Support structure of tunnel crossing fault fracture zone and construction method thereof

Abstract

The application discloses a tunnel supporting structure crossing a fault fracture zone and a construction method, wherein the tunnel section is sequentially provided with a sweeping foam concrete layer, a first waterproof layer, a foam concrete outer layer, a second waterproof layer, an elastic shock-absorbing cushion layer and a foam concrete inner layer from outside to inside; the elastic shock-absorbing cushion layer is provided with an initial supporting steel arch; a radial prestressed anchor rod shock-absorbing device penetrating through the tunnel section is arranged on the tunnel peripheral surface at intervals; two adjacent initial supporting steel arches are connected through a plurality of supports; and the prestressed anchor rod shock-absorbing device is fixed on the initial supporting steel arch through the supports. The application can achieve the effects of anti-movement shock-absorbing buffering and the like through the design of the buffering shock-absorbing layer, improve the anti-seismic performance of the tunnel supporting structure crossing the fault fracture zone, effectively improve the anti-movement shock-absorbing effect, prevent the water in the surrounding rock from penetrating into the tunnel, prevent the metal structure from rusting, prevent the strength of the supporting structure from being reduced due to the rust and causing damage, facilitate installation and reduce the economic cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel support, and in particular relates to a tunnel support structure passing through a fault fracture zone and a construction method thereof. Background Art

[0002] my country has built numerous highway and railway tunnels in western China. The movement of Earth's plates has created numerous earthquake zones in this region, making it a prominent area of ​​compression and forming numerous fault fracture zones. Tunnel construction under these adverse geological conditions can lead to damage to underground structures due to seismic fault movement or long-term creep and slip of active faults, resulting in permanent deformation. This often causes tensile, torsional, shear, and flexural damage to tunnels passing through these zones, and in severe cases, can even lead to significant displacement or total collapse. Therefore, ensuring the safety of tunnel construction and underground projects within fault fracture zones is particularly important.

[0003] In order to solve the safety and stability issues of tunnels crossing fault fracture zones in western China, the key technical issues that need to be addressed mainly include: 1. Solving the problem of vibration damage to tunnels caused by earthquakes; 2. Overcoming the tension and shear damage caused by fault dislocation caused by earthquakes or the dislocation of the fault itself. At present, the main measures for shock absorption and dislocation resistance of underground and tunnel structures include shock absorption layer design, hinged design, and over-excavation design. Among them, the hinged design method requires the construction of a large-area annular dislocation platform, which has extremely high requirements for the construction cost and time cost of the tunnel, and this structure is mostly used in submarine tunnels; the shock absorption layer design method is mainly used in the initial support. By designing corresponding shock absorption and buffering structures outside the initial support, the buffering energy absorption capacity and anti-dislocation capacity of the tunnel are improved; the over-excavation design is generally based on the premise that the fault dislocation surface undergoes permanent deformation. According to the maximum possible dislocation of the fault, the tunnel section size is enlarged. In view of this, when a tunnel passes through a fault fracture zone, there is an urgent need for a tunnel support method that has anti-dislocation and shock absorption when passing through the fault fracture zone. This has important practical significance for increasing the stability and safety of the tunnel project and reducing the transportation safety risks after completion. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a tunnel support structure passing through a fault fracture zone and a construction method thereof to address the deficiencies in the prior art.

[0005] In order to achieve the above object, the purpose of the present invention is achieved through the following technical solutions:

[0006] On the one hand, a tunnel support structure passing through a fault fracture zone is provided, in which a sweeping foam concrete layer, a first waterproof layer, a foam concrete outer layer, a second waterproof layer, an elastic shock-absorbing pad layer and a foam concrete inner layer are sequentially arranged along the tunnel section from the outside to the inside, and a primary support steel arch frame is arranged in parallel within the elastic shock-absorbing pad layer. Prestressed anchor shock-absorbing devices radially penetrating the tunnel section are arranged at intervals along the circumference of the tunnel, and two adjacent primary support steel arch frames are connected by a plurality of brackets, and the prestressed anchor shock-absorbing devices are fixed to the primary support steel arch frames through the brackets, so that the prestressed anchor shock-absorbing devices can function and transmit force to the primary support steel arch frames through the brackets.

[0007] As described in the support structure for a tunnel crossing a fault fracture zone, the prestressed anchor rod shock-absorbing device includes an anchor rod and a tray, a spring and a sleeve sleeved on the anchor rod. One end of the anchor rod is fixed in a stable surrounding rock mass, and the other end passes through and is fixed on the bracket. The tray passes through the anchor rod and is tightly attached to the surrounding rock mass. The sleeve is arranged between the tray and the bracket and sleeved on the outside of the spring. The length of the spring in its natural state is greater than the thickness of the outer layer of the foam concrete, and the length of the sleeve is less than the thickness of the outer layer of the foam concrete.

[0008] As in the tunnel support structure crossing the fault fracture zone, the top surface of the bracket is located at the junction of the elastic shock-absorbing cushion layer and the second waterproof layer.

[0009] As in the support structure for a tunnel crossing a fault fracture zone, the bracket is a U-shaped steel bracket, and the two ends of the U-shaped steel bracket are respectively welded to the primary support steel arch frame.

[0010] As described in the tunnel support structure crossing the fault fracture zone, a channel steel arch frame is provided on the outer side between the two primary support steel arch frames to connect the adjacent U-shaped steel supports.

[0011] As described in the support structure for a tunnel crossing a fault fracture zone, the channel steel arch frame is formed by overlapping a large-sized first channel steel and a small-sized second channel steel, and both ends of the first channel steel and the second channel steel are provided with long holes.

[0012] As described in the tunnel support structure passing through the fault fracture zone, the elastic shock-absorbing cushion layer is made of flexible synthetic material or high-damping flexible material, the flexible synthetic material includes solid synthetic rubber, and the high-damping flexible material includes liquid asphalt system and liquid rubber system.

[0013] In another aspect, a method for constructing a tunnel support structure through a fault fracture zone is provided. The method comprises:

[0014] S1, install the primary steel arch, uniformly punch along the arch top of the surrounding rock to the arch foot of the side wall according to the designed depth, then install the prestressed anchor rod damping device, after fixing the position of the anchor rod, carry out the grouting process, when the grout reaches a certain design strength value, twist the tray into the anchor rod and tighten it, so that the tray is in close contact with the surrounding rock wall surface;

[0015] S2, use the foam concrete to scan the surrounding rock wall surface, so that the scanned foam concrete layer just covers the tray, install the first waterproof layer on the surface of the scanned foam concrete layer, so that the first waterproof layer is in close contact with the scanned foam concrete layer;

[0016] S3, the spring is sleeved on the exposed end of the anchor rod, one side of the spring is in close contact with the tray, then a sleeve pipe is sleeved outside the spring, finally a nut and a gasket are installed on the exposed end of the anchor rod, the nut is screwed until it is in contact with the spring;

[0017] S4, put the U-shaped steel support between the two primary steel arches, so that the exposed end of the anchor rod passes through the top opening of the U-shaped steel support, after fixing the position, weld the gasket at both feet of the U-shaped steel support to the outer side of the two primary steel arches, and then tighten the nut to contact the U-shaped steel support;

[0018] S5, according to the position and length of the channel steel design, use the channel steel arch to connect adjacent U-shaped steel supports;

[0019] S6, spray the outer layer of foam concrete within the length range outside the first waterproof layer and the U-shaped steel support, after the outer layer of foam concrete reaches the design strength, install the second waterproof layer outside the U-shaped steel support, and ensure that the second waterproof layer is in close contact with the surface of the outer layer of foam concrete; then, lay the elastic damping cushion layer within the length range of the U-shaped steel support; finally, spray the inner layer of foam concrete within the thickness range of the primary steel arch, which covers the primary steel arch completely.

[0020] According to the tunnel supporting structure construction method crossing the fault fracture zone, the length of the sleeve pipe is about 2cm less than the thickness of the outer layer of foam concrete.

[0021] As the tunnel supporting structure construction method crossing the fault fracture zone, the number of the U-shaped steel support installed in S4 is even; in S5, firstly, two adjacent U-shaped steel supports are divided into a group, a first channel steel is used to connect the two U-shaped steel supports in each group, the exposed ends of the two anchor rods passing through the U-shaped steel supports are respectively passed through the long holes at the two ends of the first channel steel, and then the nuts are tightened and fixed; secondly, the nuts at the connection positions of the two U-shaped steel supports adjacent to the two groups of U-shaped steel supports are unscrewed, then a second channel steel is installed, the exposed ends of the anchor rod bodies passing through the U-shaped steel supports are sequentially passed through the long holes of the first channel steel and the second channel steel, and then the unscrewed nuts are re-installed and fixed; finally, the installation of the annular channel steel arch is completed according to the above construction process, and after the completion, the nuts are tightened and checked, and the exposed ends of the anchor rods are passed through the middle positions of the long holes during the installation process.

[0022] The beneficial effects of the technical scheme of the present application are:

[0023] 1. The present application achieves the effects of anti-faulting, shock absorption and buffering by designing a buffering and shock absorption layer, and the corresponding construction method can guide the on-site construction of the present application, the simple shock absorption structure can be prefabricated outside the site, and the on-site construction is relatively convenient and fast, and the economic cost is relatively low compared with some existing complex technologies and related materials and equipment.

[0024] 2. The prestressed anchor rod shock absorption device provided by the present application can provide prestressed reinforcement to the anchoring force of the surrounding rock, and under the action of earthquake or faulting, the high-strength spring can deform to a certain extent to play a shock absorption role, further, the arc-shaped steel interlaced with each other at the clamping position of the U-shaped steel support can slide relatively to realize second-stage cooperative deformation, and the anti-seismic performance of the tunnel supporting structure in the fault fracture zone is improved.

[0025] 3. The two fulcrums of the U-shaped steel support are fixed on the two adjacent arches, the force on the prestressed supporting structure is dispersed to the two adjacent arches to improve the stress condition of the structure and the integrity of the whole structure; the first channel steel and the second channel steel are overlapped with each other to form a second layer of channel steel arches, and the supporting capacity of the supporting structure is improved; the long holes are designed at the overlapped positions of the channel steels, which not only facilitates the installation, but also can provide a small fault deformation and buffering and energy absorption effect under pressure.

[0026] 4. The design of the buffering layer can effectively improve the anti-faulting and shock absorption effect through the combination of the foam concrete and the elastic shock absorption pad, and the matching position relationship and the spraying thickness design between the shock absorption structure; the design of the first waterproof layer and the second waterproof layer can prevent the water in the surrounding rock from penetrating into the metal structure to prevent corrosion, thereby preventing the strength of the supporting structure from being reduced and damaged due to corrosion. BRIEF DESCRIPTION OF DRAWINGS

[0027] To further illustrate the above-mentioned objectives, structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings.

[0028] Figure 1 This is a cross-sectional view of a tunnel according to a preferred embodiment of the present invention;

[0029] Figure 2 A partial three-dimensional diagram of a preferred embodiment of the present invention;

[0030] Figure 3 This is a cross-sectional view of a prestressed anchor rod shock absorbing device according to a preferred embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the connection between the prestressed anchor rod shock-absorbing device and the U-shaped steel bracket in a preferred embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the overlap of the channel steel arch frame in a preferred embodiment of the present invention;

[0033] In the figure: 1. Sweeping foam concrete layer; 2. First waterproof layer; 3. Outer foam concrete layer; 4. Second waterproof layer; 5. Elastic shock-absorbing pad layer; 6. Inner foam concrete layer; 7. Primary support steel arch frame; 8. Prestressed anchor rod shock-absorbing device; 8-1. Anchor rod; 8-2. Tray; 8-3. Spring; 8-4. Casing; 8-5. First nut; 8-6. Washer; 8-7. Second nut; 9. Bracket; 10. Clamp; 11. Channel steel arch frame; 11-1. First channel steel; 11-2. Second channel steel; 11-3. Long hole. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0035] See Figure 1 、 Figure 2 As shown, the support structure for a tunnel crossing a fault fracture zone of the present invention is provided with a sweeping foam concrete layer 1, a first waterproof layer 2, a foam concrete outer layer 3, a second waterproof layer 4, an elastic shock-absorbing pad layer 5 and a foam concrete inner layer 6 in sequence along the tunnel section from the outside to the inside, a primary support steel arch frame 7 is arranged in parallel in the elastic shock-absorbing pad layer 5, and prestressed anchor shock-absorbing devices 8 radially penetrating the tunnel section are arranged at intervals along the circumference of the tunnel, two adjacent primary support steel arch frames 7 are connected by a plurality of brackets 9, and the prestressed anchor shock-absorbing devices 8 are fixed to the primary support steel arch frames 7 through the brackets 9, so that the prestressed anchor shock-absorbing devices 8 can function and transmit force to the primary support steel arch frames 7 through the brackets 9.

[0036] See Figure 3 、 Figure 4As shown, in the preferred embodiment, the prestressed anchor rod damping device 8 comprises an anchor rod 8-1 and a tray 8-2, a spring 8-3 (high-strength material) and a sleeve 8-4 sleeved on the anchor rod 8-1, one end of the anchor rod 8-1 is fixed in the stable surrounding rock mass, the other end passes through and is fixed on the support 9, the tray 8-2 with a central hole passes through the anchor rod 8-1 and abuts against the surrounding rock mass, the spring 8-3, the sleeve 8-4, the first nut 8-5 (high-strength material) and the gasket 8-6 are sequentially installed, the sleeve 8-4 is arranged between the tray 8-2 and the support 9 and is sleeved outside the spring 8-3, the length of the spring 8-3 in the natural state is greater than the thickness of the foam concrete outer layer 3, and the length of the sleeve 8-4 is less than the thickness of the foam concrete outer layer 3 (preferably about 2 cm). The sleeve 8-4 in the case preferably adopts a PVC pipe.

[0037] The support 9 has the functions of buffering, absorbing energy and transmitting force through its own structure, and is slightly smaller than the supporting effect of the primary support steel arch 7 and the anchor rod 8-1, but plays the functions of connection, force transmission and buffering.

[0038] The top surface of the support 9 is located at the junction of the elastic damping cushion layer 5 and the second waterproof layer 4.

[0039] Continuing to refer to Figure 4 As shown, in the preferred embodiment, the support 9 is a U-shaped steel support, and the two ends of the U-shaped steel support are respectively welded on the primary support steel arch 7, and the U-shaped steel support connects the two adjacent steel arches to improve the overall connection effect. Further, the U-shaped steel support is fixedly connected by three arc-shaped steels in sequence through the clamps 10, and further, the arc-shaped steels at the clamps 10 of the U-shaped steel support are relatively slid to realize the second-stage cooperative deformation and improve the anti-seismic performance of the fault fracture zone tunnel supporting structure. The U-shaped steel support is pre-holed at the top end, and the hole diameter is greater than the diameter of the anchor rod 8-1, the exposed end of the anchor rod 8-1 passes through the hole of the U-shaped steel support, and the two sides are fixedly connected by the first nut 8-5 and the second nut 8-7 (high-strength material).

[0040] The outer side between the two primary support steel arches 7 is provided with a channel steel arch 11 for connecting the adjacent U-shaped steel supports. Specifically, referring to Figure 5As shown, the channel steel arch 11 is formed by mutually lapping a large first channel steel 11-1 and a small second channel steel 11-2, and both ends of the first channel steel 11-1 and the second channel steel 11-2 are provided with long holes 11-3. Specifically, the channel steel is designed to adopt two different types of channel steels, so that the small second channel steel 11-2 can be lapped in the inner diameter of the large first channel steel 11-1 and be fixedly connected by using the second nut 8-7. According to the design, the channel steel is bent to a certain extent, and the bending radius is consistent with the outer ring connection of the adjacent U-shaped steel support. The hole position is determined according to the spacing of the adjacent U-shaped steel support at both ends of the channel steel, and a long hole is opened according to the diameter of the anchor rod 8-1. The shape of the hole is preferably a waist-shaped hole, the width of the waist-shaped hole is greater than the diameter of the anchor rod 8-1, and the length of the rectangular middle part of the waist-shaped hole is a reserved displacement length, which can be 100 mm.

[0041] The elastic shock-absorbing cushion layer 5 is made of flexible synthetic material or large-damping flexible material. The flexible synthetic material includes solid synthetic rubber, etc., and the large-damping flexible material includes liquid asphalt, liquid rubber, etc.

[0042] During construction, the following steps are specifically included:

[0043] S1. According to the construction design, after the initial support steel arch 7 of the tunnel is installed, holes are punched at a uniform position along the surrounding rock arch top to the surrounding rock arch foot according to the designed depth, and then the pre-stressed anchor rod shock-absorbing device is installed. After the position of the anchor rod 8-1 is fixed, the grouting process is performed. After the grouting is completed, when the grout reaches a certain design strength value, the tray 8-2 is screwed into the anchor rod 8-1 and tightened, so that the tray 8-2 is in close contact with the surrounding rock wall surface.

[0044] S2. The surrounding rock wall surface is scanned by using the foam concrete, and the scanned foam concrete layer 1 is just covered on the tray 8-2. The first waterproof layer 2 is further installed on the surface of the scanned foam concrete layer 1, so that the first waterproof layer 2 is in close contact with the scanned foam concrete layer 1.

[0045] S3. The high-strength spring 8-3 is sleeved on the exposed end of the anchor rod 8-1, one side of the high-strength spring 8-3 is in close contact with the tray 8-2, and the natural state length of the high-strength spring 8-3 should be greater than the thickness of the foam concrete outer layer 3. Then, the sleeve pipe 8-4 (PVC pipe) is sleeved outside the high-strength spring 8-3, and the length of the sleeve pipe 8-4 should be less than the thickness of the foam concrete outer layer 3 by about 2 cm. Finally, the first nut 8-5 and the gasket 8-6 are installed on the exposed end of the anchor rod 8-1, and the first nut 8-5 is screwed until it comes into contact with the high-strength spring 8-3.

[0046] S4, the exposed anchor rod 8-1 is passed through the top opening of the U-shaped steel support from the two sets of initial support steel arches 7, after the position is fixed, the base plate at the two feet of the U-shaped steel support is welded and fixed with the outer side of the two sets of initial support steel arches 7, and the design installation quantity of the U-shaped steel support is ensured to be even, and then the first nut 8-5 is tightened to contact and fix the U-shaped steel support.

[0047] S5, according to the position and length of the channel steel, different models and different lengths of channel steel are prefabricated in advance, and the adjacent U-shaped steel supports are connected by using the channel steel: first, two adjacent U-shaped steel supports are connected by using the first channel steel 11-1, the exposed ends of the anchor rods 8-1 passing through the holes of the two U-shaped steel supports are respectively passed through the long holes 11-3 on both sides of the first channel steel 11-1, and then the second nut 8-7 is tightened and fixed; secondly, the second nut 8-7 at the connection between the two adjacent U-shaped steel supports is unscrewed, and then the second channel steel 11-2 is installed, the exposed ends of the anchor rods 8-1 passing through the U-shaped steel supports are sequentially passed through the long holes 11-3 of the first channel steel 11-1 and the second channel steel 11-2, and then the unscrewed second nut 8-7 is reinstalled and fixed; finally, the installation of the ring-shaped channel steel arch 11 is completed according to the construction process, and the second nut 8-7 needs to be tightened and checked after the installation, and the exposed ends of the anchor rods 8-1 need to be passed through the middle position of the long hole 11-3 as much as possible during the installation.

[0048] S6, the foam concrete outer layer 3 is sprayed in the length range outside the first waterproof layer 2 and the U-shaped steel support, after the outer foam concrete outer layer 3 reaches the design strength, the second waterproof layer 4 is installed outside the U-shaped steel support, and the second waterproof layer 4 is tightly attached to the surface of the foam concrete outer layer 3; then, the elastic shock-absorbing cushion layer 5 is laid in the length range of the U-shaped steel support; finally, the foam concrete inner layer 6 is sprayed in the thickness range of the initial support steel arch 7 to cover the initial support steel arch 7.

[0049] The above is only the preferred embodiment of the present application, and does not limit the implementation and protection scope of the present application. For those skilled in the art, it should be realized that any equivalent replacement and obvious change made by referring to the content of the present application should be included in the protection scope of the present application.

Claims

1. A tunnel support structure passing through a fault fracture zone, characterized in that: A sweeping foam concrete layer, a first waterproof layer, a foam concrete outer layer, a second waterproof layer, an elastic shock-absorbing pad layer and a foam concrete inner layer are sequentially arranged along the tunnel section from the outside to the inside, and a primary support steel arch frame is arranged in parallel in the elastic shock-absorbing pad layer. Prestressed anchor shock-absorbing devices that radially penetrate the tunnel section are arranged at intervals along the circumference of the tunnel, and two adjacent primary support steel arch frames are connected by a plurality of brackets. The prestressed anchor shock-absorbing devices are fixed to the primary support steel arch frames through the brackets, so that the prestressed anchor shock-absorbing devices play a role and transmit force to the primary support steel arch frames through the brackets; the prestressed anchor shock-absorbing devices include anchor rods and sleeves on The tray, spring and sleeve on the anchor rod, one end of the anchor rod is fixed in the stable surrounding rock mass, and the other end passes through and is fixed on the bracket, the tray passes through the anchor rod and is close to the surrounding rock mass, the bracket is a U-shaped steel bracket, the two ends of the U-shaped steel bracket are respectively welded to the primary support steel arch frame, the U-shaped steel bracket is composed of three sections of arc steel fixedly connected in sequence by clamps and can slide relative to each other when subjected to force, the sleeve is arranged between the tray and the bracket and is sleeved on the outside of the spring, the length of the spring in the natural state is greater than the thickness of the outer layer of the foam concrete, and the length of the sleeve is less than the thickness of the outer layer of the foam concrete.

2. The support structure for a tunnel crossing a fault fracture zone according to claim 1, characterized in that: The top surface of the bracket is located at the junction of the elastic shock-absorbing pad layer and the second waterproof layer.

3. The support structure for a tunnel crossing a fault fracture zone according to claim 1, characterized in that: A channel steel arch frame is provided on the outer side between the two primary supporting steel arch frames for connecting adjacent U-shaped steel supports.

4. The support structure for a tunnel crossing a fault fracture zone according to claim 3, characterized in that: The channel steel arch frame is formed by overlapping a large-sized first channel steel and a small-sized second channel steel, and both ends of the first channel steel and the second channel steel are provided with long holes.

5. The support structure for a tunnel crossing a fault fracture zone according to claim 4, characterized in that: The elastic shock-absorbing cushion layer is made of flexible synthetic material, and the flexible synthetic material includes solid synthetic rubber.

6. A method for constructing a tunnel support structure through a fault fracture zone, characterized in that: The support structure for a tunnel crossing a fault fracture zone according to claim 5 is implemented, comprising: S1. Install the primary steel arch frame, drill holes at even locations along the surrounding rock arch top to the side wall arch foot according to the designed depth, then install the prestressed anchor rod shock-absorbing device. After the anchor rod position is fixed, carry out the grouting process. When the grout reaches a certain designed strength value, screw the tray into the anchor rod and tighten it to ensure close contact between the tray and the surrounding rock wall; S2. Sweeping the surrounding rock wall with foam concrete until the swept foam concrete layer just covers the pallet, and installing a first waterproof layer on the surface of the swept foam concrete layer so that the first waterproof layer is in close contact with the swept foam concrete layer; S3. Put the spring on the exposed end of the anchor rod, with one side of the spring close to the tray. Then put the sleeve on the spring. Finally, install the nut and gasket on the exposed end of the anchor rod. Tighten the nut until it contacts the spring. S4. Place the U-shaped steel bracket between the two primary steel arches, passing the exposed end of the anchor rod through the top opening of the U-shaped steel bracket. After fixing the position, weld the pads at the two feet of the U-shaped steel bracket to the outer sides of the two primary steel arches respectively, and then tighten the nuts to contact and fix them with the U-shaped steel bracket; S5. Use channel steel arches to connect adjacent U-shaped steel supports according to the designed position and length of the channel steel. S6. Spray the outer layer of foam concrete within the length range of the first waterproof layer and the outer side of the U-shaped steel support. After the outer layer of foam concrete reaches the design strength, install the second waterproof layer on the outer side of the U-shaped steel support, and ensure that the second waterproof layer is in close contact with the surface of the outer layer of foam concrete; then, lay the elastic shock-absorbing pad within the length range of the U-shaped steel support; finally, spray the inner layer of foam concrete within the thickness range of the primary supporting steel arch frame to completely cover the primary supporting steel arch frame.

7. The method for constructing a tunnel support structure through a fault fracture zone according to claim 6, characterized in that: The length of the sleeve is less than 2 cm of the thickness of the outer layer of the foam concrete.

8. The method for constructing a tunnel support structure through a fault fracture zone according to claim 6, characterized in that: In S4, the number of U-shaped steel brackets installed is an even number; in S5, first, the two adjacent U-shaped steel brackets are divided into a group, and the two U-shaped steel brackets in each group are connected with the first channel steel, so that the exposed ends of the two anchor rods passing through the U-shaped steel brackets pass through the long holes at both ends of the first channel steel respectively, and then tighten and fix them with nuts; secondly, the nuts at the connection of the two U-shaped steel brackets on the adjacent sides of the two adjacent groups of U-shaped steel brackets are unscrewed, and then the second channel steel is installed, and the exposed ends of the anchor rod bodies passing through the adjacent side U-shaped steel brackets are passed through the long holes of the first channel steel and the second channel steel in turn, and then the unscrewed nuts are reinstalled and fixed; finally, the installation of the circumferential channel steel arch frame is completed according to the above construction process, and the nuts are tightened and checked after completion. During the installation process, the exposed ends of the anchor rods are passed through the middle position of the long holes.

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