A large-section tunnel surrounding rock supporting system and a supporting method

Abstract

This application relates to the field of tunnel engineering, specifically a large-section tunnel surrounding rock support system. The system includes a flexible support system for releasing ground pressure in the surrounding rock and a rigid support system for final support. After tunnel excavation, the flexible support system is first laid, followed by the rigid support system after it has been formed. The flexible support system includes multiple sets of anchor bolts, a steel mesh, and a steel arch frame. The anchor bolts are also equipped with positioning components for fixing the steel mesh. These positioning components are slidably connected to the anchor bolts and fixedly connected to the steel mesh, and are then reinforced with shotcrete. This application reduces the distance error between the steel mesh and the surrounding rock at different connection points, resulting in more uniform stress on the steel mesh and improved support effectiveness. This application also relates to a method for supporting the surrounding rock of a large-section tunnel, which ensures the overall strength of the flexible support system while increasing the supporting effect of the steel mesh.

Description

Technical Field

[0001] This application relates to the field of tunnel engineering, and in particular to a support system and method for surrounding rock of large-section tunnels. Background Technology

[0002] During tunnel construction, the longitudinal excavation length for each section needs to be determined in advance based on the specific conditions of the rock mass. This means dividing the entire tunnel into multiple tunnel sections for sequential excavation. During construction, the first tunnel section is excavated according to the specified excavation length. Then, support is implemented in this first tunnel section. After completion, the second tunnel section can be excavated longitudinally from the end of the first tunnel section. Support is then implemented in the second tunnel section. After completion, the third tunnel section is excavated longitudinally from the end of the second tunnel section. This process continues until the support construction of the last tunnel section is completed, and the multiple tunnel sections form a complete tunnel.

[0003] Regarding the aforementioned technologies, the inventors believe that the existing support process adopts a method of directly and closely attaching to the surface of the tunnel to establish flexible initial support. In this method, the positioning between the steel mesh and the anchor rod is measured using traditional measurement methods and fixed by welding. This positioning method has large errors, which can easily lead to large distance errors between the steel mesh and the surrounding rock at different connection points, resulting in uneven stress on the steel mesh and affecting the overall support effect. Summary of the Invention

[0004] In order to reduce the distance error between the steel mesh and the surrounding rock at different connection points, make the steel mesh more uniformly stressed, and improve the support effect, this application provides a large-section tunnel surrounding rock support system and support method.

[0005] The large-section tunnel surrounding rock support system provided in this application adopts the following technical solution: A large-section tunnel surrounding rock support system includes a flexible support system for releasing ground pressure in the surrounding rock and a rigid support system for final support. After tunnel excavation, the flexible support system is laid first, and after the flexible support system is formed, the rigid support system is laid. The flexible support system includes multiple sets of anchor bolts, steel mesh, and steel arches. The anchor bolts are also equipped with positioning components for fixing the steel mesh. The positioning components are slidably connected to the anchor bolts and fixedly connected to the steel mesh, and are formed by shotcrete pouring.

[0006] By adopting the above technical solutions, flexible support combined with rigid support constitutes a composite support method. The combined support of anchor bolts, steel mesh, and shotcrete allows for timely trial support, limiting excessive deformation and loosening of the surrounding rock while allowing for a certain degree of deformation. The rigid support, with its rigidity and end-face dimensions, can withstand strong loosening ground pressure to maintain the stability of the surrounding rock. The flexible support utilizes positioning components on the anchor bolts to reduce the distance error between the steel mesh and the rock surface during installation, providing pre-support for the steel mesh, initial positioning, reducing subsequent welding errors, and minimizing distance errors between the steel mesh and the surrounding rock at different connection points. This results in more uniform stress distribution on the steel mesh and improved support effectiveness.

[0007] Optionally, the positioning component includes a positioning sleeve fitted over the outside of the anchor rod and a fixed support for supporting the steel mesh. The positioning sleeve is fixedly connected to the fixed support, and anchor rods are fixedly provided on both sides of the positioning sleeve. The positioning sleeve slides along the anchor rod and changes the distance between the fixed support and the surrounding rock by adjusting the anchoring depth of the anchor rods.

[0008] By adopting the above technical solution, the support part can support the transverse bars of the steel mesh, thereby transferring the weight of the steel mesh to the anchor rod, thus increasing the support effect of the steel mesh on the surrounding rock. The positioning sleeve, which is slidably connected to the anchor rod, can be adjusted in position on the anchor rod, thereby adjusting the support position of the steel mesh and changing the distance between the steel mesh and the surrounding rock surface. The positioning sleeve is fixed by the anchor rod, so that the positioning sleeve will not rotate, and the support strength of the fixed support part is also increased.

[0009] Optionally, the fixed support is tubular, and an opening is provided on the upward-facing side wall of the fixed support for the steel mesh to be inserted.

[0010] By adopting the above technical solution, the tubular fixed support can support the steel mesh from below, thereby increasing the support effect of the fixed support on the steel mesh. At the same time, the opening allows the transverse bars of the steel mesh to be inserted into the inner hole of the fixed support, so that the fixed support can restrict the deformation of the steel mesh in the direction of approaching or moving away from the surrounding rock surface, thereby increasing the stability of the steel mesh.

[0011] Optionally, the positioning sleeve is also slidably provided with a sliding positioning sleeve identical to the fixed support part. The two ends of the sliding positioning sleeve in the length direction are slidably connected to the anchor rod. The anchor rod is threaded with two fixing nuts, and the sliding positioning sleeve is clamped and fixed by the two fixing nuts.

[0012] By adopting the above technical solution, and utilizing a sliding support with the same structure as the fixed support, the sliding support can provide good support for the steel mesh while moving along the length of the positioning sleeve, thereby changing the support position of the steel mesh. This allows the support position of the steel mesh to be adjusted, facilitating the laying and positioning of the steel mesh.

[0013] Optionally, the steel arch frame is made of TH-shaped steel, and the inner side of the steel arch frame is filled with elastic blocks.

[0014] By adopting the above technical solution, when the steel arch frame is deformed under pressure, the elastic blocks generate a force to recover the deformation through their own elasticity, thereby increasing the support effect of the steel arch frame.

[0015] Optionally, multiple trusses are fixedly installed between two adjacent steel arch frames, and the trusses are installed along the extension direction of the steel arch frame.

[0016] By adopting the above technical solution, the top of the truss beam is welded and fixed to the steel mesh located on the outside, thereby increasing the connection strength of the truss beam and the support strength of the steel arch frame.

[0017] Optionally, the rigid support includes a mesh lining and a secondary lining constructed of concrete, wherein the mesh lining is made of welded steel bars and cast inside the secondary lining.

[0018] By adopting the above technical solution, a lining mesh is poured into the secondary lining, which enables the secondary lining to maintain its rigidity while having a certain degree of elasticity, thereby increasing the toughness of the secondary lining and increasing its deformation capacity to a certain extent during the process of heating or pressing.

[0019] Optionally, the lining mesh is fixed with multiple reinforcing bars perpendicular to the rock surface.

[0020] By adopting the above technical solution, the connection area between the lining mesh and the secondary lining can be increased by using rebar anchoring, making the fit between the secondary lining and the lining mesh stronger. At the same time, the rebar anchoring increases the compressive strength of the secondary lining in the direction perpendicular to the rock surface, thereby further improving the strength of the secondary lining.

[0021] This application provides a method for supporting surrounding rock of large-section tunnels, which adopts the following technical solution: A method for supporting surrounding rock of a large-section tunnel, as described above, includes the following specific steps: S1. Anchor bolt installation: Drill anchor holes and install anchor bolts, with the anchor bolts perpendicular to the surrounding rock surface; S2. Installing and positioning the reinforcing mesh: Fix the reinforcing mesh using positioning components and weld it in place; S3. Erecting steel arch frames and trusses: The steel arch frames are perpendicular to the tunnel extension direction, and the trusses are distributed along the extension direction of the steel arch frames; S4. Shotcrete and curing: Wet shotcrete is poured and the curing time is not less than 14 days. S5. Install the lining mesh, pour the secondary lining, and carry out curing.

[0022] By adopting the above technical solution and adding a positioning component for adjusting the steel mesh during the installation process, the overall strength of the flexible support system is ensured while the support effect of the steel mesh is increased, thus enhancing the strength and support effect of the flexible support system.

[0023] In summary, this application includes at least one of the following beneficial technical effects: 1. A composite support method consisting of flexible and rigid support is used. The combined support of anchor bolts, steel mesh, and shotcrete allows for timely trial support, limiting excessive deformation and loosening of the surrounding rock while allowing for a certain degree of deformation. The rigid support, with its rigidity and end-face dimensions, can withstand strong loosening ground pressure to maintain the stability of the surrounding rock. The flexible support utilizes positioning components on the anchor bolts to reduce the distance error between the steel mesh and the rock surface during the laying process, providing pre-support for the steel mesh, initial positioning of the steel mesh, reducing subsequent welding errors, and reducing the distance error between the steel mesh and the surrounding rock at different connection points. This results in more uniform stress on the steel mesh and improved support effectiveness. 2. The tubular fixed support can support the steel mesh from below, thereby increasing the support effect of the fixed support. At the same time, the opening allows the transverse bars of the steel mesh to be inserted into the inner hole of the fixed support, so that the fixed support can restrict the deformation of the steel mesh in the direction of approaching or moving away from the surrounding rock surface, thereby increasing the stability of the steel mesh. 3. By using a sliding support with the same structure as the fixed support, the sliding support can provide good support for the steel mesh while moving along the length of the positioning sleeve, thereby changing the support position of the steel mesh. This allows the support position of the steel mesh to be adjusted, facilitating the laying and positioning of the steel mesh. 4. By adding a positioning component for adjusting the steel mesh during the installation process, the overall strength of the flexible support system is ensured while the support effect of the steel mesh is increased, thus enhancing the strength and support effect of the flexible support system. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of a large-section tunnel surrounding rock support system according to this application.

[0025] Figure 2This is a schematic diagram of the positioning component structure in an embodiment of this application.

[0026] Figure 3 This is a schematic diagram of the steel arch frame structure in an embodiment of this application.

[0027] Figure 4 This is a schematic diagram of the rigid support system structure in the embodiments of this application.

[0028] Explanation of reference numerals in the attached drawings: 1. Flexible support system; 11. Anchor bolt; 12. Reinforcing mesh; 13. Steel arch frame; 131. Elastic block; 132. Truss beam; 14. Shotcrete layer; 2. Rigid support system; 21. Lining mesh; 211. Rebar installation; 22. Secondary lining; 3. Positioning component; 31. Positioning sleeve; 32. Fixed support part; 33. Connecting plate; 34. Anchor bolt; 35. Sliding support part; 36. Fixing nut. Detailed Implementation

[0029] The following is in conjunction with the appendix Figure 1-4 This application will be described in further detail.

[0030] This application discloses a large-section tunnel surrounding rock support system. (Refer to...) Figure 1 The large-section tunnel surrounding rock support system includes a flexible support system 1 and a rigid support system 2. After tunnel excavation, the flexible support system 1 is laid and supported by the surrounding rock. After the flexible support system 1 is formed, the rigid support system 2 is laid. The flexible support system 1 includes multiple sets of anchor bolts 11, steel mesh 12, and steel arch frame 13. The anchor bolts 11 are hollow grouting anchor bolts 11 and are vertically anchored to the surrounding rock surface. A positioning component 3 is fitted on the anchor bolt 11 to position the steel mesh 12. The steel mesh 12 is fixed together by changing the distance between the steel mesh 12 and the surrounding rock surface through the positioning component 3.

[0031] refer to Figure 2 The positioning component 3 includes a positioning sleeve 31 for connecting the anchor rod 11 and a fixed support part 32 for supporting the transverse bars of the steel mesh 12. The fixed support part 32 is fixedly connected to the top end of the positioning sleeve 31 away from the surrounding rock and slides along the axis of the anchor rod 11 with the positioning sleeve 31. The fixed support part 32 is arranged horizontally, and its axis is perpendicular to the axis of the anchor rod 11. A connecting plate 33 is fixedly connected to the bottom end of the fixed support part 32. The surface of the connecting plate 33 is perpendicular to the axis of the positioning sleeve 31, and the fixed support part 32 is fixedly connected to the positioning sleeve 31 through the connecting plate 33. Two anchor rods 34 are fixedly connected to the connecting plate 33. The two anchor rods 34 are located on both sides of the positioning sleeve 31, and their axes are parallel to the axis of the positioning sleeve 31. The positioning sleeve 31 is anchored to the surrounding rock through the anchor rods 34, and the distance between the positioning sleeve 31 and the surrounding rock is changed by changing the depth of the anchor rods 34 in the surrounding rock.

[0032] refer to Figure 2 The top end face of the fixed support part 32 has an opening, which is arranged along the axial direction of the fixed support part 32. The horizontal bars of the steel mesh 12 can be inserted into the fixed support part 32 through the opening and fixedly connected to the fixed support part 32 by welding, thereby fixing the position of the outer steel mesh 12.

[0033] refer to Figure 2 The positioning sleeve 31 is also slidably connected to a sliding support 35 for positioning the inner reinforcing cage. The sliding support 35 is the same as the fixed support 32. The sliding support 35 is slidably connected to the positioning sleeve 31 through a connecting plate 33. Two fixing nuts 36 are threaded onto each of the two anchor rods 34, and the two fixing nuts 36 are located on both sides of the sliding support 35. When the two fixing nuts 36 approach the sliding support 35 along the axial direction of the anchor rod 34, the two fixing nuts 36 press against the connecting plate 33 on the sliding support 35, thereby fixing the sliding support 35 and the positioning sleeve 31 together. The transverse bars on the inner reinforcing mesh 12 are inserted into the sliding support 35 through the opening, and the inner reinforcing mesh 12 is fixed to the sliding support 35 by welding.

[0034] refer to Figure 3 The steel arch frame 13 is made of TH-shaped steel. The V-shaped groove of the steel arch frame 13 is filled with multiple elastic blocks 131, which are fixedly connected to the steel arch frame 13 along its curvature. When the steel arch frame 13 is deformed under pressure, the elastic blocks 131 generate a force to recover the deformation through their own elasticity, thereby increasing the support effect of the steel arch frame 13.

[0035] Multiple trusses 132 are fixedly connected between two adjacent steel arch frames 13, with the length of the trusses 132 aligned with the tunnel's extension direction. One end of each truss 132 is welded to the sidewall of one of the steel arch frames 13, and the other end is welded to the sidewall of the other steel arch frame 13. The multiple trusses 132 are spaced apart along the curvature of the steel arch frames 13. The top of each truss 132 is welded to the outermost reinforcing mesh 12, thereby increasing the connection strength of the trusses 132 and the support strength of the steel arch frames 13.

[0036] refer to Figure 1 The flexible support system 1 also includes a shotcrete layer 14, anchor bolts 11, steel mesh 12, and steel arch frame 13, all of which are poured using shotcrete. Shotcreting is carried out in sections, distributions, and blocks, and curing begins 2 hours after the concrete has fully set, with a curing time of no less than 14 days. After the flexible support system 1 has cured, the rigid support system 2 is constructed.

[0037] refer to Figure 4 The rigid support system 2 includes a mesh lining 21 and a secondary lining 22. The mesh lining 21 is cast inside the secondary lining 22. The mesh lining 21 is made of steel bars welded together horizontally and vertically. After the secondary lining 22 is cast, the mesh lining 21 is located inside the masonry, thereby increasing the strength of the secondary lining 22.

[0038] On the side of the lining mesh 21 away from the surrounding rock, multiple reinforcing bars 211 are welded and fixed. The length direction of the reinforcing bars 211 is perpendicular to the rock surface. One end of the reinforcing bar 211 is fixedly connected to the lining mesh 21 by welding, and the other end of the reinforcing bar 211 extends in the direction away from the surrounding rock and is cast together with the lining mesh 21 into the interior of the secondary lining 22.

[0039] This application also discloses a method for supporting surrounding rock in large-section tunnels. The specific steps are as follows: S1. Anchor bolt 11 installation: Anchor bolt 11 is perpendicular to the contour of the surrounding rock surface. For horizontally layered rock strata, it is arranged perpendicular to the bedding plane or obliquely. S2. Install the steel mesh 12 and position the steel mesh 12: Put the positioning sleeve 31 on the anchor rod 11 and anchor the positioning sleeve 31 to the surrounding rock support through the anchor rod 34. Measure the distance between the fixed support part 32 and the surrounding rock. Adjust the sliding support part 35 to a certain distance from the fixed support part 32. Hang the inner steel mesh 12 on the sliding support part 35 and weld the transverse bars of the steel mesh 12 to the sliding support part 35. Hang the outer steel mesh 12 on the fixed support part 32 and weld the transverse bars of the steel mesh 12 to the fixed support part 32. S3. Erecting the steel arch frame 13 and the truss beam 132: The inner side of the steel arch frame 13 is filled with elastic blocks 131. When erected, it is perpendicular to the centerline of the tunnel. After the arch foot is fixed with concrete, the truss beam 132 is welded. S4. Shotcrete and curing: Shotcrete is applied in layers, from bottom to top, to the required thickness. After the shotcrete has set for 4 hours, water curing is carried out, and the curing time is no less than 14 days. S5. Install the lining mesh 21, pour the secondary lining 22 and carry out curing.

[0040] 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 large-section tunnel surrounding rock support system, characterized in that: The system includes a flexible support system (1) for releasing the ground pressure of the surrounding rock and a rigid support system (2) for final support. After the tunnel is excavated, the flexible support system (1) is laid first. After the flexible support system (1) is formed, the rigid support system (2) is laid. The flexible support system (1) includes multiple sets of anchor rods (11), steel mesh (12) and steel arch frame (13). The anchor rods (11) are also provided with positioning components (3) for fixing the steel mesh (12). The positioning components (3) are slidably connected to the anchor rods (11) and fixedly connected to the steel mesh (12), and are poured with shotcrete. The positioning component (3) includes a positioning sleeve (31) sleeved on the outside of the anchor rod (11) and a fixed support part (32) for supporting the steel mesh (12). The positioning sleeve (31) is fixedly connected to the fixed support part (32). Anchor rods (34) are fixedly provided on both sides of the positioning sleeve (31). The positioning sleeve (31) slides along the anchor rod (11) and changes the distance between the fixed support part (32) and the surrounding rock by the anchoring depth of the anchor rods (34). The positioning sleeve (31) is also slidably provided with a sliding support part (35) that is the same as the fixed support part (32). The two ends of the sliding support part (35) in the length direction are slidably connected to the anchor rod (34). The anchor rod (34) is threaded with two fixing nuts (36). The sliding support part (35) is clamped and fixed by the two fixing nuts (36).

2. The large-section tunnel surrounding rock support system according to claim 1, characterized in that: The fixed support part (32) is tubular, and the fixed support part (32) has an opening on the upward-facing side wall for the steel mesh (12) to be inserted.

3. The large-section tunnel surrounding rock support system according to claim 1, characterized in that: The steel arch frame (13) is made of TH-shaped steel, and the inner side of the steel arch frame (13) is filled with elastic blocks (131).

4. The large-section tunnel surrounding rock support system according to claim 1, characterized in that: Multiple trusses (132) are fixedly installed between two adjacent steel arch frames (13), and the trusses (132) are installed along the extension direction of the steel arch frame (13).

5. The large-section tunnel surrounding rock support system according to claim 1, characterized in that: The rigid support includes a lining mesh (21) and a secondary lining (22) made of concrete. The lining mesh (21) is made of welded steel bars and cast inside the secondary lining (22).

6. The large-section tunnel surrounding rock support system according to claim 5, characterized in that: Multiple reinforcing bars (211) perpendicular to the rock surface are fixed on the lining mesh (21).

7. A support method for a large-section tunnel surrounding rock support system according to any one of claims 1-6, characterized in that: The specific steps are as follows: S1, Anchor bolt (11) installation: Drill anchor holes and install anchor bolts (11), with the anchor bolts (11) perpendicular to the surrounding rock surface; S2. Hang the steel mesh (12) and position the steel mesh (12): use the positioning component (3) to fix the steel mesh (12) and weld it in place; S3. Erecting steel arch frame (13) and truss beam (132): The steel arch frame (13) is perpendicular to the tunnel extension direction, and the truss beam (132) is distributed along the extension direction of the steel arch frame (13); S4. Shotcrete and curing: Wet shotcrete is poured and the curing time is not less than 14 days. S5. Install the lining mesh (21), pour the secondary lining (22) and carry out curing.

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