the water. Part of the groundwater in the planar geotextile 5 of this design and structure can flow along the non-woven fabric 14 and directly enter the radial water blind pipe 1 through the reserved permeable holes, further reducing the amount of groundwater flowing in the inner flexible drainage device, giving full play to the drainage and pressure reduction capacity of the outer rigid drainage system. In addition, two circumferential water-swelling waterproofing strips 17 are set at the end of the metal hoop 16 to further strengthen the waterproof effect of the weak link.

[0050] The radial water blind pipe 1 is arranged in a rectangular manner of 2.5m in the circumferential direction and 3.0m in the longitudinal direction; the longitudinal arrangement spacing of the circumferential water blind pipe 2 is equal to the longitudinal arrangement spacing of the radial water blind pipe 1, which is 3.0m; the circumferential arrangement spacing of the longitudinal water blind pipe 3 is equal to the circumferential arrangement spacing of the radial water blind pipe 1, which is 2.5m. The circumferential arrangement spacing of the radial water blind pipe 1 in the invert range should be smaller than the arch wall position to facilitate the upward drainage of groundwater against gravity. The circumferential arrangement spacing of the longitudinal water blind pipe 2 in the invert range needs to be adjusted synchronously to keep it consistent.

[0051] The double-layer outer-rigid and inner-flexible composite lining drainage system of the present invention is introduced in detail in the above two embodiments. The construction method of the double-layer drainage system of the present invention is introduced in detail below with respect to the above structure.

[0052] A construction method for a double-layer outer-rigid and inner-flexible composite lining drainage system, the method comprising the following steps:

[0053] Step S1: Implement tunnel advance curtain grouting water-stopping and support reinforcement measures;

[0054] Step S2: excavate the tunnel soil and apply initial support 11, level the base surface after penetration, and lay the surface geotextile 5, the annular drainage blind pipe 6, the longitudinal water collection blind pipe 7, and the waterproof board 13 in sequence;

[0055] Step S3: laying radial water-guiding blind pipes 1 and tying the steel reinforcement skeleton of the secondary lining 12 on the water-facing surface;

[0056] Step S4: Lay out the annular water guide blind pipe 2, the longitudinal water guide blind pipe 3, and the transverse drainage blind pipe 8, and firmly fix them with positioning steel bars, and connect the blind pipes in order with suitable joints;

[0057] Step S5: Use metal hoop 16 to waterproof the geotextile 5, waterproof board 13, and non-woven fabric 14, and set two water-swellable waterproof rubber strips 17 at the ends;

[0058] Step S6: tying the remaining steel bar skeleton of the secondary lining 12 and setting up the formwork, and pouring the concrete of the secondary lining 12;

[0059] Step S7: After curing to the designed strength, the formwork is removed, the transverse drainage blind pipe 10 is arranged, the drainage side ditch 9 and the inverted arch central ditch 4 are molded, and the inverted arch backfill layer is applied.

[0060] In addition, the end of the radial water-guiding blind pipe 1 should not exceed the setting range of the curtain grouting, ensuring a safety distance of at least 1.0m to prevent a large amount of groundwater in the stratum that has not been reinforced by grouting from entering the outer drainage system, violating the limited drainage design concept and increasing the drainage burden of the outer drainage system.

[0061] It can be seen from the above technical scheme that the double-layer outer rigid and inner flexible composite lining drainage system and its construction method of the present invention use the outer rigid drainage system as the core drainage and pressure relief facility, and the inner flexible drainage system as the drainage and pressure relief compensation and reserve facility. It has the advantages of significant drainage and pressure reduction effect, reduced lining deformation and stress, reduced structural thickness and steel consumption, convenient operation and maintenance, improved driving safety environment, and extended tunnel service life, etc., and has outstanding promotion value and engineering benefits.

[0062] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A double-layer outer rigid inner flexible composite lining drainage system, characterized by: The invention comprises an outer rigid drainage device and an inner flexible drainage device. The outer rigid drainage device is arranged along the entire ring of the tunnel and comprises a radial water guide blind pipe (1), an annular water guide blind pipe (2), a longitudinal water guide blind pipe (3) and an inverted arch central water ditch (4). The radial water guide pipe (1) is vertically inserted into the surrounding rock and is connected to the annular water guide blind pipe (2) and the longitudinal water guide blind pipe (3) through a five-way joint. The annular water guide blind pipe (2) and the longitudinal water guide blind pipe (3) are pre-buried in the secondary lining (12). The end of the annular water guide blind pipe (2) is connected to the inverted arch central water ditch (4). The inner layer flexible drainage device is arranged along the tunnel semi-circle and is not provided in the inverted arch range, and comprises an annular drainage blind pipe (6), a longitudinal water collection blind pipe (7), a transverse drainage blind pipe (8) and a drainage ditch (9). The annular drainage blind pipe (6) is arranged in a waterproof isolation layer between the initial support (11) and the secondary lining (12). The two ends of the annular drainage blind pipe (6) are connected to the longitudinal water collection blind pipe (7) through a three-way joint. The two ends of the transverse drainage blind pipe (8) are respectively connected to the longitudinal water collection blind pipe (7) and the drainage ditch (9). The transverse drainage blind pipe (10) is buried in the inverted arch backfill layer, one end of which is connected to the bottom of the drainage ditch (9) and the other end extends into the center ditch (4) of the inverted arch.

2. A double-layer outer rigid inner flexible composite lining drainage system according to claim 1, characterized in that: The waterproof isolation layer comprises a planar geotextile (5) and a waterproof board (13); the planar geotextile (5) is laid in close contact with the base surface of the initial support (11); the end of the planar geotextile (5) is inserted into a reserved groove on the wall of the longitudinal water collection blind pipe (7); the waterproof board (13) is laid in close contact with the outer base surface of the secondary lining (12); and the annular drainage blind pipe (6) is located between the planar geotextile (5) and the waterproof board (13).

3. A double-layer outer rigid and inner flexible composite lining drainage system according to claim 1 or 2, characterized in that: The longitudinal water collection blind pipe (7) is arranged along the longitudinal length of the tunnel, and the transverse water discharge blind pipe (8) is arranged at intervals in the longitudinal direction and forms a staggered arrangement relationship with the annular water guide blind pipe (2).

4. The double-layer outer rigid and inner flexible composite lining drainage system according to claim 2 is characterized by: The radial water-conducting blind pipe (1) passes through the waterproof plate (13), the planar geotextile (5), and the initial support (11) from the inside to the outside in sequence and is then inserted into the surrounding rock; the radial water-conducting blind pipe (1) is provided with water-permeable small holes on its wall and is covered with a non-woven fabric (14) and barbs (15) are arranged at intervals; the radial water-conducting blind pipe (1) is arranged in a circular longitudinal bidirectional rectangular manner; the longitudinal arrangement spacing of the circular water-conducting blind pipe (2) is equal to the longitudinal arrangement spacing of the radial water-conducting blind pipe (1); the circumferential arrangement spacing of the longitudinal water-conducting blind pipe (2) is equal to the circumferential arrangement spacing of the radial water-conducting blind pipe (1).

5. A double-layer outer rigid inner flexible composite lining drainage system according to claim 4, characterized in that: The non-woven fabric (14), waterproof sheet (13) and planar geotextile (5) are extended into the interior of the secondary lining (12) at the position of the radial water-guiding blind pipe (1) to be mutually compressed and overlapped, and are fastened and sealed with a metal hoop (16). A water-swellable waterproofing strip (17) is provided at the end of the metal hoop (16).

6. The double-layer outer rigid inner flexible composite lining drainage system according to claim 1 is characterized by: The drainage path of the outer rigid drainage device is as follows: groundwater in the surrounding rock enters the radial water blind pipe (1), then enters the annular water blind pipe (2) and the longitudinal water blind pipe (3), and finally flows into the central water ditch (4) of the inverted arch through the annular water blind pipe (2).

7. The double-layer outer rigid and inner flexible composite lining drainage system according to claim 1 is characterized by: The drainage path of the inner flexible drainage device is as follows: the groundwater that cannot be drained away by the outer rigid drainage device penetrates into the interior of the initial support (11), and then enters the longitudinal water collection blind pipe (7) along the planar geotextile (5) and the annular drainage blind pipe (6), and then is drained to the drainage side ditch (9) through the transverse drainage blind pipe (8), and finally, is collected into the central ditch (4) of the inverted arch through the transverse drainage blind pipe (10).

8. The double-layer outer rigid and inner flexible composite lining drainage system according to claim 1 is characterized by: The outer walls and inner walls of the radial water-guiding blind pipe (1), the annular water-guiding blind pipe (2), and the longitudinal water-guiding blind pipe (3) are fully coated with an antiseptic.

9. The double-layer outer rigid inner flexible composite lining drainage system according to claim 1 is characterized by: The effective water-passing cross-sectional area of ​​the inverted central ditch (4) is greater than the sum of the effective water-passing cross-sectional areas of the drainage side ditches (9) on both sides.

10. A construction method for a double-layer outer rigid inner flexible composite lining drainage system, characterized in that: Follow these steps: Step S1: Implement tunnel advance curtain grouting water-stopping and support reinforcement measures; Step S2: excavating the tunnel soil and applying initial support (11), leveling the base surface after penetration, and laying the planar geotextile (5), the annular drainage blind pipe (6), the longitudinal water collection blind pipe (7), and the waterproof board (13) in sequence; Step S3: laying radial water-conducting blind pipes (1) and tying the steel reinforcement skeleton of the water-facing surface of the secondary lining (12); Step S4: laying out the annular water guide blind pipe (2), the longitudinal water guide blind pipe (3), and the transverse water discharge blind pipe (8), and fixing them firmly with positioning steel bars, and connecting the blind pipes in order with pipe joints; Step S5: Using a metal hoop (16) to waterproof the flat geotextile (5), the waterproof board (13), and the non-woven fabric (14), and providing a plurality of water-swellable waterproof rubber strips (17) at the ends; Step S6: tying the remaining steel bars of the secondary lining (12) and setting up the formwork, and pouring the secondary lining (12) concrete; Step S7: After curing to the designed strength, the formwork is removed, the transverse drainage blind pipe (10) is arranged, the drainage side ditch (9) and the central ditch of the invert (4) are molded, and the invert backfill layer is applied.

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