Large-section tunnel excavation supporting system crossing fault fracture zone

Abstract

The invention discloses a large-section tunnel excavation supporting system crossing a fault fracture zone, which comprises a plurality of self-propelled advanced large pipe sheds arranged on a tunnel vault before excavation and a plurality of advanced small pipes arranged on a tunnel side wall, after excavation of each layer is completed, steel-like fiber concrete is preliminarily sprayed on the top arch and the side wall of the corresponding excavation face, system anchor rods are constructed, then multiple steel supports are arranged on the top arch and the side wall of the corresponding excavation face in the longitudinal direction of the tunnel, and a plurality of cover-weight-free consolidation grouting holes are evenly formed in the top arch and the side wall of the whole section for grouting; and then a plurality of system anchor rods and drainage systems are evenly arranged on the top arch and the side wall of the excavation face, then reinforcing meshes are arranged between the steel supports, and then secondary injection of imitated steel fiber concrete is conducted. The problems that in the prior art, when a tunnel crosses a fault fracture zone, roof fall and collapse accidents are prone to occurring through common excavation supporting measures, and the construction safety and the project progress are seriously affected are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel excavation and support, and relates to a large-section tunnel excavation and support system that crosses a fault fracture zone. Background Art

[0002] With the rapid development of economy, infrastructure construction has been rapidly developed, and a large number of hydraulic tunnels and traffic tunnels have been newly built. It is very common for tunnels to cross fault fracture zones. The rock integrity and strength of fault fracture zones are poor. When tunnels cross fault fracture zones, ordinary excavation support measures are prone to accidents such as roof collapse and collapse, which seriously affect construction safety and project progress. Summary of the invention

[0003] The purpose of the present invention is to provide a large-section tunnel excavation support system that crosses a fault fracture zone, which solves the problem in the prior art that when the tunnel crosses a fault fracture zone, ordinary excavation support measures are prone to roof caving and collapse accidents, seriously affecting construction safety and project progress.

[0004] The technical scheme adopted by the present invention is a large-section tunnel excavation support system across the fault fracture zone, including a plurality of self-propelled advanced large pipe racks set at the arch top and arch foot of the tunnel before excavation and a plurality of advanced small pipes set at the side wall of the tunnel. When excavating the tunnel, step-type layered excavation is adopted, and the bottom of each layer is in the form of an inverted arch. After each layer is excavated: the top arch and side wall of the corresponding excavation surface are initially sprayed with imitation steel fiber concrete and system anchor rods are applied, and then the top arch and side wall of the corresponding excavation surface are Multiple steel supports are set on the wall along the longitudinal direction of the tunnel, and then multiple consolidation grouting holes are evenly set on the top arch and side walls of the corresponding excavation surface for uncovered consolidation grouting. After the grouting is completed, the drainage system is evenly arranged on the top arch and side walls of the excavation surface, and then the steel mesh is arranged between the steel supports, and finally the secondary spraying of imitation steel fiber concrete is carried out; among them, after the excavation of the last layer of the tunnel is completed, when the uncovered consolidation grouting is carried out, uncovered consolidation grouting holes are set on the top arch, side wall and bottom of the corresponding full-section.

[0005] The present invention is also characterized in that:

[0006] The self-propelled large pipe shed is arranged in a circular pattern on the tunnel top arch with a circular spacing of 30 cm. The arrangement direction of the self-propelled large pipe shed is 2° to 4° outward from the tunnel axis.

[0007] The self-advanced large pipe shed is a flower pipe processed from hot-rolled seamless steel pipe. The wall of the self-advanced large pipe shed is evenly arranged with multiple rows of grouting holes along its length, with a row spacing of 15 cm. Two grouting holes are evenly arranged in each row, and the grouting holes in two adjacent rows are staggered. The end of the self-advanced large pipe shed is conical.

[0008] It also includes a pipe rack arch for the tunnel entrance, which is used for positioning and orienting the self-propelled large pipe rack, including multiple arch steel supports set in front of the heading, the arch steel supports are connected by longitudinal steel bars, and multiple rows of arch steel supports are jointly fixedly connected with pipe rack guide pipes, which are welded to the arch steel supports through multiple guide pipe fixing steel bars. When installing the pipe rack guide pipes, the lifting amount and elevation angle are reserved according to the installation requirements of the self-propelled large pipe rack.

[0009] Before the construction of the self-propelled large pipe shed, the pipe shed arch is constructed according to the requirements, and then the pipe shed arch is backfilled with sprayed concrete;

[0010] Before constructing the pipe shed arch, in order to prevent the pipe shed arch from encroaching on the cross-sectional dimensions of the secondary lining concrete of the tunnel and to meet the space requirements for the pipe shed construction equipment, the 5m to 6m area in front of the heading was expanded and the system support of the expanded section was completed before the pipe shed arch construction was carried out;

[0011] When the self-propelled advanced large pipe rack is extended, the joints should be made of steel pipe clamps of equal wall thickness and fully threaded. The joints should be staggered in the cross section. The number of joints in the same cross section of the tunnel longitudinal direction should not exceed 50%, and the joints of adjacent steel pipes should be staggered by at least 0.5m.

[0012] Before the self-propelled advanced large pipe shed grouting, the tunnel face is sealed by spraying nano-imitation steel fiber concrete;

[0013] When grouting with self-propelled advanced large pipe rack, the grouting pressure is 0.5~1.5MPa.

[0014] The advance small conduit is a decorative pipe made of steel pipe. Multiple rows of grouting holes a are evenly arranged on the wall of the advance small conduit along its length. The row spacing is 10cm~20cm. Two grouting holes a are evenly arranged in each row. The grouting holes a in two adjacent rows are staggered. The end of the advance small conduit is tapered. The advance small conduits are evenly arranged along the side walls of the tunnel. The spacing between adjacent advance small conduits is 30cm~40cm. The overlap length between the advance small conduits is not less than 1.5m, and the direction of the advance small conduit is at an angle of 5°~10° with the axis of the tunnel.

[0015] When the tunnel is excavated in steps and layers, after the upper layer is excavated and supported, the surrounding rock will be stabilized before excavating layer by layer to the designed section. The distance before and after the layer excavation shall not be less than 30m, and the bottom of each layer shall be in the form of an inverted arch.

[0016] The thickness of the initial sprayed imitation steel fiber concrete is 5cm. The compressive strength is not less than 12Mpa 8h after spraying, and the compressive strength is not less than 25Mpa 24h. The thickness of the secondary spraying is 20cm.

[0017] The system anchor rods are made of hot-rolled grade III steel bars and are full-length cement mortar-filled anchor rods. They are arranged on the top arch and side walls of the excavation surface. The diameter, length and spacing of the anchor rods can be adjusted according to actual conditions.

[0018] The steel supports are made of hot-rolled ordinary I-beams. The spacing between two adjacent rows of steel supports is no more than 1.5m. Two adjacent steel supports are connected by multiple evenly arranged longitudinal steel bars a. The spacing between two adjacent longitudinal steel bars a is 0.5-1.0m.

[0019] When carrying out layered excavation, the feet of the steel supports erected after each layer of excavation is completed are equipped with connecting channel steels distributed along the longitudinal direction of the tunnel. The feet of the steel supports are welded and fixed to the connecting channel steels. A number of locking anchor rods are evenly arranged at the positions corresponding to the top arch and side walls of the steel supports. The exposed ends of the locking anchor rods are bent and connected to the steel supports and welded and fixed to the steel supports. Two bundles of locking anchor piles are also arranged at the feet of the steel supports after each layer of excavation is completed.

[0020] The drainage system includes multiple drainage holes evenly arranged on the top arch and side walls of the excavation surface, soft permeable pipes arranged around the top arch and side walls of the excavation surface, and drainage ditches set up at the bottom of the tunnel near the two side walls. Water seeping from the rock wall flows from the drainage holes to the soft permeable pipes, and both ends of the soft permeable pipes are connected to the drainage ditches on the corresponding side through drainage hard pipes.

[0021] The beneficial effects of the present invention are:

[0022] The invention is a large-section tunnel excavation support system that crosses the fault fracture zone. The self-propelled advanced large pipe rack and the pipe rack sleeve arch form a beam structure, which can effectively inhibit the loosening and collapse of the surrounding rock, and consolidate the loose rock mass through grouting, thereby improving the physical and mechanical properties of the weak surrounding rock and enhancing the self-bearing capacity of the surrounding rock; the advanced small pipe can reinforce the loose rock layer, and the stability of the loose and weak surrounding rock is enhanced after grouting; the stepped layered excavation can reduce the disturbance caused to the tunnel surrounding rock and reduce the damage to the original soil layer; the setting of the invert arch can release the rock layer stress, reduce the local surrounding rock pressure, avoid the sudden instability of the surrounding rock, and effectively prevent the overall destruction of the surrounding rock; imitation steel fiber sprayed concrete is used as a new The type material can quickly reach the design value of its compressive strength after construction, and can effectively support the surrounding rock in combination with the steel mesh to prevent the surrounding rock from loosening; the steel support can limit the deformation of the surrounding rock, bear part of the relaxation load, and serve as an advance support fulcrum to prevent the surrounding rock from loosening; the consolidation grouting can improve the integrity and strength of the rock mass and reduce the deformation of the rock mass; the system anchor can limit the deformation of the surrounding rock and reinforce the surrounding rock; the drainage system introduces the fissure water of the surrounding rock into the tunnel, reduces the groundwater pressure, and avoids the surrounding rock and subsequent lining structure being damaged by the pressure of the groundwater. In summary, the excavation support system of the present invention can effectively cope with the support needs of large-section tunnels across the fault fracture zone, and ensure the construction safety and project progress. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is an overall elevation view of the large-section tunnel excavation support system across the fault fracture zone of the present invention;

[0024] Figure 2 It is an elevation view of a pipe-roof sleeve arch in a large-section tunnel excavation support system across a fault fracture zone of the present invention;

[0025] Figure 3 yes Figure 2 Middle AA section;

[0026] Figure 4 It is a structural diagram of a self-propelled advanced large pipe shed in a large-section tunnel excavation support system across a fault fracture zone of the present invention;

[0027] Figure 5 It is a structural diagram of the small advance guide tube in the large-section tunnel excavation support system across the fault fracture zone of the present invention;

[0028] Figure 6 It is an elevation view of the steel support in the large-section tunnel excavation support system across the fault fracture zone of the present invention.

[0029] In the figure: 1. Excavation face; 2. Self-propelled large pipe shed; 3. Small pipe shed; 4. Invert; 5. Sprayed steel fiber concrete; 6. Steel support; 7. Locking anchor pile; 8. Uncovered heavy consolidation grouting hole; 9. System anchor rod; 10. Drainage system hole; 11. Soft permeable pipe; 12. Drainage hard pipe; 13. Drainage ditch; 14. Secondary lining concrete; 15. Layered excavation boundary; 16. Pipe shed arch; 17. Sprayed concrete; 18. Arch steel support; 19. Longitudinal steel bar; 20. Pipe shed guide pipe; 21. Guide pipe fixing steel bar; 22. Head face; 23. Grouting hole; 24. Grouting hole a; 25. Locking anchor rod; 26. Connecting channel steel; 27. Longitudinal steel bar a. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] The invention provides a large-section tunnel excavation support system across a fault fracture zone, and its structure is as follows: Figure 1As shown, it includes multiple self-propelled advanced large pipe racks 2 set on the tunnel arch before excavation and multiple advanced small pipes 3 set on the tunnel side walls. When excavating the tunnel, step-by-step layered excavation is adopted, and the bottom of each layer is in the form of an inverted arch 4. After each layer is excavated: the top arch and side wall of the corresponding excavation surface 1 are initially sprayed with imitation steel fiber concrete and system anchor rods 9 are applied, and then multiple steel supports 6 are set on the top arch and side wall of the corresponding excavation surface 1 along the longitudinal direction of the tunnel, and multiple uncovered weight consolidation grouting holes 8 are evenly set on the top arch and side wall of the excavation surface 1 for uncovered weight consolidation grouting. After the grouting is completed, a drainage system is evenly arranged on the top arch and side wall of the excavation surface 1, and then steel mesh is arranged between the steel supports, and then the imitation steel fiber concrete is secondary sprayed; wherein, after the excavation of the last layer of the tunnel is completed, when the uncovered weight consolidation grouting is carried out, the corresponding full-section top arch, side wall and bottom are all provided with uncovered weight consolidation grouting holes 8.

[0033] The present invention uses a self-propelled advance large pipe rack 2 and an advance small guide tube 3 to carry out advance support for the tunnel before excavation, adopts stepped layered excavation to reduce the disturbance to the tunnel surrounding rock, sprays imitation steel fiber sprayed concrete 5 on the excavation surface 1 to quickly seal the rock surface, cooperates with subsequent steel support 6 and steel mesh to form a steel support surrounding rock support structure, and uses system anchor rods 9 and uncovered weight consolidation grouting holes 8 to reinforce the surrounding rock by uncovered weight consolidation grouting to improve the integrity and strength of the rock mass, and uses system drainage to lower the groundwater level. It can effectively meet the support needs of large-section tunnels across fault fracture zones, prevent the collapse of broken surrounding rocks, and ensure construction safety and project progress.

[0034] Example 2

[0035] On the basis of Example 1, Figure 1-3 and Figure 4 As shown, the self-propelled large pipe shed 2 is arranged in a circumferential direction on the tunnel top arch, and the circumferential spacing is 30 cm. The arrangement direction of the self-propelled large pipe shed 2 is in the direction of the tunnel axis tilted outward by 2° to 4°. The flower pipe processed by hot-rolled seamless steel pipe has multiple rows of self-propelled advanced large pipe shed 2 evenly arranged along its length. The grouting holes 23 are arranged at a row spacing of 15 cm, two grouting holes 23 are evenly arranged in each row, and the grouting holes 23 in two adjacent rows are staggered. The end of the self-propelled advanced large pipe shed 2 is conical, which is convenient for drilling. A steel bar bundle is added in the seamless steel pipe to improve the strength of the pipe shed.

[0036] The support system also includes a pipe shed arch 16 for the tunnel entrance. The pipe shed arch 16 is used for positioning and orienting the self-propelled advanced large pipe shed 2. Before constructing the pipe shed arch 16, in order to prevent the pipe shed arch 16 from encroaching on the cross-sectional size of the tunnel secondary lining concrete 14 and to meet the space requirements of the pipe shed construction equipment, the 5m to 6m range in front of the heading face 22 is expanded and the system support of the expanded section is completed before the pipe shed arch 16 is constructed; the pipe shed arch 16 includes setting Multiple arch steel supports 18 are provided, and two adjacent arch steel supports 18 are connected by longitudinal steel bars 19. Multiple arch steel supports 18 are fixedly connected with pipe shed guide pipes 20. The pipe shed guide pipes 20 are welded to the arch steel supports 18 through multiple guide pipe fixing steel bars 21. When installing the pipe shed guide pipes 20, the lifting amount and elevation angle are reserved according to the installation requirements of the self-propelled advanced large pipe shed 2, and the hole direction is ensured to be correct, and then the pipe shed arch 16 is backfilled with sprayed concrete 17;

[0037] When the self-propelled advanced large pipe shed 2 is extended, the joints shall be made of steel pipe clamps of equal wall thickness, fully threaded, and the joints shall be staggered in the cross section. The number of joints in the same cross section in the longitudinal direction of the tunnel shall not exceed 50%, and the joints of adjacent steel pipes shall be staggered by at least 0.5m;

[0038] In order to avoid collapse of the tunnel face 22 due to excessive pressure during the pipe shed grouting process, nano-imitation steel fiber concrete is sprayed on the tunnel face 22 for sealing before the self-propelled advanced large pipe shed 2 grouting;

[0039] When grouting the self-propelled advanced large pipe shed 2, the grouting pressure is 0.5~1.5MPa, the slurry ratio is prepared at 0.5:1, and the final grouting parameters are determined by the on-site grouting test.

[0040] Example 3

[0041] On the basis of Example 2, Figure 1 and Figure 5 As shown, the advanced small catheter 3 is adopted The flower tube is processed by the steel pipe, and the wall of the leading small conduit 3 is evenly arranged with multiple rows along its length. The grouting holes a24 have a row spacing of 10cm to 20cm, two grouting holes a24 are evenly arranged in each row, and the grouting holes a24 in two adjacent rows are staggered. The end of the advance small duct 3 is tapered, and the advance small duct 3 is evenly arranged along the side wall of the tunnel. The spacing between adjacent advance small ducts 3 is 30cm to 40cm, the overlap length between the advance small ducts 3 is not less than 1.5m, and the direction of the advance small duct 3 is at an angle of 5° to 10° with the axis of the tunnel.

[0042] Example 4

[0043] On the basis of Example 1, Figure 1 , Figure 2As shown, when the tunnel is excavated in steps and layers, after the upper layer is excavated and supported, the surrounding rock is stabilized before excavating layer by layer to the designed section. The distance before and after the layer excavation shall not be less than 30m, and the bottom of each layer shall be in the form of an invert 4.

[0044] like Figure 1 and Figure 2 As shown, after the excavation is completed, the excavation surface 1 needs to be sprayed with imitation steel fiber sprayed concrete and a system anchor rod 9 needs to be installed. In order to meet the high-performance early strength requirements of the imitation steel fiber sprayed concrete, nano-grade special admixtures must be added to the initial sprayed concrete. The admixture dosage should be determined through experiments based on the manufacturer's requirements, and the admixture performance indicators should meet the requirements of relevant national and industry specifications; nano-imitation steel fiber concrete should be forcedly mixed, and the mixing process should ensure that the imitation steel fiber is evenly dispersed in the mixture without agglomeration.

[0045] The spraying operation should be carried out in layers. The thickness of the initial sprayed imitation steel fiber concrete is 5cm. The compressive strength after spraying shall not be less than 12Mpa 8h and the compressive strength shall not be less than 25Mpa 24h.

[0046] The system anchor rod 9 is a full-length cement mortar-injected anchor rod made of hot-rolled grade III steel bars, and is systematically arranged on the excavation surface 1 according to the actual situation;

[0047] Example 5

[0048] On the basis of Example 1, Figure 6 As shown, the steel support 6 is made of hot-rolled ordinary I-beam, the distance between two adjacent steel supports 6 is no more than 1.5m, and the two adjacent steel supports 6 are connected by a plurality of evenly arranged longitudinal steel bars a27, and the distance between two adjacent longitudinal steel bars a27 is 0.5-1.0m;

[0049] When carrying out layered excavation, the foot of the steel support 6 set after each layer of excavation is completed is provided with connecting channel steels 26 distributed along the longitudinal direction of the tunnel along the layered excavation boundary line 15, the foot of the steel support 6 is welded and fixed to the connecting channel steel 26, and a plurality of locking anchor rods 25 are evenly arranged at the corresponding top arch and side wall positions on the steel support 6, the exposed ends of the locking anchor rods 25 are bent and connected to the steel support 6 and welded and fixed to the steel support 6, and two bundles of locking foot anchor piles 7 are also arranged at the foot of the steel support 6 after each layer of excavation is completed along the layered excavation boundary line 15. In order to control the lateral deformation of the supporting part of the steel support 6, the construction quality of the foot locking foot anchor rods should be strictly controlled on site, and the number of locking foot anchor rods at the lower part of the side wall should be increased in time when necessary.

[0050] Example 6

[0051] On the basis of Example 5, the uncapped weight consolidation grouting holes 8 are arranged in the whole section, and the grouting pressure should be determined according to the on-site grouting test, and it is required to increase the grouting pressure as much as possible;

[0052] The drainage system includes a plurality of drainage holes 10 evenly arranged on the top arch and side walls of the excavation face 1, a soft permeable pipe 11 arranged around the top arch and side walls of the excavation face 1, and a drainage ditch 13 set at the bottom of the tunnel near the two side walls. Water seeping from the rock wall flows from the drainage holes 10 to the soft permeable pipe 11, and both ends of the soft permeable pipe 11 are respectively connected to the drainage ditch 13 on the corresponding side through a drainage hard pipe 12.

[0053] The rock wall seepage flows from the drainage holes 10 to the soft permeable pipes 11 and the drainage hard pipes 12, and finally to the permanent drainage ditch 13 of the tunnel. When setting the drainage holes 10, the drainage holes 10 are randomly increased in the areas with large water seepage. In order to avoid affecting the permanent drainage effect of the tunnel, the system drainage should be carried out after the uncapped consolidation grouting is completed.

[0054] After that, steel mesh is laid between the steel supports, and finally a secondary spraying of imitation steel fiber concrete is carried out.

[0055] The present invention uses a self-propelled advance large pipe shed 2, an advance small guide tube 3 and a small guide tube to carry out advance support for the tunnel before excavation, adopts stepped layered excavation to reduce the disturbance to the tunnel surrounding rock, sprays imitation steel fiber sprayed concrete on the excavation surface to quickly seal the rock surface, cooperates with subsequent steel supports and steel mesh to form a steel support surrounding rock support structure, reinforces the surrounding rock through uncovered consolidation grouting and system anchor rods to improve the integrity and strength of the rock mass, and uses system drainage to lower the groundwater level. Therefore, the present invention can effectively respond to the support needs of large-section tunnels across fault fracture zones through a systematic excavation and support system, prevent the collapse of broken surrounding rocks, and ensure construction safety and project progress.

Claims

1. A large-section tunnel excavation support system that crosses a fault fracture zone, characterized in that: The invention comprises a plurality of self-propelled large pipe sheds (2) arranged on the tunnel arch before excavation and a plurality of small pipe sheds (3) arranged on the tunnel side wall. When excavating the tunnel, step-type layered excavation is adopted, and the bottom of each layer is in the form of an inverted arch (4). After each layer is excavated, imitation steel fiber concrete (5) is initially sprayed on the top arch and side wall of the corresponding excavation surface (1) and a system anchor rod (9) is applied. Then, a plurality of steel supports (6) are arranged on the top arch and side wall of the corresponding excavation surface (1) along the longitudinal direction of the tunnel. ), a plurality of uncovered weight consolidation grouting holes (8) are evenly arranged on the top arch and side walls of the excavation surface (1) for uncovered weight consolidation grouting. After the grouting is completed, a drainage system is arranged on the top arch and side walls of the excavation surface (1), and then a steel mesh is arranged between the steel supports (6), and then a secondary injection of imitation steel fiber concrete is carried out; wherein, after the excavation of the last layer of the tunnel is completed, when the uncovered weight consolidation grouting is carried out, uncovered weight consolidation grouting holes (8) are arranged on the top arch, side walls and bottom of the corresponding full section.

2. The large-section tunnel excavation support system across the fault fracture zone according to claim 1 is characterized in that: The self-propelled large pipe shed (2) is arranged in a circumferential direction on the tunnel top arch, and the circumferential spacing is 30 cm. The arrangement direction of the self-propelled large pipe shed (2) is in a direction inclined 2° to 4° outward from the tunnel axis.

3. The large-section tunnel excavation support system across the fault fracture zone according to claim 2 is characterized in that: The self-propelled large pipe shed (2) is a flower pipe processed from hot-rolled seamless steel pipe. The pipe wall of the self-propelled large pipe shed (2) is evenly arranged with multiple rows of grouting holes (23) along its length, with a row spacing of 15 cm. Two grouting holes (23) are evenly arranged in each row, and the grouting holes (23) in two adjacent rows are staggered. The end of the self-propelled large pipe shed (2) is conical.

4. The large-section tunnel excavation support system across the fault fracture zone according to claim 3 is characterized in that: It also includes a pipe rack arch (16) for a tunnel entrance, the pipe rack arch (16) is used for positioning and orienting a self-propelled large pipe rack (2), and includes a plurality of arch steel supports (18) arranged on the tunnel entrance surface, two adjacent arch steel supports (18) are connected by longitudinal steel bars (19), and the plurality of arch steel supports (18) are commonly fixedly connected with a pipe rack guide pipe (20), the pipe rack guide pipe (20) is welded to the arch steel support (18) by a plurality of guide pipe fixing steel bars (21), and when the pipe rack guide pipe (20) is installed, a lifting amount and elevation angle are reserved according to the installation requirements of the self-propelled large pipe rack (2).

5. The large-section tunnel excavation support system across the fault fracture zone according to claim 4 is characterized in that: Before the construction of the self-propelled advanced large pipe shed (2), the pipe shed arch (16) is first constructed according to the requirements, and then the pipe shed arch (16) is backfilled with sprayed concrete (17); Before constructing the pipe shed arch (16), in order to prevent the pipe shed arch (16) from encroaching on the cross-sectional size of the secondary lining concrete of the tunnel and to meet the space requirements of the pipe shed construction equipment, the area 5m to 6m in front of the heading face (22) is expanded and the system support of the expanded section is completed, and then the pipe shed arch (16) is constructed; When the self-propelled advanced large pipe shed (2) is extended, the joints shall be made of steel pipe clamps of equal wall thickness and fully threaded. The joints shall be staggered in the cross section. The number of joints in the same cross section in the longitudinal direction of the tunnel shall not exceed 50%. The joints of adjacent steel pipes shall be staggered by at least 0.5m. Before the self-propelled advanced large pipe shed (2) is grouted, nano-imitation steel fiber concrete is sprayed on the tunnel face (22) to seal it; When the self-propelled advanced large pipe shed (2) is grouting, the grouting pressure is 0.5 to 1.5 MPa.

6. The large-section tunnel excavation support system across the fault fracture zone according to claim 5 is characterized in that: The advance small conduit (3) is a flower tube made of steel pipe. The wall of the advance small conduit (3) is evenly provided with multiple rows of grouting holes a (24) along its length, with a row spacing of 10 cm to 20 cm. Two grouting holes a (24) are evenly provided in each row, and the grouting holes a (24) in two adjacent rows are staggered. The end of the advance small conduit (3) is conical. The advance small conduit (3) is evenly arranged along the side wall of the tunnel. The spacing between adjacent advance small conduits (3) is 30 cm to 40 cm. The overlap length between the advance small conduits (3) is not less than 1.5 m. The direction of the advance small conduit (3) is at an angle of 5° to 10° with the tunnel axis.

7. The large-section tunnel excavation support system across the fault fracture zone according to claim 6 is characterized in that: When the tunnel is excavated in steps and layers, after the upper layer is excavated and supported, the surrounding rock is stabilized before excavation is continued layer by layer to the designed section. The distance between the layers shall not be less than 30m, and the bottom of each layer shall be in the form of an invert (4).

8. The large-section tunnel excavation support system across the fault fracture zone according to claim 7 is characterized in that: The thickness of the initially sprayed imitation steel fiber concrete is 5 cm, the compressive strength after spraying is not less than 12 MPa 8 hours later, and the compressive strength after spraying is not less than 25 MPa 24 hours later. The thickness of the secondary spraying is 20 cm.

9. The large-section tunnel excavation support system across the fault fracture zone according to claim 8 is characterized in that: The system anchor rod (9) is a full-length cement mortar-infused anchor rod made of hot-rolled grade III steel bars.

10. The large-section tunnel excavation support system across the fault fracture zone according to claim 9, characterized in that: The steel supports (6) are made of hot-rolled ordinary I-beams, the distance between two adjacent steel supports (6) is no more than 1.5 m, and the two adjacent steel supports (6) are connected by a plurality of evenly arranged longitudinal steel bars a (27), and the distance between adjacent longitudinal steel bars a (27) is 0.5 to 1.0 m; When layered excavation is performed, the foot of the steel support (6) set after each layer of excavation is completed is provided with a connecting channel steel (26) distributed along the longitudinal direction of the tunnel, the foot of the steel support (6) is welded and fixed to the connecting channel steel (26), and a plurality of locking anchor rods (25) are evenly arranged at the positions corresponding to the top arch and the side wall of the steel support (6), the exposed ends of the locking anchor rods (25) are bent and connected to the steel support (6) and welded and fixed to the steel support (6), and two bundles of locking anchor piles (7) are also arranged at the foot of the steel support (6) after each layer of excavation is completed; The drainage system comprises a plurality of drainage holes (10) evenly arranged on the top arch and side walls of the excavation face (1), a soft water-permeable pipe (11) arranged around the top arch and side walls of the excavation face (1), and a drainage ditch (13) arranged at the bottom of the tunnel near the two side walls. Water seeping from the rock wall flows from the drainage holes (10) to the soft water-permeable pipe (11), and both ends of the soft water-permeable pipe (11) are respectively connected to the drainage ditch (13) on the corresponding side through a drainage hard pipe (12).

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