Composite supporting structure for crossing strike-slip fault tunnel and construction method of composite supporting structure

Abstract

The invention discloses a composite supporting structure for a strike-slip fault crossing tunnel and a construction method of the composite supporting structure. The composite supporting structure comprises a tunnel expanding excavation area arranged around a fault. A first concrete layer, a yielding profile steel arch frame assembly, a second concrete layer, a yielding concrete layer and a secondary lining are sequentially arranged in the tunnel expanding excavation area from outside to inside in the radial direction. The yielding type steel arch frame assembly comprises a plurality of steel arch frames, a plurality of first yielding devices are arranged between the steel arch frames and the first concrete layer, and a plurality of second yielding devices are arranged between any two adjacent steel arch frames. The supporting structure is used for solving the problems of surrounding rock deformation and support damage caused by fault slippage in the tunnel operation period in the prior art, and the purposes of improving the resistance of the supporting structure to fault strike-slip in the tunnel operation period and improving the tunnel operation safety are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of tunnel construction, in particular to a composite support structure for a tunnel crossing strike-slip fault and a construction method thereof. BACKGROUND

[0002] With the steady advancement of infrastructure construction, complex geological structures such as strike-slip fault with fracture zone will inevitably be encountered during tunnel construction. During tunnel operation, if fault slip occurs, it is easy to cause the tunnel support structure to be damaged, which may lead to cracking of the support, or even loss of bearing capacity and affect traffic.

[0003] In the prior art, the new Austrian tunneling method (NATM) is commonly used for support structure design and construction organization planning in tunnel engineering. The conventional tunnel support structure includes system anchor, steel arch initial support, secondary lining, etc. The existing NATM tunnel support structure is difficult to resist the deformation of surrounding rock caused by fault slip during tunnel operation period, although it can effectively control the deformation of surrounding rock during construction period. SUMMARY

[0004] The present application provides a composite support structure for a tunnel crossing strike-slip fault and a construction method thereof, to solve the problem of deformation of surrounding rock and damage of support caused by fault slip during tunnel operation period in the prior art, and to achieve the purpose of improving the resistance of support structure to strike-slip fault during tunnel operation period and improving the safety of tunnel operation.

[0005] The present application is achieved by the following technical solutions:

[0006] A composite support structure for a tunnel crossing strike-slip fault, comprising a tunnel expansion area arranged around the fault; at the tunnel expansion area, a first concrete layer, a pressure-relief type steel arch assembly, a second concrete layer, a pressure-relief concrete layer and a secondary lining are arranged in the radial direction from outside to inside in sequence.

[0007] The pressure-relief type steel arch assembly comprises a plurality of steel arches, a plurality of first pressure-relief devices are arranged between the steel arches and the first concrete layer, and a plurality of second pressure-relief devices are arranged between any two adjacent steel arches.

[0008] In view of the problem that the tunnel crossing strike-slip fault is prone to lead to deformation of surrounding rock and damage of support due to fault slip in the prior art, the application first proposes a composite support structure for the tunnel crossing strike-slip fault. The structure is first excavated according to the original design contour line, and the tunnel is expanded in the area crossing the fracture zone of the strike-slip fault to obtain a tunnel expansion area. The specific expansion position and expansion amount can be determined according to the strike-slip direction and the estimated strike-slip amount, and are not specifically limited herein. The core principle is to make the tunnel expansion area located in the area where the support structure is subjected to the force due to fault slip. A first concrete layer is arranged on the inner wall of the tunnel expansion area, and a yield steel arch assembly, a second concrete layer, a yield concrete layer and a secondary lining are sequentially arranged in the first concrete layer. The first concrete layer is directly sprayed on the tunnel rock wall as a facing to improve the flatness of the tunnel rock wall and facilitate the installation of the yield steel arch assembly. The yield steel arch assembly, the second concrete layer and the yield concrete layer jointly constitute an initial support structure. The yield steel arch assembly is provided with a first yield device and a second yield device on the basis of the traditional steel arch, the second concrete layer is used to cover and consolidate the yield steel arch assembly, and the yield concrete layer is further covered on the second concrete layer.

[0009] The first yield device and the second yield device in the application refer to devices capable of absorbing the extrusion force of fault slip on the support structure through their own deformation. The yield concrete layer in the application refers to a concrete material capable of absorbing external extrusion stress through its own compression deformation.

[0010] The specific working principle of the application is as follows: if the tunnel encounters strike-slip during operation, the surrounding rock corresponding to the tunnel expansion area will obviously slip, generating strong extrusion and shear on the support structure. In this process, the yield steel arch assembly absorbs the energy of fault slip through the extrusion and torsion deformation of the first yield device and the second yield device in the yield steel arch assembly, so that the steel arch structure of the initial support is not subjected to destructive shear. In addition, the yield concrete layer can absorb the radial inward extrusion stress generated by fault slip, and the energy is dissipated through the compression deformation of the yield concrete layer.

[0011] It can be seen that the application can significantly enhance the resistance to tunnel surrounding rock deformation caused by fault slip during tunnel operation, thereby ensuring the stability and safety of the support structure of the tunnel crossing strike-slip fault in the long-term operation process, and reducing the risk of damage to the support structure.

[0012] Further, the yield concrete layer is EPS concrete.

[0013] The EPS concrete used in this scheme is lightweight concrete that uses polystyrene particles to replace some or all of the coarse aggregate in traditional concrete. It has the characteristics of low density and lightweight filling, and has good compressibility. Therefore, it can generate a relatively large amount of compressive deformation when it encounters fault slip compression, thereby consuming and releasing the surrounding rock load, further reducing the risk of torsion, fracture and other damage to the support structure caused by fault slip shear, and thus significantly improving the overall stability and reliability of the support structure.

[0014] Furthermore, the tunnel widening zone is located on the slide plate of the fault; and along the tunnel direction:

[0015] The tunnel widening zone gradually decreases in depth from the end closest to the fault to the end furthest from the fault.

[0016] The thickness of the pressure-reducing concrete layer gradually decreases from the end closest to the fault to the end furthest from the fault.

[0017] The thicknesses of the first concrete layer, the profiled steel arch frame assembly, and the second concrete layer remain unchanged.

[0018] This solution involves widening the tunnel along the fault's slipway and installing the composite support structure described in this application, which effectively resists fault slippage with lower construction costs. Furthermore, both the widened tunnel zone and the relief concrete layer gradually thin from the end closest to the fault to the end furthest from it, further reducing construction costs.

[0019] Meanwhile, when the fault slips, the thickness of the relief concrete layer is thicker at the end near the fault fracture zone. Therefore, in the area near the fault fracture zone, the compression and shear forces exerted by the fault slip on the support structure are mainly absorbed by the compression deformation of the relief concrete layer. At the end away from the fault fracture zone, the relief concrete layer gradually thins, and the secondary lining inside gradually begins to be subjected to greater forces, causing the secondary lining to deflect slightly and overcome the adverse effects of the fault slip. It can be seen that by limiting the thickness of the relief concrete layer, this scheme, while avoiding the secondary lining from being sheared by the fault, endows the reinforced concrete secondary lining with a certain deflection deformation capacity under fault slip, significantly improving the safety and stability of the composite support structure of this application under fault slip conditions.

[0020] Those skilled in the art should understand that the two sides of a fault are the hanging wall and the footwall, respectively. In this application, the sloping side of a fault refers to the side that slides downwards. For a normal fault, the sloping side is the hanging wall; for a reverse fault, the sloping side is the footwall.

[0021] Further, the first pressure relief device comprises a plurality of elliptical metal rings welded on the outer wall of the steel arch, the cross section of the elliptical metal ring is elliptical, and the short axis of the elliptical metal ring extends along the radial direction of the tunnel.

[0022] The present scheme uses an elliptical metal ring as the first pressure relief device, and the short axis thereof extends along the radial direction of the tunnel. When the fault slips and extrudes the supporting structure, better resistance can be provided to ensure good radial pressure relief capability in all directions of the tunnel cross section, which can not only resist fault slip, but also resist the extrusion of surrounding rock deformation on the supporting structure caused by stress release in all directions.

[0023] Further, the second pressure relief device comprises a plurality of connecting ribs connected between the adjacent two steel arches and pressure relief rings connected with the connecting ribs.

[0024] The present scheme connects the adjacent two steel arches through a plurality of connecting ribs, which can withstand the tension and pressure between the adjacent two steel arches, thereby significantly improving the stability and safety of the pressure relief type steel arch assembly. In addition, the present scheme further provides pressure relief rings on the connecting ribs. When the second concrete layer around the connecting ribs is deformed by being extruded or stretched, the connecting ribs are deformed to bear and consume the load, thereby reducing the risk of the connecting ribs being easily damaged by tension or pressure. At the same time, the relative extrusion between the pressure relief rings and the second concrete layer can also form a certain buffering effect, thereby further improving the resistance of the present scheme to fault slip.

[0025] Further, the cross section of the pressure relief ring is annular, and the axis of the pressure relief ring is perpendicular to the axis of the corresponding connecting rib.

[0026] Since the connecting rib is connected between the adjacent two steel arches, the axis of the connecting rib extends along the longitudinal direction (length direction) of the tunnel. The present scheme makes the axis of the pressure relief ring perpendicular to the axis of the connecting rib, which can more accurately extrude the pressure relief ring inward when the fault slips, thereby facilitating better consumption of the component force of the fault slip along the longitudinal direction of the tunnel, and further reducing the risk of misplacement or even breakage of the steel arch caused by fault slip.

[0027] Further, the pressure relief ring is made of steel or rubber material. Since one end of the pressure relief ring faces the inside of the tunnel, part of the concrete will enter the pressure relief ring and be solidified when the second concrete layer is sprayed in the later stage. Therefore, the pressure relief ring in the present scheme can be made of rubber material in addition to steel material, which can utilize the deformation ability of the rubber material to consume the energy of fault slip, thereby significantly reducing the production cost.

[0028] Furthermore, between two adjacent steel arch frames, two adjacent connecting bars are arranged in an alternating manner: one connecting bar is connected to the outer diameter end of the two adjacent steel arch frames, and the other connecting bar is connected to the inner diameter end of the two adjacent steel arch frames.

[0029] For the connecting bars that connect to the outer diameter ends of two adjacent steel arch frames, the pressure relief rings on them are located in the direction of the inner diameter side of the connecting bars;

[0030] For the connecting ribs that connect to the inner diameter ends of two adjacent steel arch frames, the pressure relief rings on them are located on the outer diameter side of the connecting ribs.

[0031] In this design, a ring of connecting bars along the tunnel circumference is staggered at the outer and inner diameter ends of the steel arch frame. This significantly increases the overall stability of the compression-type steel arch frame assembly and further enhances its resistance to fault slip. Furthermore, regardless of whether the connecting bars are located at the outer or inner diameter end of the steel arch frame, the pressure-relief ring is positioned directly opposite the steel arch frame, ensuring that the pressure-relief ring fully utilizes its pressure-relief energy dissipation function against fault slip.

[0032] Furthermore, foam board is filled between the outer diameter ends of two adjacent steel arch frames, and the second pressure relief device is located on the inner side of the foam board.

[0033] This design uses foam boards to fill the space between the outer diameter ends of two adjacent steel arch frames, ensuring that the connecting ribs and pressure relief rings are located inside the foam boards. The function of the foam boards is to shield the outside of the steel arch frames, preventing concrete from entering the area where the first pressure relief device is located during the subsequent spraying of the second concrete layer. This avoids completely fixing the first pressure relief device within the second concrete layer, which would prevent it from effectively dissipating pressure and energy. Sufficient deformation space is reserved for the first pressure relief device between the steel arch frame and the first concrete layer, significantly ensuring the application's resistance to fault slip.

[0034] A construction method for a composite support structure used in tunnels traversing strike-slip faults includes the following steps:

[0035] S1. Excavate the tunnel, and when the tunnel passes through the fractured zone of the strike-slip fault, expand the excavation to obtain the tunnel expansion zone;

[0036] S2. Spray the first layer of concrete onto the rock surface in the tunnel widening area;

[0037] S3. Erect the profiled steel arch frame assembly;

[0038] S4. Shotcrete second layer;

[0039] S5. Construct a pressure-relief concrete layer;

[0040] S6. Cast the secondary lining.

[0041] Compared with the prior art, the present application has at least the following advantages and beneficial effects:

[0042] 1、The composite support structure for crossing strike-slip fault tunnel and the construction method thereof can significantly enhance the resistance to the deformation of the tunnel surrounding rock caused by fault slip during the tunnel operation period, thereby ensuring the stability and safety of the tunnel support structure crossing the strike-slip fault during the long-term operation process and reducing the risk of damage to the support structure.

[0043] 2、The composite support structure for crossing strike-slip fault tunnel and the construction method thereof can achieve effective resistance to fault slip with smaller construction cost by expanding the tunnel in the direction of the lower slip disc of the fault and setting the composite support structure of the present application. In addition, the tunnel expansion area and the yielding concrete layer gradually thin from one end close to the fault to one end away from the fault, which can further reduce the construction cost.

[0044] 3、The composite support structure for crossing strike-slip fault tunnel and the construction method thereof can provide better resistance when the strike-slip fault extrudes the support structure, ensuring good radial yielding capacity in all directions of the tunnel cross section, which can not only resist the strike-slip fault, but also resist the extrusion of the surrounding rock deformation caused by the release of ground stress in all directions on the support structure.

[0045] 4、The composite support structure for crossing strike-slip fault tunnel and the construction method thereof can withstand the tension and pressure between the two adjacent steel arches through the connecting rib, significantly improving the stability and safety of the yielding steel arch assembly. When the second concrete layer around the connecting rib is deformed by extrusion or stretching, the load is consumed by the deformation of the several yielding rings, which can reduce the risk of the connecting rib being easily damaged by tension or compression. At the same time, the relative extrusion of each yielding ring and the second concrete layer can also form a certain buffering effect, further improving the resistance of the present application to fault slip.

[0046] 5、The composite support structure for crossing strike-slip fault tunnel and the construction method thereof, with the connecting rib staggered and distributed in the outer diameter end and the inner diameter end of the steel arch, can significantly increase the overall stability of the yielding steel arch assembly and further improve the ability of the present application to resist fault slip.

[0047] 6、The composite support structure for crossing strike-slip fault tunnel and the construction method thereof can avoid the second concrete entering the area outside the steel arch where the first yielding device is provided by using the foam board, avoid completely fixing the first yielding device in the second concrete layer, which can cause the first yielding device to fail to play a good yielding and energy dissipation function, and reserve sufficient deformation space for the first yielding device between the steel arch and the first concrete layer, which can significantly ensure the resistance of the present application to fault slip. BRIEF DESCRIPTION OF DRAWINGS

[0048] The accompanying drawings, which are included to provide a further understanding of the embodiments of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

[0049] Figure 1 A schematic view of a tunnel cross section of an embodiment of the application;

[0050] Figure 2 A schematic view of the thickness of a tunnel excavation area along the tunnel direction in an embodiment of the application;

[0051] Figure 3 A schematic view of a first pressure relief device in an embodiment of the application;

[0052] Figure 4 A schematic view of a second pressure relief device when the connecting rib is located at the outer diameter end in an embodiment of the application;

[0053] Figure 5 A schematic view of a second pressure relief device when the connecting rib is located at the inner diameter end in an embodiment of the application;

[0054] Figure 6 A schematic view of the structure of the pressure relief ring and the connecting rib in an embodiment of the application;

[0055] Figure 7 A sectional view of the pressure relief ring and the connecting rib in an embodiment of the application;

[0056] Figure 8 A Figure 7 A local enlarged view of A in FIG. 5;

[0057] Figure 9 A schematic view of a tunnel excavation area in an embodiment of the application;

[0058] Figure 10 A schematic view of the construction process in an embodiment of the application;

[0059] Markings in the drawings and corresponding names of parts:

[0060] 1 - first concrete layer, 2 - pressure relief type steel arch assembly, 201 - steel arch, 202 - elliptical metal ring, 203 - connecting rib, 204 - pressure relief ring, 205 - foam board, 206 - sleeve, 207 - T-shaped hole, 208 - small diameter end, 209 - large diameter end, 210 - second positioning groove, 211 - positioning elastic sheet, 212 - welding point, 3 - second concrete layer, 4 - pressure relief concrete layer, 5 - secondary lining, 6 - original design excavation contour line, 7 - excavation contour line, 8 - anchor rod. DETAILED DESCRIPTION

[0061] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are for explaining the invention only and are not intended to limit the invention. In the description of this application, it should be understood that terms such as "front," "rear," "left," "right," "upper," "lower," "vertical," "horizontal," "high," "low," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application.

[0062] Example 1:

[0063] like Figure 1 The composite support structure shown includes a tunnel widening zone set around the fault; in the tunnel widening zone, a first concrete layer 1, a pressure-relief steel arch assembly 2, a second concrete layer 3, a pressure-relief concrete layer 4 and a secondary lining 5 are arranged in the radial direction from the outside to the inside.

[0064] The pressure-relief steel arch frame assembly 2 includes several steel arch frames 201. Several first pressure-relief devices are provided between the steel arch frames 201 and the first concrete layer 1, and several second pressure-relief devices are provided between any two adjacent steel arch frames 201.

[0065] In this embodiment, the pressure-relief concrete layer 4 is EPS concrete.

[0066] In this embodiment, as Figure 2 As shown, the tunnel widening zone is located on the slide plate of the fault; and along the tunnel direction:

[0067] The tunnel widening zone gradually decreases in depth from the end closest to the fault to the end furthest from the fault.

[0068] The thickness of the pressure-relief concrete layer 4 gradually decreases from the end closest to the fault to the end furthest from the fault.

[0069] The thicknesses of the first concrete layer 1, the profiled steel arch frame assembly 2, and the second concrete layer 3 remain unchanged.

[0070] In a more preferred embodiment, the length of the pressure-relief concrete layer 4 along the tunnel direction is 20 to 30 times the tunnel diameter. If the length is less than 20 times the tunnel diameter, the deflection deformation capacity given to the secondary lining is weak, making it difficult to cope with faults with large slip distances. If the length is greater than 30 times the tunnel diameter, it will lead to excessively high construction costs. Therefore, a length of 20 to 30 times the tunnel diameter is a range that achieves a good balance between economy and safety.

[0071] Embodiment 2:

[0072] A composite support structure for crossing a strike-slip fault tunnel, based on the structure of Embodiment 1:

[0073] The first pressure-relief device, as shown in Figure 3 , comprises a plurality of elliptical metal rings 202 welded to the outer wall of the steel arch 201. The cross section of the elliptical metal ring 202 is elliptical, and the short axis of the elliptical metal ring 202 extends in the radial direction of the tunnel, and the long axis of the elliptical metal ring 202 extends in the tangential direction of the tunnel contour line.

[0074] As shown in Figure 4 and Figure 5 , the second pressure-relief device comprises a plurality of connecting ribs 203 connected between adjacent two sets of steel arches 201, and a pressure-relief ring 204 connected to the connecting rib 203. The cross section of the pressure-relief ring 204 is annular, and the axis of the pressure-relief ring 204 is perpendicular to the axis of the corresponding connecting rib 203.

[0075] In this embodiment, the pressure-relief ring 204 is made of steel or rubber material. When the pressure-relief ring is made of rubber material, its wall thickness is greater than that of the steel pressure-relief ring.

[0076] In this embodiment, between adjacent two sets of steel arches 201, the adjacent two connecting ribs 203 are arranged alternately: one connecting rib 203, as shown in Figure 4 , is connected to the outer diameter end of the adjacent two sets of steel arches 201; the other connecting rib 203, as shown in Figure 5 , is connected to the inner diameter end of the adjacent two sets of steel arches 201. It should be noted that in Figure 4 and Figure 5 , the upper side direction in the figure is the direction close to the excavation contour line.

[0077] For the connecting rib 203 connected to the outer diameter end of the adjacent two sets of steel arches 201, the pressure-relief ring 204 thereon is located in the inner diameter side direction of the connecting rib 203; for the connecting rib 203 connected to the inner diameter end of the adjacent two sets of steel arches 201, the pressure-relief ring 204 thereon is located in the outer diameter side direction of the connecting rib 203.

[0078] As shown in Figure 4 and Figure 5 , a foam board 205 is also filled between the outer diameter ends of the adjacent two sets of steel arches 201, and the second pressure-relief device is located in the inner side direction of the foam board 205. Preferably, the foam board 205 can be connected to the side wall of the steel arch 201 by bonding or clamping.

[0079] The elliptical metal ring 202 and the yielding ring 204 in the embodiment are in tubular structure; and the elliptical metal ring 202 is preferably made of an elliptical steel pipe.

[0080] In a more preferable embodiment, the axis of each yielding ring 204 extends towards the radial direction of the tunnel.

[0081] Embodiment 3:

[0082] A composite support structure for a tunnel crossing a strike-slip fault, based on embodiment 2, as shown in Figure 6 and Figure 7 The outer wall of the yielding ring 204 is fixedly connected with a sleeve 206, and the sleeve 206 is in clearance fit with the connecting rib 203, so as to facilitate flexible adjustment of the specific position of the yielding ring 204 on the connecting rib 203.

[0083] In addition, after the yielding ring 204 is installed on the connecting rib 203, although the orientation and position of the yielding ring 204 can be manually positioned, during the process of later spraying of the second concrete layer, due to the pushing force of the sprayed concrete, the yielding ring 204 may be moved and / or rotated on the connecting rib 203, resulting in misalignment of each yielding ring 204, so that each yielding ring 204 is not arranged in a standard manner, which is not conducive to fully playing the function of the second yielding device during the tunnel operation. In order to overcome this problem, as shown in Figure 6 to Figure 8 a T-shaped hole 207 is further provided on the surface of the sleeve 206, one end of the T-shaped hole 207 with a smaller diameter faces outward, and the other end with a larger diameter faces inward; a T-shaped buckle is assembled in the T-shaped hole 207, the T-shaped buckle includes a small-diameter end 208 and a large-diameter end 209; a first positioning groove group and a second positioning groove group are provided on the sidewall of the one end of the T-shaped hole 207, which are distributed radially from outside to inside, the first positioning groove group includes a plurality of annularly distributed first positioning grooves, and the second positioning groove group includes a plurality of annularly distributed second positioning grooves 210, and the first positioning grooves and the second positioning grooves 210 are in one-to-one correspondence; a plurality of annularly distributed positioning elastic sheets 211 are provided on the outer wall of the small-diameter end 208, and the positioning elastic sheets 211 are matched with the first positioning grooves and the second positioning grooves 210; on the end face of the large-diameter end 209 radially inward, a meshing tooth for increasing friction is provided.

[0084] In the initial state, each positioning elastic sheet 211 is located in the corresponding first positioning groove, at this time, the meshing tooth and the connecting rib 203 have a gap and do not contact each other;

[0085] When the pressure relief ring 204 is installed in place, the worker presses the small-diameter end 208 inward, the T-shaped buckle moves inward as a whole, the positioning elastic sheets 211 are deformed to disengage from the first positioning grooves and enter the corresponding second positioning grooves 210; at this time, the engagement teeth are in close contact with the surface of the connecting rib 203, thereby achieving temporary positioning and installation of the pressure relief ring 204 and reducing the risk of interference of the pressure relief ring 204 by later sprayed concrete.

[0086] Embodiment 4:

[0087] A construction method of a composite support structure for crossing a strike-slip fault tunnel, for constructing the composite support structure described in any of the above embodiments, the construction method comprising the following steps:

[0088] Step S1, excavate the tunnel according to the original design contour line, and expand the excavation when crossing the fracture zone of the strike-slip fault to obtain a tunnel expansion area; as shown in Figure 9 The area between the original design excavation contour line 6 and the expansion contour line 7 is the tunnel expansion area;

[0089] Step S2, set the anchor rod 8, and spray the first concrete layer 1 on the surface of the rock stratum in the tunnel expansion area;

[0090] Step S3, erect the pressure-relief steel arch assembly 2 to obtain the structure as shown in Figure 10 ;

[0091] Step S4, spray the second concrete layer 3, which needs to completely cover the pressure-relief steel arch assembly 2;

[0092] Step S5, apply the pressure-relief concrete layer 4;

[0093] Step S6, pour the secondary lining 5.

[0094] Preferably, the thickness of the first concrete layer 1, the second concrete layer 3, the secondary lining 5, and the pressure-relief concrete layer 4 gradually increases along the radial direction of the tunnel.

[0095] In a more preferred embodiment, the specific process of erecting the pressure-relief steel arch assembly 2 comprises:

[0096] S201, weld a plurality of elliptical metal rings 202 on the side of each steel arch 201 close to the rock stratum surface (i.e. on the radially outward side wall), so that the elliptical metal rings 202 are in abutment with the first concrete layer 1; the radial thickness and spacing of the elliptical metal rings 202 can be determined according to the actual situation of the construction site; preferably, the spacing between adjacent elliptical metal rings 202 is less than 50 cm along the circumferential direction of the tunnel;

[0097] S202、prepare several compression rings 204, and weld a sleeve 206 on the outer wall of each compression ring 204, so that the axis of the sleeve 206 is perpendicular to the axis of the compression ring 204;

[0098] S203、prepare several connecting ribs 203, and pass each connecting rib 203 through a sleeve 206;

[0099] S204、weld the two ends of each connecting rib 203 to the adjacent two steel arches 201 respectively; preferably, the distance between the adjacent connecting ribs 203 is less than 50 cm along the circumference of the tunnel;

[0100] S205、rotate each compression ring 204 to adjust its orientation, so that the axis of each compression ring 204 is directed towards the radial direction of the tunnel; when the orientation of the compression ring 204 is adjusted to the right position, press the small-diameter end 208 inward, so that the T-shaped buckle moves inward as a whole, until the positioning spring 211 enters the corresponding second positioning groove 210, thereby achieving temporary positioning of the compression ring 204.

[0101] Embodiment 5:

[0102] On the basis of any of the above embodiments, the EPS concrete comprises the following components:

[0103] portland cement, 200-250 kg / m³;

[0104] EPS (expanded polystyrene) particles with a particle size of 5-8 mm, 6-10 kg / m³;

[0105] rubber particles with a particle size of 1-3 mm, 20-50 kg / m³;

[0106] flexible acrylate, 25-40 kg / m³;

[0107] polypropylene fibers with a length of 12-18 mm, 1.5-2.5 kg / m³;

[0108] concrete air entraining agent, 0.1-0.3 kg / m³;

[0109] silane coupling agent, appropriate amount, used to ensure strong adhesion between the EPS particles and the matrix, and prevent premature failure of the interface.

[0110] Compared with the traditional EPS concrete, the cement consumption is reduced, the flexible acrylate is used to supplement the matrix material, which is beneficial to form a flexible three-dimensional network after curing and improve the ductility. Moreover, the EPS particles and rubber particles form a two-stage flexible aggregate, in which: the large-diameter EPS particles are used to provide macroscopic compression deformation space and improve the energy dissipation effect; and the high content of rubber particles can significantly increase the toughness of the compression concrete layer, which is also beneficial to improve the energy dissipation level. In addition, the polypropylene fiber is used to prevent the cracks in the internal concrete after curing from penetrating through, thereby improving the bearing capacity of the compression concrete layer after stress cracking.

[0111] The EPS concrete provided by the embodiment can be used for the compression concrete layer in the application, and has excellent energy absorption and fault shear effect.

[0112] The above detailed description further describes the purpose, technical scheme and beneficial effects of the present application, and it should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

[0113] It should be noted that, in this document, relational terms such as first and second and the like can only be used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that these entities or operations exist in any such actual relationship or order. Moreover, the terms "comprise", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a list of elements does not only include those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or apparatus. In addition, the term "connected" used in this document, without special description, can be directly connected or indirectly connected via other components.

Claims

1. A composite support structure for tunnels traversing strike-slip faults, characterized in that, The tunnel widening zone is set around the fault; in the tunnel widening zone, a first concrete layer (1), a pressure-relief steel arch assembly (2), a second concrete layer (3), a pressure-relief concrete layer (4), and a secondary lining (5) are set in the radial direction from the outside to the inside. The pressure-relief steel arch frame assembly (2) includes several steel arch frames (201), and several first pressure-relief devices are provided between the steel arch frames (201) and the first concrete layer (1), and several second pressure-relief devices are provided between any two adjacent steel arch frames (201).

2. The composite support structure for tunnels traversing strike-slip faults according to claim 1, characterized in that, The pressure-relief concrete layer (4) is EPS concrete.

3. A composite support structure for tunnels traversing strike-slip faults according to claim 1, characterized in that, The tunnel widening zone is located on the subsidence plate of the fault; and along the tunnel direction: The tunnel widening zone gradually decreases in depth from the end closest to the fault to the end furthest from the fault. The thickness of the pressure-relief concrete layer (4) gradually decreases from the end closest to the fault to the end furthest from the fault. The thicknesses of the first concrete layer (1), the profiled steel arch frame assembly (2), and the second concrete layer (3) remain unchanged.

4. A composite support structure for tunnels traversing strike-slip faults according to claim 1, characterized in that, The first pressure relief device includes a plurality of elliptical metal rings (202) welded to the outer wall of the steel arch frame (201). The cross-section of the elliptical metal rings (202) is elliptical, and the minor axis of the elliptical metal rings (202) extends along the radial direction of the tunnel.

5. A composite support structure for tunnels traversing strike-slip faults according to claim 1, characterized in that, The second pressure relief device includes a plurality of connecting ribs (203) connected between two adjacent steel arch frames (201) and a pressure relief ring (204) connected to the connecting ribs (203).

6. A composite support structure for tunnels traversing strike-slip faults according to claim 5, characterized in that, The cross-section of the pressure relief ring (204) is circular; the axis of the pressure relief ring (204) is perpendicular to the axis of the corresponding connecting rib (203).

7. A composite support structure for tunnels traversing strike-slip faults according to claim 5, characterized in that, The pressure relief ring (204) is made of steel or rubber.

8. A composite support structure for tunnels traversing strike-slip faults according to claim 5, characterized in that, Between two adjacent steel arch frames (201), two adjacent connecting bars (203) are arranged alternately: one connecting bar (203) is connected to the outer diameter end of the two adjacent steel arch frames (201), and the other connecting bar (203) is connected to the inner diameter end of the two adjacent steel arch frames (201); For the connecting bar (203) connected to the outer diameter end of two adjacent steel arch frames (201), the pressure relief ring (204) on it is located in the direction of the inner diameter side of the connecting bar (203); For the connecting rib (203) connected to the inner diameter end of two adjacent steel arch frames (201), the pressure relief ring (204) on it is located on the outer diameter side of the connecting rib (203).

9. A composite support structure for tunnels traversing strike-slip faults according to claim 1, characterized in that, Foam board (205) is also filled between the outer diameter ends of two adjacent steel arch frames (201), and the second pressure relief device is located on the inner side of the foam board (205).

10. A construction method for a composite support structure for tunnels traversing strike-slip faults, based on any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Excavate the tunnel according to the original design outline, and widen the tunnel when it passes through the fracture zone of the strike-slip fault to obtain the tunnel widening zone. S2. The first concrete layer (1) is sprayed onto the rock surface of the tunnel widening area. S3. Erect the compression-type steel arch frame assembly (2). S4, Shotcrete second layer (3); S5. Construct a pressure-relief concrete layer (4); S6. Pouring the secondary lining (5).

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