Carbonaceous phyllite soft stratum tunnel structure and its excavation method

Abstract

The application relates to a tunnel structure for carbon phyllite soft stratum, which comprises a tunnel body, wherein the tunnel body is provided with an upper step, a middle step, a lower step and an inverted arch, the upper step, the middle step, the lower step and the inverted arch are sequentially arranged from top to bottom, the cross section of the tunnel body is arched, a mounting groove is arranged in the side wall of the tunnel body at the middle step, the tunnel body is provided with a supporting frame mounted in the mounting groove, the supporting frame is provided with a plurality of first grouting anchor rods, the first grouting anchor rods are distributed along the extension direction of the tunnel body, the first grouting anchor rods are arranged in the supporting frame and anchored in the tunnel body, and the first grouting anchor rods extend downward to the position of the tunnel body at the lower step. The application has the effect of reducing the possibility of collapse in the excavation process.

Description

Technical Field

[0001] This application relates to the field of tunnel construction technology, and in particular to a tunnel structure and excavation method for carbonaceous phyllite soft strata. Background Technology

[0002] In recent years, with the rapid development of highway construction, it is inevitable to encounter tunnel projects with special geological and topographical features, especially tunnel projects in phyllite geology. The tunnel area belongs to the tectonic erosion low mountain landform, and the overall terrain of the area is quite undulating, so there are many cases of shallow burial and bias pressure when the tunnel enters.

[0003] Phyllite is a weak surrounding rock whose main components are quartz, chlorite and sericite. When the water content is high, it is in the form of lumps, and when the water content is low, it is in the form of scales. The foliation is extremely developed, and the joint surfaces feel smooth and have a luster. The rock mass is broken and soft, and the surrounding rock has poor self-stabilizing ability. It is soft in texture, and the original rock softens when it comes into contact with water and has swelling properties.

[0004] For soft rock tunnels, the three-stage, seven-step excavation method is generally chosen. When excavating the side of the lower stage, the initial support of the upper and middle stages is not closed with the initial support of the lower stage. Also, because the excavation location is relatively high from the top of the tunnel, the tunnel sidewall is prone to deformation during the excavation process, which can lead to collapse. Summary of the Invention

[0005] To reduce the possibility of collapse during excavation, this application provides a tunnel structure for soft carbonaceous phyllite strata.

[0006] This application provides a tunnel structure and excavation method for weak carbonaceous phyllite strata, employing the following technical solution:

[0007] A tunnel structure for a weak carbonaceous phyllite stratum includes a tunnel body with an upper step, a middle step, a lower step, and an inverted arch, arranged sequentially from top to bottom. The tunnel body has an arched cross-section. An installation groove is provided on the side wall of the tunnel body at the middle step. The tunnel body is provided with a support frame for installation in the installation groove. The support frame is provided with a plurality of first grouting anchors, which are distributed along the extension direction of the tunnel body. The first grouting anchors pass through the support frame and are anchored to the tunnel body. The first grouting anchors extend downward to the position of the tunnel body at the lower step.

[0008] By adopting the above technical solution, after excavating the middle bench, firstly, an installation trench is excavated on the side wall of the tunnel body located at the middle bench, and a support frame is installed in the installation trench. Then, concrete is sprayed on the side wall of the middle bench for initial support. Next, the first grouting anchor rod is inserted downwards at the bottom of the support frame, and grout is injected into the tunnel body through the first grouting anchor rod. After the grout solidifies in the tunnel, it reduces the softness of the tunnel side wall, thereby reducing the possibility of deformation of the tunnel side wall located at the lower bench during the excavation of the lower bench, which could lead to a collapse.

[0009] Optionally, the upper step, middle step, and lower step are all provided with support structures to support the tunnel body. The support structure located at the middle step is connected to the support frame. A support rod is provided at the middle step. The two ends of the support rod are connected to the support frames on both sides respectively. The support rod is arc-shaped, and the arc opening of the support rod faces upward.

[0010] By adopting the above technical solution, when the deformation inside the tunnel body is detected to be large by the testing instrument, a support rod can be set at the middle step. The two ends of the support rod are connected to the support frames on both sides, so that the support structure, support frame and support rod at the middle step are closed into a ring, thereby improving the support performance of the tunnel body and reducing the deformation of the surrounding rock of the tunnel body sidewall.

[0011] Optionally, the support rod is a telescopic adjustable rod, with both ends of the support rod detachably connected to the support frames on both sides. The two ends of the support rod are slidably connected to a first connecting block in the horizontal direction, and are connected to the support frame through the first connecting block.

[0012] By adopting the above technical solution, the support rod is equipped with a telescopic adjustable rod, so that the length of the support rod can be adjusted, which makes it easier to transport the support rod into the tunnel. At both ends of the support rod, a first connecting block is slidably connected to facilitate fine adjustment of the length of the support rod, and then the two ends of the support rod are connected to the support frames on both sides respectively.

[0013] Optionally, a support rod is provided at the opening of the support frame, and a first mounting block is detachably connected to the support rod. The first mounting block is provided with a positioning rod, and the first connecting block has a positioning hole for the positioning rod to connect to. An elastic ring is provided on the positioning rod, and a tensioning hole for the elastic ring to be tightened is provided at the end of the positioning hole away from the positioning rod. The positioning rod is provided with a first guide surface that forces the elastic ring to expand outward to tighten the inner wall of the tensioning hole. The positioning rod is provided with a driving rod for driving the elastic ring to move closer to the first guide surface.

[0014] By adopting the above technical solution, when installing the support rod, the positioning rod of the first mounting block is locked onto the positioning hole of the first connecting block to position the first connecting block. Then, the elastic ring is driven to move closer to the first guide surface by the drive rod. The first guide surface forces the elastic ring to expand outward and tighten the tension hole to position the first connecting block.

[0015] Optionally, the diameter of the first guide surface gradually increases along the direction close to the positioning rod, the inner ring surface of the elastic ring is adapted to the first guide surface, the drive rod is provided with a pressure block, the pressure block abuts against the side of the elastic ring away from the positioning rod, and the first mounting block is provided with a first elastic element that forces the drive rod to slide.

[0016] By adopting the above technical solution, under normal conditions, the first elastic element drive can force the drive rod to slide, thereby driving the elastic ring to slide in the direction closer to the first guide surface through the pressure block. When the elastic ring slides in the direction closer to the guide block along the first guide surface, the first guide surface opens the inner side of the elastic ring, thereby forcing the elastic ring to deform, making the outer diameter of the elastic ring larger and thus tightening it in the tension hole to fix the first connecting block.

[0017] Optionally, the support structure includes a second grouting anchor rod, with the upper part of the support frame disposed at the first connecting part, and a portion of the second grouting anchor rod passing through the second connecting part and anchored to the tunnel body.

[0018] By adopting the above technical solution, when supporting the tunnel body located at the middle step, the second grouting anchor rod is inserted into the first connection part on the support frame, and then the support structure is installed, so that the support frame and the support structure are integrated, thereby improving the overall integrity and improving the support performance of the tunnel body.

[0019] Optionally, the upper and lower ends of the support frame are connected to the support structures on the middle step and the lower step, respectively.

[0020] By adopting the above technical solution, the support structures of the middle and lower steps are connected by a support frame, thereby improving the integrity between the support structures and enhancing the support performance of the tunnel body.

[0021] A method for tunnel excavation in soft carbonaceous phyllite strata includes the following steps.

[0022] S1: Pre-support is carried out on the upper part of the working face by inserting the upper part of the advanced small guide pipe into the upper part of the working face and then grouting is performed to achieve pre-support.

[0023] S2: Excavate the upper bench. Excavate the working face along the tunnel excavation outline according to the upper bench excavation cycle. At the same time as excavation, build a support structure for the upper bench and pour a concrete layer.

[0024] S3: Excavate the middle bench. Following the tunnel excavation outline, excavate along the middle bench excavation cycle. After excavation, excavate two installation trenches on both sides of the middle bench, with the length of the trenches parallel to the tunnel's length. Install support frames within the trenches, then install the first grouting anchor bolt on the support frame. The first grouting anchor bolt passes through the support frame and is anchored within the surrounding rock. The first grouting anchor bolt is inclined downwards to extend to the height corresponding to the lower bench. Grout is injected into the tunnel body through the first grouting anchor bolt. Then, construct the support structure and pour the concrete layer. S5: Excavate the lower bench and invert arch pits according to the lower bench excavation cycle, simultaneously providing initial support for the lower bench and invert arch until the support structures of each bench and the invert arch form a closed loop.

[0025] S6: Repeat the above steps until the tunnel is completed.

[0026] Optionally, in step S3, before excavating the installation trench, a row of second grouting anchor rods is inserted into the side wall of the middle step above the installation trench. Grouting is then performed on the side wall above the installation trench through the second grouting anchor rods, thereby facilitating the excavation of the installation trench below the second grouting anchor rods.

[0027] By adopting the above technical solution, before excavating the installation trench, a second grouting anchor rod is first inserted above the location where the installation trench needs to be excavated and grout is injected to reduce the softness of the tunnel sidewall, thereby facilitating the excavation of the installation trench.

[0028] In summary, the present invention has the following beneficial effects:

[0029] 1. After excavating the middle bench, firstly, an installation trench is excavated on the side wall of the tunnel body located at the middle bench, and a support frame is installed in the installation trench. Then, concrete is sprayed on the side wall of the middle bench for initial support. Next, the first grouting anchor rod is inserted downward at the bottom of the support frame. Grout is injected into the tunnel body through the first grouting anchor rod. After the grout solidifies in the tunnel, it reduces the softness of the tunnel side wall, thereby reducing the possibility of deformation of the side wall of the tunnel located at the lower bench when excavating the lower bench, which may lead to collapse.

[0030] 2. When the deformation inside the tunnel body is detected to be large by the testing instrument, a support rod can be installed at the middle step. The two ends of the support rod are connected to the support frames on both sides, so that the support structure, support frame and support rod at the middle step are closed into a ring, thereby improving the support performance of the tunnel body and reducing the deformation of the surrounding rock of the tunnel body sidewall. Attached Figure Description

[0031] Figure 1 This is a structural schematic diagram of this embodiment;

[0032] Figure 2This is a schematic diagram of the tunnel body in this embodiment;

[0033] Figure 3 This is a schematic diagram of the telescopic rod in this embodiment;

[0034] Figure 4 This is a schematic diagram showing the connection between the support frame and the telescopic rod in this embodiment;

[0035] Figure 5 This is a schematic diagram of the structure of the fixing block in this embodiment;

[0036] Figure 6 This is a schematic diagram showing the connection between the first connecting block and the first mounting block in this embodiment;

[0037] Figure 7 yes Figure 6 Enlarged view of point A in the middle;

[0038] Figure 8 This is a schematic diagram of the elastic ring in this embodiment.

[0039] In the diagram, 1. Tunnel body; 11. Upper step; 12. Middle step; 13. Lower step; 14. Invert arch; 15. Mounting groove; 2. Support rod; 21. Telescopic rod; 211. First sliding groove; 22. Second connecting block; 221. Sliding rod; 222. Threaded rod; 23. First connecting block; 231. Positioning rod; 232. Sink; 233. Guide block; 234. First guide surface; 235. Sliding block; 236. Second spring; 237. Sliding hole; 23 8. Drive rod; 2381. Pressure block; 239. Pressing plate; 2391. First spring; 24. Elastic ring; 241. Second guide surface; 242. Second sliding groove; 243. First deformation groove; 244. Second deformation groove; 3. Support frame; 31. First connecting part; 311. Third through hole; 32. T-block; 33. Fixing block; 331. T-groove; 34. First mounting block; 341. Positioning hole; 342. Tensioning hole; 4. Support structure; Detailed Implementation

[0040] The following is in conjunction with the appendix Figure 1-8 This application will be described in further detail.

[0041] This application discloses a tunnel structure for soft carbonaceous phyllite strata, referring to... Figure 1 and Figure 2 The tunnel body 1 includes an upper step 11, a middle step 12, a lower step 13, and an invert arch 14. The upper step 11, the middle step 12, the lower step 13, and the invert arch 14 are arranged sequentially from top to bottom. The cross-section of the tunnel body 1 is arched. The upper step 11, the middle step 12, and the lower step 13 are all provided with support structures 4 to support the sidewalls of the tunnel body 1.

[0042] Reference Figure 2 The tunnel body 1 has an installation groove 15 on its side wall at the middle step 12. A support frame 3 is installed in the installation groove 15. During continuous tunnel excavation, several support frames 3 can be installed sequentially along the tunnel's extension direction, allowing them to be assembled together. Each support frame 3 has several first grouting anchors distributed along the extension direction of the tunnel body 1. The bottom wall of the support frame 3 has first through holes corresponding to the first grouting anchors. The first grouting anchors pass through these holes and are anchored to the tunnel body 1. The first grouting anchors extend downwards to the position of the tunnel body 1 at the lower step 13.

[0043] Reference Figure 2 The support structure 4 includes a second grouting anchor, a steel mesh, and a steel arch. After the bench excavation, concrete is first sprayed onto the sidewall of the tunnel body 1 to form initial support. Then, the second grouting anchor is anchored onto the sidewall of the tunnel body 1 and grout is injected into the tunnel body 1. After that, the steel mesh is erected and the steel arch is installed. Finally, a concrete layer is poured for support.

[0044] Referring to the figure, the upper and lower sides of the support frame 3 are both provided with the first connecting part 31. The first connecting part 31 has a third through hole 311. Part of the second grouting anchor rod is inserted through the second connecting part and anchored to the tunnel body 1. The steel mesh of the support structure 4 of the step 12 and the lower step 13 is fixedly connected to the first connecting parts 31 on the upper and lower sides respectively. This makes the support frame 3 and the support structure 4 integrated, thereby improving the overall integrity and enhancing the support performance of the tunnel body 1.

[0045] Reference Figure 2 A support rod 2 is installed at the middle step 12. Both ends of the support rod 2 are detachably connected to the support frames 3 on both sides. The support rod 2 is arc-shaped, with its arc-shaped opening facing upwards. When the deformation inside the tunnel body 1 is detected to be large by the testing instrument, the support rod 2 can be installed at the middle step 12. The two ends of the support rod 2 are connected to the support frames 3 on both sides, thus forming a closed loop with the support structure 4, support frames 3, and support rod 2 at the middle step 12. This improves the support performance of the tunnel body 1 and reduces the deformation of the surrounding rock of the tunnel body 1's sidewalls.

[0046] Reference Figure 2 and Figure 3The support rod 2 is a telescopic adjustable rod, comprising two telescopic rods 21. One telescopic rod 21 has a first sliding groove 211 along its extension direction, and the other telescopic rod 21 is slidably connected to the first sliding groove 211. Multiple sets of second through holes are formed on the telescopic rods 21, and bolts are inserted through these holes to fix the relative positions of the two telescopic rods 21. This allows the length of the support rod 2 to be adjusted, facilitating its transport into the tunnel.

[0047] Reference Figure 4 One end of the telescopic rod 21, away from the other telescopic rod 21, is hinged to a second connecting block 22. The second connecting block 22 is provided with three sliding rods 221 and one threaded rod 222, which are rectangularly distributed on the second connecting block 22. One end of each sliding rod 221 is fixedly connected to the second connecting block 22, and one end of the threaded rod 222 is rotatably connected to the second connecting block 22. Both ends of the support rod 2 are slidably connected to a first connecting block 23 in a direction away from the telescopic rod 21, and are connected to the support frame 3 through the first connecting block 23.

[0048] Reference Figure 4 The first connecting block 23 is slidably connected to the slide rod 221 along the length direction of the slide rod 221. The threaded rod 222 is threadedly connected to the first connecting block 23. By rotating the threaded rod 222, the first connecting block 23 is driven to slide, thereby making the first connecting block 23 move closer to the support frame 3, which facilitates connecting the two ends of the support rod 2 to the support frames 3 on both sides respectively.

[0049] Reference Figure 4 and Figure 5 A fixing block 33 is provided at the opening of the support frame 3. A first mounting block 34 is detachably connected to the fixing block 33. The fixing block 33 protrudes from the side of the support frame 3 at the opening. A T-shaped groove 331 is formed on the upper surface of the fixing block 33 in the vertical direction. A T-shaped block 32 is fixedly connected to the side of the first mounting block 34. When the first mounting block 34 is installed, the T-shaped block 32 slides vertically and connects to the T-shaped groove 331 to realize the installation of the first mounting block 34.

[0050] Reference Figure 6 and Figure 7To securely connect the first connecting block 23 and the first mounting block 34, a positioning rod 231 is provided on the side of the first mounting block 34 away from the T-shaped block 32. The first connecting block 23 has a positioning hole 341 for connecting the positioning rod 231. A limiting member is provided on the positioning rod 231 to limit the movement of the first mounting block 34. The limiting member is an elastic ring 24, and a tensioning hole 342 for tightening the elastic ring 24 is provided at the end of the positioning hole 341 away from the positioning rod 231. The positioning rod 231 has a recessed groove 232 at the end away from the first mounting block 34. The positioning rod 231 is provided with a guide block 233 located in the recessed groove 232. The guide block 233 is coaxially arranged with the positioning rod 231. The outer ring surface of the guide block 233 is the first guide surface 234. The diameter of the first guide surface 234 gradually increases along the direction close to the positioning rod 231. The inner ring surface of the elastic ring 24 is the second guide surface 241 adapted to the first guide surface 234. The positioning rod 231 is provided with a driving rod 238 for driving the elastic ring 24 to move towards the first guide surface 234. The driving rod 238 can force the elastic ring 24 to move towards the guide block 233, thereby expanding the elastic ring 24 outward through the first guide surface 234, causing the elastic ring 24 to deform and tighten in the tensioning hole 342.

[0051] Reference Figure 6 and Figure 7 The guide block 233 is provided with a slider 235 located on the first guide surface 234. The elastic ring 24 is provided with a second sliding groove 242 at the first guide surface 234, and the slider 235 is slidably connected to the second sliding groove 242.

[0052] Reference Figure 8 The end face of the elastic ring 24 has several first deformation grooves 243 extending through it. These first deformation grooves 243 are arranged in a circular array around the axis of the elastic ring 24, extending to the inner ring surface of the elastic ring 24. The end face of the elastic ring 24 also has several second deformation grooves 244 extending through it. These second deformation grooves 244 are arranged in a circular array around the axis of the elastic ring 24, extending to the outer ring surface of the elastic ring 24. By providing the first deformation grooves 243 and the second deformation grooves 244, the elastic ring 24 can be expanded outward.

[0053] Reference Figure 6 and Figure 7A sliding hole 237 is coaxially formed through the end face of the positioning rod 231. One end of the sliding hole 237 extends to the side of the first mounting block 34 away from the first connecting block 23, and the other end extends to the end face of the guide block 233. A drive rod 238 is slidably connected to the sliding hole 237, and one end of the drive rod 238 extends to the side of the first mounting block 34 away from the first connecting block 23. A pressure block 2381 is fixedly connected to the end of the drive rod 238 near the guide block 233. The pressure block 2381 abuts against the end face of the elastic ring 24. The sliding drive rod 238 can force the elastic ring 24 to slide along the guide block 233 through the pressure block 2381, thereby causing the elastic sleeve to deform and tighten the tensioning hole 342.

[0054] Reference Figure 6 and Figure 7 A pressing piece 239 is fixedly connected to the end of the drive rod 238 away from the first connecting block 23. The first mounting block 34 is provided with a first elastic element that forces the drive rod 238 to slide. The first elastic element is a first spring 2391, which is coaxially sleeved on the drive rod 238. One end of the first spring 2391 is fixedly connected to the pressing piece 239, and the other end is fixedly connected to the first mounting block 34. By pressing the pressing piece 239, the drive rod 238 can be driven to slide, thereby limiting the contact of the first connecting block 23. The first spring 2391 can force the drive rod 238 to slide, thereby forcing the elastic ring 24 to deform, thus improving the installation stability of the first connecting block 23.

[0055] Reference Figure 6 and Figure 7 The positioning rod 231 is provided with a second spring 236 that forces the elastic ring 24 to move away from the positioning rod 231. The second spring 236 is located in the sink 232. One end of the second spring 236 is fixedly connected to the positioning rod 231, and the other end of the second spring 236 abuts against the elastic ring 24.

[0056] This embodiment also discloses a method for tunnel excavation in soft carbonaceous phyllite strata, including the following steps:

[0057] S1: Pre-support is provided for the upper part of the working face by inserting the upper part of the advanced small guide pipe into the upper part of the working face and then grouting is performed to achieve pre-support.

[0058] S2: Excavate the upper bench. Excavate the working face along the tunnel excavation outline according to the upper bench excavation cycle. At the same time as excavation, provide initial support for the upper bench until the upper bench of the predetermined length is formed. Then, construct the support structure and pour the concrete layer.

[0059] S3: Excavate the middle bench. Excavate along the tunnel excavation outline according to the middle bench excavation cycle. After excavation, insert a row of second grouting anchors on the side wall above the installation trench of the middle bench. Grout is injected into the side wall above the installation trench through the second grouting anchors. Then, excavate the installation trench below the second grouting anchors. Excavate two installation trenches on both sides of the middle bench. The length direction of the installation trench is parallel to the length direction of the tunnel. Install the support frame in the installation trench. Then, install the first grouting anchor on the support frame. The first grouting anchor passes through the support frame and is anchored in the surrounding rock. The first grouting anchor is inclined downward to extend to the height corresponding to the lower bench. Grout is injected into the tunnel body 1 through the first grouting anchor. Then, build the support structure and pour the concrete layer.

[0060] S5: Excavate the lower bench and invert arch pit according to the lower bench excavation cycle, and at the same time carry out the initial support for the lower bench and invert arch. Then, build the support structure on the lower bench and pour the concrete layer until the initial support structure of each bench and the invert arch are closed into a ring.

[0061] S6: Repeat the above steps until the tunnel is completed.

[0062] The implementation principle of a tunnel structure in a soft carbonaceous phyllite stratum according to an embodiment of this application is as follows: First, after excavating the middle bench 12, an installation groove 15 is excavated on the side wall of the tunnel body 1 located at the middle bench 12, and a support frame 3 is installed in the installation groove 15. Then, concrete is sprayed on the side wall of the middle bench 12 for initial support. Next, a first grouting anchor rod is inserted downward at the bottom of the support frame 3, and grout is injected into the tunnel body 1 through the first grouting anchor rod. After the grout solidifies in the tunnel, it reduces the softness of the tunnel side wall, thereby reducing the possibility of deformation of the side wall of the tunnel located at the lower bench 13 during the excavation of the lower bench 13, which could lead to a collapse.

[0063] When the detection instrument detects that the deformation inside the tunnel body 1 is large, a support rod 2 can be installed at the middle step 12. The two ends of the support rod 2 are connected to the support frames 3 on both sides, so that the support structure 4, support frame 3 and support rod 2 located at the middle step 12 are closed into a ring, thereby improving the support performance of the tunnel body 1 and reducing the deformation of the surrounding rock of the tunnel body 1 sidewall.

[0064] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A carbonaceous phyllite weak ground tunnel structure, characterized by: The utility model provides a tunnel body (1) is provided with upper step (11), middle step (12), lower step (13) and inverted arch (14), upper step (11), middle step (12), lower step (13) and inverted arch (14) are sequentially arranged from top to bottom, the cross section of tunnel body (1) is arched, the lateral wall of tunnel body (1) at middle step (12) is provided with mounting groove (15), tunnel body (1) is provided with the support frame (3) of mounting in mounting groove (15), support frame (3) is provided with a plurality of first grouting anchor rods, a plurality of first grouting anchor rods are distributed along the extension direction of tunnel body (1), first grouting anchor rod is arranged in support frame (3) and is anchored in tunnel body (1), and first grouting anchor rod extends downward to the position of tunnel body (1) at lower step (13); Upper step (11), middle step (12) and lower step (13) are provided with support structure (4) for supporting tunnel body (1), support structure (4) at middle step (12) is connected with support frame (3), support rod (2) is arranged at middle step (12), both ends of support rod (2) are connected with both sides support frame (3) respectively, support rod (2) is arc-shaped, and the arc-shaped opening of support rod (2) faces upwards; Support rod (2) is telescopic adjusting rod, both ends of support rod (2) are detachably connected with both sides support frame (3), and both ends of support rod (2) are slidably connected with first connecting block (23) along horizontal direction, and first connecting block (23) is connected with support frame (3) through first connecting block (23); The opening of support frame (3) is provided with fixed block (33), first mounting block (34) is detachably connected on fixed block (33), first mounting block (34) is provided with positioning rod (231), first connecting block (23) is provided with positioning hole (341) for connecting positioning rod (231), positioning rod (231) is provided with elastic ring (24), the end of positioning hole (341) away from positioning rod (231) is provided with tensioning hole (342) for tensioning elastic ring (24), positioning rod (231) is provided with first guide surface (234) for forcing elastic ring (24) to outwardly expand to tension the inner wall of tensioning hole (342), and positioning rod (231) is provided with driving rod (238) for driving elastic ring (24) to be close to first guide surface (234).

2. A carbonaceous phyllite soft ground tunnel structure according to claim 1, characterised in that: The diameter of first guide surface (234) gradually increases along the direction close to positioning rod (231), the inner ring surface of elastic ring (24) is matched with first guide surface (234), driving rod (238) is provided with pressing block (2381), pressing block (2381) abuts the side surface of elastic ring (24) away from positioning rod (231), and first mounting block (34) is provided with first elastic member for forcing driving rod (238) to slide.

3. A carbonaceous phyllite soft ground tunnel structure according to claim 1, characterized by: The supporting structure (4) comprises second grouting anchor rods, the upper part of the support frame (3) is arranged at the first connecting part (31), and part of the second grouting anchor rods are arranged in the second connecting part and anchored in the tunnel body (1).

4. A carbonaceous phyllite soft ground tunnel structure according to claim 3, characterised in that: The upper and lower ends of the support frame (3) are connected with the supporting structures (4) on the middle step (12) and the lower step (13) respectively.

5. A method of excavating a carbonaceous phyllite weak ground tunnel structure according to claim 3, characterized by: The method comprises the following steps, S1: pre-supporting the upper part of the working face, inserting the upper part of the advance small pipe into the upper part of the working face, and then grouting to realize pre-supporting; S2: excavating the upper step (11), digging the working face along the excavation contour line of the tunnel according to the excavation cycle footage of the upper step (11), and performing primary support on the upper step (11) while digging, then building the supporting structure (4) and pouring the concrete layer; S3: excavating the middle step (12), digging along the excavation contour line of the tunnel according to the excavation cycle footage of the middle step (12), after the excavation is completed, two installation grooves (15) are excavated on the two sides of the middle step (12), the length direction of the installation groove (15) is parallel to the length direction of the tunnel, the support frame (3) is installed in the installation groove (15), then the first grouting anchor rod is installed on the support frame (3), the first grouting anchor rod is arranged in the support frame (3) and anchored in the surrounding rock, the first grouting anchor rod is arranged downwardly and inclinedly to extend to the height corresponding to the lower step (13), and the first grouting anchor rod is used for grouting into the tunnel body (1), then the supporting structure (4) is built and the concrete layer is poured; S5: excavating the lower step (13) and the inverted arch (14) pit according to the excavation cycle footage of the lower step (13), and simultaneously supporting the lower step (13) and the inverted arch (14), then building the supporting structure (4) and pouring the concrete layer, until the supporting structure (4) of each step and the inverted arch (14) are closed to form a ring; S6: repeating the above steps until the tunnel is completed.

6. A method of excavating a tunnel in a carbonaceous phyllite soft ground formation according to claim 5 wherein: In step S3, before the installation groove (15) is excavated, a row of second grouting anchor rods are inserted into the side wall of the middle step (12) above the installation groove (15), the side wall above the installation groove (15) is grouted through the second grouting anchor rods, so that the installation groove (15) is excavated below the second grouting anchor rods.

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