A seismic-resistant tough support structure and construction method for cross-fault tunnels

Abstract

This invention discloses a seismic-resistant and resilient support structure and construction method for cross-fault tunnels. The structure includes multiple combined anchor bolts, a secondary lining layer, a waterproof and vibration-damping layer 3, and a primary lining, arranged sequentially from the inside of the tunnel outwards. The primary lining, waterproof and vibration-damping layer, and secondary lining layer circumferentially surround the tunnel interior, with the layer closest to the soil layer on the outside. The primary lining is in close contact with the tunnel wall. By using combined anchor bolts and prefabricated assembled lining, damage to the tunnel structure from earthquakes and fault slippage is reduced, improving the seismic performance and post-earthquake recoverability of the tunnel support structure, and enhancing the overall seismic resilience of the tunnel.

Description

Technical Field

[0001] This invention belongs to the field of tunnel seismic resistance technology, specifically relating to a seismic-resistant tough support structure and construction method for cross-fault tunnels. Background Technology

[0002] With the increasing number of transportation tunnel construction projects, due to the limitations of terrain conditions, tunnels inevitably have to pass through earthquake-prone areas and fault fracture zones. Experience shows that earthquakes can cause fault slippage, which can lead to damage to tunnels that cross faults.

[0003] Existing tunnel seismic reinforcement technologies mostly tend to enhance the strength of existing structures, such as increasing lining thickness and grouting reinforcement. Even after adopting such reinforcement technologies, significant damage or deformation will still occur under earthquake action, and it is difficult to repair them to a usable level after the earthquake, which seriously affects the smooth flow of traffic lifelines.

[0004] In recent years, the concept of seismic resilience in buildings has been widely promoted. Seismic resilience refers to a building's ability to maintain and restore its original functions after a set level earthquake. Traditional tunnel reinforcement methods can only meet seismic safety requirements, exhibiting poor post-earthquake recoverability. Therefore, enhancing the seismic resilience of tunnels spanning fault lines has become a crucial issue urgently needing to be addressed in tunnel engineering construction. Summary of the Invention

[0005] The purpose of this invention is to provide a seismic toughness support structure and construction method for cross-fault tunnels. By using combined anchor bolts and prefabricated assembled linings, the damage to the tunnel structure caused by earthquakes and fault slippage is reduced, the seismic performance and post-earthquake recoverability of the tunnel support structure are improved, and the overall seismic toughness of the tunnel is enhanced.

[0006] The present invention adopts the following technical solution: a combined anchor bolt, comprising an anchor cable and an anchor bolt body arranged in the same axial direction, the anchor cable and the anchor bolt body being connected by a steel strand connector (15);

[0007] The steel strand connector includes an anchor bolt sleeve, an anchor cable sleeve, and a clamp. The anchor bolt sleeve is a cylindrical tube with open ends. Its rear end is threaded to the front end of the anchor bolt body. Its front end is connected to the anchor cable sleeve by a double-ended bolt.

[0008] The anchor cable sleeve is a shell structure with open ends. The front end is a cone-shaped cavity with the tip pointing forward, and the rear end is a cylindrical cavity.

[0009] A clamp is installed inside the conical cavity. The clamp is a frustum with its small end facing forward. A through hole is opened along the central axis of the frustum. An anchor cable is axially connected inside the through hole. When the rock and soil deform, the clamp moves forward, the anchor cable grows, and the bearing capacity of the deep surrounding rock is mobilized.

[0010] Furthermore, the anchor cable has a tapered head axially connected to its front end; the rear end of the anchor rod is threadedly connected to an anchor head nut, and an anchor plate is coaxially sleeved on the anchor rod in front of the anchor head nut.

[0011] The cone head is located at the bottom of the borehole, which is located in deep surrounding rock. The anchor rod passes through the primary lining and is connected to it. The anchor plate at the rear end is attached to the tunnel wall and is fixed by screwing on the anchor head nut.

[0012] Furthermore, multiple grouting holes are arranged on the rear section of the anchor rod body. The rear end of the anchor rod body is used to connect with the grouting device. Grout is injected through the rear end of the anchor rod body, and the grout overflows from the multiple grouting holes and seeps into the rock and soil.

[0013] Furthermore, the front section of the anchor rod is coaxially fitted with multiple grout-stopping brushes spaced at intervals; each grout-stopping brush includes a connecting sleeve and a fixing sleeve coaxially fitted together, wherein the fixing sleeve is on the outside; the connecting sleeve is coaxially fitted on the outside of the anchor rod; the grout-stopping brush is used to prevent the grout from entering the anchor cable section at the rear end.

[0014] Each anti-grouting brush also includes a protective plate, multiple layers of steel wire, and a pressing plate stacked sequentially from the outside to the inside. The protective plate, pressing plate, and multiple layers of steel wire are all shell structures, and the rear section is an outwardly flared funnel shape. They are all coaxially sleeved outside the connecting sleeve, and the front section is located inside the fixed sleeve, while the outwardly flared funnel section is located outside the fixed sleeve; the section closest to the connecting sleeve is considered the inside.

[0015] Under the force of the slurry, the clamping plate bends backward, with its end extending towards the inner wall of the borehole and adhering to the inner wall of the borehole to block the slurry.

[0016] Furthermore, multiple fixing holes are provided on the side wall of the fixed cylinder at intervals around its circumference. Multiple connecting holes are provided on the protective plate, the pressure plate, and the multi-layer steel wire layer at positions corresponding to the fixing holes. The fixing holes and connecting holes at the same position form a group of holes. Fixing bolts are fitted into each group of holes to fix the pressure plate, the multi-layer steel wire layer, and the protective plate to the fixed cylinder.

[0017] This invention also discloses a seismic-resistant and resilient support structure for cross-fault tunnels, comprising multiple of the aforementioned combined anchor bolts, and further comprising a secondary lining layer, a waterproof and shock-absorbing layer, and a primary lining arranged sequentially from the inside of the tunnel outwards, wherein the primary lining, the waterproof and shock-absorbing layer, and the secondary lining layer circumferentially surround the inside of the tunnel, wherein:

[0018] The secondary lining layer includes a longitudinally bonded integral secondary lining and a multi-ring segmented assembled secondary lining. The integral secondary lining is used in areas outside the fault fracture zone, while the multi-ring segmented assembled secondary lining is used in the fault fracture zone.

[0019] The segmented prefabricated secondary linings of the multi-ring structure are sequentially bonded together in the longitudinal direction. Each ring of the segmented prefabricated secondary lining includes multiple prefabricated concrete segments and multiple shear rubber segments. The prefabricated concrete segments and shear rubber segments are spaced apart, and adjacent prefabricated concrete segments and shear rubber segments are bonded together.

[0020] Each of the prefabricated concrete segments includes an inverted arch block, which is U-shaped and has different heights on the left and right sides. Based on the inverted arch block, a side wall block B and an arch waist block B are connected sequentially on its left or right side, and a side wall block A and an arch waist block A are connected sequentially on its right or left side. A capping block is connected between the arch waist block B and the arch waist block A.

[0021] Furthermore, in two adjacent prefabricated concrete sections, the left and right arms of the inverted arch block are arranged in opposite directions, and the capping block, arch waist B block, side wall B block, arch waist A block and side wall A block are arranged in opposite directions to the left and right. The capping block is located to the left or right of the tunnel design centerline so that when the prefabricated concrete section is assembled, the joints between the corresponding blocks are not on the same longitudinal line.

[0022] Furthermore, each shear rubber segment is annular, consistent with the shape of its adjacent precast concrete segment; each shear rubber segment comprises, in its longitudinal direction, layers of polytetrafluoroethylene rubber sheets and thin steel sheets stacked together.

[0023] This invention also discloses a construction method for the above-mentioned seismic toughness support structure for cross-fault tunnels, comprising the following steps:

[0024] Step S1: Excavate the tunnel chamber and drill holes in the tunnel wall. There are multiple holes, and the bottom of each hole is located in the deep surrounding rock. Insert a combined anchor rod into each hole, with the cone head located at the bottom of the hole. Each grout stop brush is placed in the shallow surrounding rock section close to the deep surrounding rock in the hole. The anchor plate is attached to the surface of the rock and soil in the tunnel, and the combined anchor rod is fixed by tightening the anchor head nut.

[0025] Grouting is performed from the rear end of the anchor rod. The grout overflows from the grouting hole and seeps into the soil and rock. At the same time, any grout that does not seep in in time flows to the grout-stopping brush. Under the action of the grout, the clamping plate bends backward, and its end is attached to the borehole wall. The grout overflowing between the end of the clamping plate and the borehole wall is blocked by multiple layers of steel wire. Meanwhile, the protective plate supports the multiple layers of steel wire. The grout overflowing from the previous grout-stopping brush is blocked by the adjacent grout-stopping brush in turn.

[0026] Step S2: Install steel arch frames and steel mesh close to the excavated tunnel wall, and spray concrete after molding to form the primary lining; the rear end of the anchor rod is fixedly connected to the primary lining.

[0027] Step S3: Install a waterproof and shock-absorbing layer on the inner surface of the initial lining;

[0028] Step S4: Install a ring of segmented prefabricated secondary lining in the fault fracture zone area. Install an inverted arch block at the bottom of the tunnel, with its left arm higher and its right arm lower. Using the inverted arch block as a reference, connect the sidewall B block and the arch waist B block in sequence on its left side, and connect the sidewall A block and the arch waist A block in sequence on its right side. The arch waist B block on the left side and the arch waist A block on the right side are connected by a capping block. The capping block is located on the right side of the tunnel design centerline, completing the installation of the ring of prefabricated concrete segment. Install the shear rubber segment on the segmented prefabricated secondary lining.

[0029] Adhesive shear rubber segments are attached to adjacent ring-shaped prefabricated secondary linings. An inverted arch block is installed at the bottom of the tunnel, with its left arm lower than its right arm. Using the inverted arch block as a reference, sidewall A and arch waist A are sequentially connected to its left side, and sidewall B and arch waist B are sequentially connected to its right side. Arch waist B and arch waist A are connected by a capping block, located to the left of the tunnel's design centerline, completing the installation of one ring of prefabricated concrete segments. The shear rubber segments are then attached to the prefabricated secondary linings.

[0030] Repeat the above installation until the installation of the segmented prefabricated secondary lining in the fault fracture zone is completed;

[0031] Step S5: Inside the tunnel, in an area outside the fault fracture zone, an integral secondary lining is constructed, with one end of the integral secondary lining attached to the shear rubber segment at the end of the fault fracture zone.

[0032] The beneficial effects of this invention are as follows: 1. The anchor rod body of the combined anchor rod can be grouted to reinforce the shallow surrounding rock of the tunnel, while one end of the anchor cable is located in the structurally stable deep surrounding rock. When the shallow surrounding rock deforms, the anchor cable can mobilize the bearing capacity of the deep surrounding rock, thus leveraging the advantages of both anchor rod and anchor cable support, resulting in a stronger anchoring effect. 2. Segmented prefabricated secondary lining is used within the fault fracture zone and a 30m radius. The secondary lining is divided into segments, with a shear rubber segment between each two prefabricated concrete segments. This enhances the overall shear resistance of the segmented prefabricated secondary lining, preventing fault slippage caused by earthquakes that could damage the tunnel. Furthermore, the post-earthquake recovery cost of the segmented prefabricated secondary lining is low, and the repair work is simple, requiring only the replacement of earthquake-damaged and non-functional segments and shear rubber segments. 3. A waterproof and shock-absorbing layer is used instead of traditional geotextile and waterproofing membrane to absorb earthquake energy. Simultaneously, it sways with the raised ribs under earthquake action, dissipating earthquake energy. After an earthquake, the waterproof and shock-absorbing layer has a certain recovery capacity, improving the overall seismic toughness of the tunnel structure. Attached Figure Description

[0033] Figure 1 This is a structural schematic diagram of a seismic-resistant and tough support structure for a cross-fault tunnel.

[0034] Figure 2 This is a schematic diagram of a combined anchor bolt.

[0035] Figure 3 This is a schematic diagram of the structure of a steel strand connector;

[0036] Figure 4 Cross-sectional view of the grout brush;

[0037] Figure 5 This is a cross-sectional view of a seismic-resistant tough support structure for a cross-fault tunnel.

[0038] Figure 6 This is a schematic diagram of the seismic toughness support structure for a cross-fault tunnel.

[0039] Figure 7 Schematic diagram of segmented prefabricated secondary lining Figure 1 ;

[0040] Figure 8 Schematic diagram of segmented prefabricated secondary lining Figure 2 ;

[0041] Figure 9 Schematic diagram of waterproof and shock-absorbing partition;

[0042] The components include: 1. Anchoring system; 11. Anchor head nut; 12. Anchor plate; 13. Anchor rod body; 14. Grout stop brush; 141. Connecting sleeve; 142. Protective plate; 143. Steel wire layer; 144. Pressure plate; 145. Fixing bolt; 146. Fixing sleeve; 15. Steel strand connector; 151. Anchor sleeve; 152. Double-ended bolt; 153. Anchor cable sleeve; 154. Clamp;

[0043] 16. Anchor cable; 17. Cone head; 2. Primary lining; 3. Waterproof and shock-absorbing layer; 31. Waterproof membrane; 32. High-damping rubber layer; 33. Geotextile; 4. Secondary lining; 41. Integrated secondary lining; 42. Segmented prefabricated secondary lining; 421. Prefabricated concrete section; 4211. Capping block; 4212. Arch waist A block; 4213. Arch waist B block; 4214. Side wall A block; 4215. Side wall B block; 4216. Inverted arch block; 422. Shear rubber section; 5. Fault fracture zone. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0045] This invention discloses a combined anchor bolt, such as Figure 1 As shown, it includes anchor cables 16 and anchor rods 13 arranged one after the other along the same axis, and the anchor cables 16 and anchor rods 13 are axially connected by steel strand connectors 15.

[0046] like Figure 2As shown, the steel strand connector 15 includes an anchor bolt sleeve 151, an anchor cable sleeve 153, and a clamp 154. The anchor bolt sleeve 151 is a cylinder with open ends. Internal threads are provided on the inner walls of both the front and rear ends of the cylinder. Its rear end is threadedly connected to the front end of the anchor bolt body 13. Its front end is connected to the anchor cable sleeve 153 via a double-ended bolt 152. External threads are provided on the outer walls of both the front and rear ends of the double-ended bolt 152. The double-ended bolt 152 is threadedly connected to the anchor bolt body 13 and the anchor cable sleeve 153.

[0047] The anchor sleeve 153 is a shell structure with open ends at both the front and rear. Its interior includes, from front to back, a connected conical cavity, a large cylindrical cavity, and a small cylindrical cavity. The inner wall of the small cylindrical cavity is provided with internal threads.

[0048] The pointed end of the conical cavity faces forward and is connected to the outside. A clamp 154 ​​is installed in the connecting cavity between the conical cavity and the large cylindrical cavity. The clamp 154 ​​is a frustum, smaller than the connecting cavity. The smaller end of the frustum faces forward, and a through hole is opened along the central axis of the frustum. An anchor cable 16 is fitted into the through hole. When the rock and soil deform, the clamp 154 ​​moves forward, the anchor cable 16 grows, and the rock and soil are supported by the reverse force of the anchor cable 16. At the same time, the bearing capacity of the deep surrounding rock is mobilized, enhancing the support effect.

[0049] An axial cone head 17 is axially connected to the front end of the anchor cable 16; the anchor rod body 13 is a hollow round tube with a closed front end and an open rear end, and its rear end is provided with external threads for threaded connection with the anchor head nut 11. Multiple grout-stopping brushes 14 are coaxially sleeved on the front section of the anchor rod body 13, with the brushes spaced apart. Each brush is welded and fixed to the anchor rod body 13. An anchor plate 11 is coaxially sleeved on the anchor rod body 13, located in front of the anchor head nut 11.

[0050] The cone head 17 is located at the bottom of the borehole, which is located in the deep surrounding rock. The anchor rod 13 passes through the primary lining 2 and is connected to the primary lining 2. The anchor plate 12 at the rear end is attached to the tunnel wall and is fixed by screwing on the anchor head nut 11.

[0051] like Figure 3 As shown, multiple grouting holes are arranged on the anchor rod body 13, behind the grout-stop brush 14 at the rear end. The rear end of the anchor rod body 13 is used to connect to the grouting device. Grout is injected through the rear end of the anchor rod body 13, and the grout overflows from the multiple grouting holes and seeps into the rock and soil. The grout-stop brush 14 is used to prevent the grout from entering the anchor cable 16 section at the rear end.

[0052] Each grout-stopping brush 14 includes a connecting sleeve 141 and a fixing sleeve 146 coaxially sleeved together. The fixing sleeve 146 is on the outside, with its front end closed and its rear end open, and the length of its rear end is shorter than the length of the connecting sleeve 141. Both the front and rear ends of the connecting sleeve 141 are open. The connecting sleeve 141 is coaxially sleeved on the outside of the anchor rod body 13.

[0053] The protective plate 142, the clamping plate 144, and the multi-layer steel wire layer 143 are all shell structures. From front to back, each includes an axially connected cylindrical section and an outwardly expanding flared section. The cylindrical section is coaxially sleeved outside the connecting sleeve 141, and the cylindrical section is located inside the fixed cylinder 146, while the outwardly expanding flared section is located outside the fixed cylinder. Taking the area closest to the connecting sleeve 141 as the inside, the clamping plate 144, the multi-layer steel wire layer 143, and the protective plate 142 are arranged sequentially from the inside to the outside. On the side wall of the fixed cylinder 146, multiple fixing holes are provided at intervals around its circumference. On the protective plate 142, the clamping plate 144, and the multi-layer steel wire layer 143, multiple connecting holes are provided at positions corresponding to the fixing holes. The fixing holes and connecting holes at the same position form a group of holes, and fixing bolts 145 are fitted into each group of holes to fix the clamping plate 144, the multi-layer steel wire layer 143, and the protective plate 142 to the fixed cylinder 146. The multi-layer steel wire layer 143 consists of multiple stacked steel wire layers. The angle between the outward expansion section and the connecting sleeve 141 is 55°.

[0054] The connecting sleeve 141 is made of 5mm thick stainless steel; the protective plate 142 is made of 2mm thick stainless steel plate; the clamping plate 144 is made of 3mm thick high manganese wear-resistant steel plate; the multi-layer steel wire layer 143 includes 3 layers of 15mm thick individual steel wire layers.

[0055] Under the force of the grout, the outwardly expanding section of the clamping plate 144 bends backward, with its end extending towards the inner wall of the borehole and adhering to the inner wall to block the grout. Grout overflowing from the end of the clamping plate 144 and the borehole wall is blocked by multiple layers of steel wire 143, while the protective plate 142 supports the multiple layers of steel wire 143; grout overflowing from the previous grout-stopping brush 14 is blocked by the adjacent grout-stopping brush 14 in sequence.

[0056] This invention discloses a seismic toughness support structure for cross-fault tunnels, which is suitable for enhancing the support work of cross-fault tunnels in earthquake-prone areas and improving the seismic toughness of tunnels.

[0057] A seismic-resistant and tough support structure for cross-fault tunnels, such as Figure 4-6 As shown, it includes multiple of the above-mentioned combined anchor bolts, and also includes a secondary lining layer 4, a waterproof and shock-absorbing layer 3, and a primary lining 2 arranged sequentially from the inside of the tunnel to the outside. The primary lining 2, the waterproof and shock-absorbing layer 3, and the secondary lining layer 4 are arranged around the inside of the tunnel, with the layer closest to the rock and soil layer being the outside. The primary lining 2 is in close contact with the tunnel wall.

[0058] The anchor cable 16 of each combination anchor is inserted into the rock and soil, the cone head 17 is located at the bottom of the borehole, and the bottom of the borehole is located in the deep surrounding rock; the end of the anchor cable 16 passes through the primary lining 2 and is connected to the primary lining 2, and the anchor plate 12 at the rear end is attached to the surface of the rock and soil in the tunnel and is fixed by screwing on the anchor head nut 11.

[0059] The secondary lining layer 4 includes an integral secondary lining 41 and a multi-ring segmented assembled secondary lining 42. The integral secondary lining 41 is used in areas outside the fault fracture zone. The integral secondary lining 41 is constructed in segments, and multiple connecting holes are provided circumferentially at intervals on the end sidewall of the integral secondary lining 41.

[0060] The multi-ring segmented prefabricated secondary lining 42 is used in the fault fracture zone area, which is the area within 30m of the fault fracture zone. The multi-ring segmented prefabricated secondary lining 42 is arranged sequentially in the longitudinal direction. When the segmented prefabricated secondary lining 42 is connected to the integral secondary lining 41, a shear rubber section 422 is provided between the segmented prefabricated secondary lining 42 and the integral secondary lining 41. The fault fracture zone area and the area outside the fault fracture zone area are connected to form the entire working area.

[0061] like Figure 7 and 8 As shown, both the prefabricated concrete section 421 and the shear rubber section 422 are annular and conform to the shape of the tunnel circumference, and are used to fit the inner wall and bottom of the tunnel.

[0062] Each prefabricated concrete segment 421 includes an inverted arch block 4216, which is U-shaped with different heights on the left and right sides. Using the inverted arch block 4216 as a reference, its left or right side is sequentially connected to sidewall block B 4215 and arch waist block B 4213, while its right or left side is sequentially connected to sidewall block A 4214 and arch waist block A 4212. A capping block 4211 connects arch waist block B 4213 and arch waist block A 4212. This forms a ring that encircles the tunnel.

[0063] The capping block 4211, arch waist block B 4213, sidewall block B 4215, arch waist block A 4212, and sidewall block A 4214 are all arc-shaped, matching the curvature of the tunnel opening at their respective locations. The invert block 4216 is arc-shaped, conforming to the design dimensions. All the capping blocks 4211, arch waist block B 4213, sidewall block B 4215, arch waist block A 4212, sidewall block A 4214, and invert block 4216 are equipped with connecting holes. Joints are formed between adjacent blocks, and each joint is sealed with a penetrating crystalline coating.

[0064] In two adjacent prefabricated concrete sections 421, the left and right arms of the invert block 4216 are arranged in opposite directions. The capping block 4211, arch waist block B 4213, side wall block B 4215, arch waist block A 4212, and side wall block A 4214 are arranged in opposite directions to the left and right. The capping block 4211 is located to the left or right of the tunnel design centerline so that the joints between the corresponding blocks are not on the same longitudinal line when assembling into prefabricated concrete sections 421. The left or right arm of the invert block 4216 is flush with the structural design baseline, and the other end is 2-3m higher than the structural design baseline. The inner arc lengths of the capping block 4211, arch waist block A 4212, arch waist block B 4213, side wall block A 4214, and side wall block B 4215 are S1, S2, S3, S4, and S5, respectively, and the arc length ratio is S1:S2:S3:S4:S5 = 1:2:2:2.5:2.5. The structural design baseline is given during the tunnel design. The capping block 4211, arch waist block B 4213, sidewall block B 4215, arch waist block A 4212, sidewall block A 4214 and invert block 4216 are prefabricated outside the tunnel and transported into the tunnel.

[0065] Because the arch bears the greatest pressure, the size of the capping block 4211 is the smallest among all the blocks, so it cannot be located in a position that spans the arch. At the same time, it must also ensure that the joints between adjacent blocks are not at the arch.

[0066] Each prefabricated concrete section 421 has an impermeability grade of S10 and a concrete strength grade of C50. The length of each ring along the tunnel length direction is 1.5m. The thickness of the prefabricated concrete section 421 is the same as the thickness of the integrated secondary lining, and the curvature of each block matches the curvature of the integrated secondary lining.

[0067] Each shear rubber segment 422 is annular, consistent in shape with its adjacent prefabricated concrete segment 421. Each shear rubber segment 422 comprises, in its longitudinal direction, layers of stacked polytetrafluoroethylene (PTFE) rubber sheets and thin steel plates. The PTFE rubber sheet layer consists of multiple PTFE rubber sheets stacked sequentially in the longitudinal direction; the thin steel plate layer consists of multiple thin steel plates stacked sequentially in the longitudinal direction. Each PTFE rubber sheet has a longitudinal thickness of 5 mm; each thin steel plate has a longitudinal thickness of 5 mm. Multiple PTFE rubber sheets and thin steel plates are interlocked, bonded, and vulcanized to form a 30 mm thick shear rubber layer 422. The shear rubber segments 422 are prefabricated outside the tunnel and transported inside the tunnel when installation is required.

[0068] Multiple through holes are provided on the side wall of the sheared rubber section 422 and around its circumference. The positions of the multiple through holes correspond to the positions of the connecting holes on each block. The through holes and connecting holes at the same position are connected by bent bolt holes.

[0069] like Figure 9As shown, the waterproof and shock-absorbing layer 3 consists of geotextile 33, rubber layer 32, and waterproof membrane 31 stacked sequentially. The rubber layer is made of silicone rubber incorporating nano-silica. Rubber layer 32 includes a base plate, and the damping factor of the rubber layer material is not less than 0.4. The base plate is provided with raised ribs and grooves, with multiple raised ribs spaced apart and grooves at each interval. The direction of each raised rib is consistent with the width direction of the base plate. The thickness of the base plate is 5cm to 8cm, and the thickness of the raised ribs is 3cm to 5cm. By replacing traditional geotextile and waterproof membrane with a waterproof and shock-absorbing layer, the high-damping rubber absorbs seismic energy. Simultaneously, the raised ribs sway under seismic action, dissipating seismic energy. After an earthquake, the waterproof and shock-absorbing layer has a certain recovery capacity, improving the overall seismic toughness of the tunnel structure.

[0070] This invention also discloses a construction method for the above-mentioned seismic toughness support structure for cross-fault tunnels, comprising the following steps:

[0071] Step S1: Excavate the tunnel chamber and drill multiple holes in the tunnel wall, with the bottom of each hole located in the deep surrounding rock. Insert two sets of cement cartridges into each hole and push them to the bottom with a steel chisel. Insert a combined anchor rod 1 into each hole, with the cone head 17 located at the bottom of the hole. Insert the grout stop brush 14 into the shallow surrounding rock section near the deep surrounding rock in each hole. The anchor plate 12 is attached to the surface of the rock and soil inside the tunnel, and the anchor head nut 11 is tightened to fix the combined anchor rod 1.

[0072] Grouting is performed at the rear end of the anchor rod 13. The grout overflows from the grouting hole and seeps into the soil and rock. At the same time, the grout that does not seep in in time flows to the grout stop brush 14. Under the action of the grout, the clamping plate 144 bends backward and its end is attached to the borehole wall. The grout overflowing between the end of the clamping plate 144 and the borehole wall is blocked by the multi-layer steel wire layer 143. At the same time, the protective plate 142 supports the multi-layer steel wire layer 143. The grout overflowing from the previous grout stop brush 14 is blocked by the adjacent grout stop brush 14 in turn.

[0073] Step S2: Install steel arch frame and steel mesh close to the excavated tunnel wall, spray concrete after forming to form primary lining 2; the rear end of anchor rod 13 is fixedly connected to primary lining 2.

[0074] Step S3: Install the waterproof and shock-absorbing layer 3 on the inner surface of the initial lining 2;

[0075] Step S4: Install a ring of prefabricated secondary lining 42 in the fault fracture zone area. Install an inverted arch block 4216 at the bottom of the tunnel, with its left arm higher and its right arm lower. Using the inverted arch block 4216 as a reference, connect the sidewall B block 4215 and the arch waist B block 4213 to its left side in sequence, and connect the sidewall A block 4214 and the arch waist A block 4212 to its right side in sequence. The arch waist B block 4213 on the left side and the arch waist A block 4212 on the right side are connected by a capping block 4211. The capping block 4211 is located on the right side of the tunnel design centerline, completing the installation of the ring of prefabricated concrete section 421. Install the shear rubber section 422 on the prefabricated secondary lining 42.

[0076] Install adjacent ring segmented prefabricated secondary lining 42 by attaching shear rubber segment 422 to the already installed shear rubber segment 422. Install inverted arch block 4216 at the bottom of the tunnel, with its left arm lower and right arm higher. Using inverted arch block 4216 as a reference, connect sidewall A block 4214 and arch waist A block 4212 in sequence on its left side, and connect sidewall B block 4215 and arch waist B block 4213 in sequence on its right side. Arch waist B block 4213 and arch waist A block 4212 are connected by capping block 4211. Capping block 4211 is located to the left of the tunnel design centerline, completing the installation of one ring of prefabricated concrete segment 421. Install shear rubber segment 422 by attaching it to segmented prefabricated secondary lining 42.

[0077] Repeat the above installation until the installation of the segmented prefabricated secondary lining 42 in the fault fracture zone area is completed;

[0078] Step S5: Inside the tunnel, in an area outside the fault fracture zone, an integral secondary lining 41 is constructed, with one end of the integral secondary lining 41 attached to the shear rubber segment 422 at the end of the fault fracture zone area.

[0079] This invention discloses a seismic-resistant toughness support structure and construction method for cross-fault tunnels. It employs a combined anchor bolt system, which allows for grouting reinforcement of the shallow surrounding rock, while the anchor cable system can utilize the bearing capacity of the deeper surrounding rock, thus combining the advantages of both anchor bolt and anchor cable support for a stronger anchoring effect. Furthermore, segmented prefabricated secondary lining is used within the fault fracture zone and a 30m radius thereafter. Shear rubber sections 422 are installed between adjacent prefabricated concrete sections 421, enhancing the overall shear resistance of the secondary lining and preventing fault slippage caused by earthquakes that could damage the tunnel.

Claims

1. A composite anchor bolt, characterized in that, Includes anchor cables (16) and anchor rods (13) arranged in the same axial direction, which are connected by steel strand connectors (15); The steel strand connector (15) includes an anchor sleeve (151), an anchor cable sleeve (153) and a clamp (154). The anchor sleeve (151) is a cylinder with open ends at both ends, and its rear end is threaded to the front end of the anchor rod body (13). Its front end is connected to the anchor cable sleeve (153) by a double-headed bolt (152); The anchor sleeve (153) is a shell structure with open ends at both the front and rear. Its front end is a cone cavity with the tip pointing forward, and its rear end is a cylindrical cavity. A clamp (154) is provided in the conical cavity. The clamp (154) is a frustum with its small end facing forward. A through hole is provided along the central axis of the frustum. An anchor cable (16) is axially connected in the through hole. When the rock and soil deform, the clamp (154) moves forward and the anchor cable (16) grows, thereby mobilizing the bearing capacity of the deep surrounding rock. The front end of the anchor cable (16) is axially connected to a cone head (17); the rear end of the anchor rod body (13) is threadedly connected to an anchor head nut (11), and an anchor pad (12) is coaxially sleeved on the anchor rod body (13) in front of the anchor head nut (11). The cone (17) is located at the bottom of the borehole, and the bottom of the borehole is located in the deep surrounding rock; the anchor rod (13) passes through the primary lining (2) and is connected to the primary lining (2); the anchor plate (12) at the rear end is attached to the tunnel wall and is fixed by the anchor nut (11); Multiple grouting holes are provided on the rear section of the anchor rod body (13). The rear end of the anchor rod body (13) is used to connect with the grouting device. Grouting is performed through the rear end of the anchor rod body (13), and the grout overflows from the multiple grouting holes and seeps into the rock and soil. The front section of the anchor rod body (13) is coaxially fitted with a plurality of grout-stopping brushes (14) spaced apart front and rear; each grout-stopping brush (14) includes a connecting sleeve (141) and a fixing sleeve (146) coaxially fitted together, wherein the fixing sleeve (146) is on the outside; the connecting sleeve (141) is coaxially fitted on the outside of the anchor rod body (13); the grout-stopping brush (14) is used to prevent the grout from entering the anchor cable (16) section at the rear end; Each of the aforementioned anti-grouting brushes (14) further includes a protective plate (142), a multi-layer steel wire layer (143), and a pressing plate (144) stacked sequentially from the outside to the inside. The protective plate (142), the pressing plate (144), and the multi-layer steel wire layer (143) are all shell structures, and the rear section is an outwardly flared trumpet shape. They are all coaxially sleeved outside the connecting sleeve (141), and the front section is located inside the fixed cylinder (146). The outwardly flared trumpet section is located outside the fixed cylinder (146); with the section closest to the connecting sleeve (141) being the inside. Under the force of the slurry, the clamping plate (144) bends backward, with its end extending toward the inner wall of the borehole and adhering to the inner wall of the borehole to block the slurry.

2. A combined anchor bolt as described in claim 1, characterized in that, On the side wall of the fixed cylinder (146), a plurality of fixing holes are provided at intervals around it. On the protective plate (142), the pressing plate (144) and the multi-layer steel wire layer (143), a plurality of connecting holes are provided at positions corresponding to the fixing holes. The fixing holes and connecting holes at the same position form a group of holes. Fixing bolts (145) are fitted in each group of holes to fix the pressing plate (144), the multi-layer steel wire layer (143) and the protective plate (142) to the fixed cylinder (146).

3. A seismic-resistant and resilient support structure for cross-fault tunnels, characterized in that, The composite anchor bolt, comprising any one of claims 1-2, further comprises a secondary lining layer (4), a waterproof and shock-absorbing layer (3), and a primary lining (2) arranged sequentially from the inside of the tunnel outwards, wherein the primary lining (2), the waterproof and shock-absorbing layer (3), and the secondary lining layer (4) circumferentially surround the inside of the tunnel, wherein: The secondary lining layer (4) includes an integral secondary lining (41) and a multi-ring segmented assembled secondary lining (42) that are longitudinally bonded together. The integral secondary lining (41) is used to be installed in the area outside the fault fracture zone, and the multi-ring segmented assembled secondary lining (42) is used to be installed in the fault fracture zone. The segmented prefabricated secondary lining (42) of the multi-ring is sequentially attached in the longitudinal direction. Each segmented prefabricated secondary lining (42) of the ring includes multiple prefabricated concrete segments (421) and multiple shear rubber segments (422). The prefabricated concrete segments (421) and shear rubber segments (422) are spaced apart, and adjacent prefabricated concrete segments (421) and shear rubber segments (422) are attached and connected. Each of the prefabricated concrete segments (421) includes an inverted arch block (4216), which is U-shaped and has different heights on the left and right arms. Based on the inverted arch block (4216), the left or right side is connected to the side wall block B (4215) and the arch waist block B (4213), and the right or left side is connected to the side wall block A (4214) and the arch waist block A (4212). The arch waist block B (4213) and the arch waist block A (4212) are connected to the capping block (4211).

4. The seismic toughness support structure for cross-fault tunnels as described in claim 3, characterized in that, In two adjacent prefabricated concrete sections (421), the left and right arms of the inverted arch block (4216) are arranged in opposite directions. The capping block (4211), arch waist block B (4213), side wall block B (4215), arch waist block A (4212) and side wall block A (4214) are arranged in opposite directions to the left and right. The capping block (4211) is located to the left or right of the tunnel design centerline so that when the prefabricated concrete section (421) is assembled, the joints between the corresponding blocks are not on the same longitudinal line.

5. The seismic toughness support structure for cross-fault tunnels as described in claim 4, characterized in that, Each of the shear rubber segments (422) is annular and has the same shape as the adjacent precast concrete segment (421); each of the shear rubber segments (422) includes, in its longitudinal direction, layers of polytetrafluoroethylene rubber sheets and thin steel sheets stacked together.

6. A construction method for a seismic-resistant tough support structure for a cross-fault tunnel as described in claim 3, 4, or 5, characterized in that, Includes the following steps: Step S1: Excavate the tunnel chamber and drill holes in the tunnel wall. There are multiple holes, and the bottom of each hole is located in the deep surrounding rock. Insert a combined anchor rod (1) into each hole. The cone head (17) is located at the bottom of the hole, and each grout stop brush (14) is located in the shallow surrounding rock section close to the deep surrounding rock inside the hole. The anchor plate (12) is attached to the tunnel wall inside the tunnel, and the anchor head nut (11) is screwed on to fix the combined anchor rod (1). Grout is injected from the rear end of the anchor rod (13), and the grout overflows from the grouting hole and seeps into the rock and soil. At the same time, the grout that does not seep in in time flows to the grout stop brush (14). Under the action of the grout, the clamping plate (144) bends backward and its end is attached to the borehole wall. The grout overflowing from the end of the clamping plate (144) and the borehole wall is blocked by the multi-layer steel wire layer (143). At the same time, the protective plate (142) supports the multi-layer steel wire layer (143). The grout overflowing from the previous grout stop brush (14) is blocked by the adjacent grout stop brush (14) in turn. Step S2: Install steel arch frame and steel mesh close to the excavated tunnel wall, spray concrete after forming to form primary lining (2); the rear end of the anchor rod (13) is fixedly connected to the primary lining (2); Step S3: Install a waterproof and shock-absorbing layer (3) on the inner surface of the primary lining (2); Step S4: Install a ring of prefabricated secondary lining (42) in the fault fracture zone area. Install an inverted arch block (4216) at the bottom of the tunnel, with its left arm higher and its right arm lower. Based on the inverted arch block (4216), connect the side wall block B (4215) and the arch waist block B (4213) in sequence on its left side, and connect the side wall block A (4214) and the arch waist block A (4212) in sequence on its right side. The arch waist block B (4213) on the left side and the arch waist block A (4212) on the right side are connected by a capping block (4211). The capping block (4211) is located on the right side of the tunnel design centerline, completing the installation of the ring of prefabricated concrete section (421). Install the shear rubber section (422) on the prefabricated secondary lining (42). Install adjacent ring segmented prefabricated secondary linings (42) on the installed shear rubber segment (422). Install an inverted arch block (4216) at the bottom of the tunnel, with its left arm lower and its right arm higher. Based on the inverted arch block (4216), connect the side wall A block (4214) and the arch waist A block (4212) in sequence on its left side, and connect the side wall B block (4215) and the arch waist B block (4213) in sequence on its right side. The arch waist B block (4213) and the arch waist A block (4212) are connected by a capping block (4211). The capping block (4211) is located on the left side of the tunnel design centerline, completing the installation of one ring prefabricated concrete segment (421). Install the shear rubber segment (422) on the segmented prefabricated secondary lining (42). Repeat the above installation until the installation of the segmented prefabricated secondary lining (42) in the fault fracture zone area is completed; Step S5: In the tunnel, and in the area outside the fault fracture zone, an integral secondary lining (41) is constructed, one end of which is attached to the shear rubber segment (422) at the end of the fault fracture zone.

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