Active supporting and reinforcing method for tunnel face

Abstract

The invention relates to the technical field of tunnel reinforcement, in particular to an active supporting and reinforcing method for a tunnel face. The reinforcing method comprises the following steps that a tunnel is excavated in stratum surrounding rock with the strain hardening characteristic; after the tunnel is excavated, stability parameters of surrounding rock are monitored in real time; a reinforcing mesh is applied to the tunnel face, and the edge of the reinforcing mesh is connected with the edge of the tunnel face; tightening the reinforcing mesh through a concentrator until the reinforcing mesh is completely tightened, so that the reinforcing mesh actively applies pressure to the tunnel face; and after the surrounding rock reaches the self-stabilization state, the reinforcing mesh is removed, and excavation operation of the next cycle is carried out. According to the reinforcing method, pressure is actively applied to the tunnel face by tightening the reinforcing mesh, so that the fractured rock mass is re-compacted under the combined action of the vertical load and the active pressure, self-healing of the fractured rock mass is achieved, and safety and stability of tunnel construction are guaranteed. According to the reinforcing method, the bearing capacity of the surrounding rock is utilized to the maximum extent, tunnel face supporting work can be reduced, and supporting materials are saved.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel reinforcement, and particularly to an active support and reinforcement method for a tunnel heading face. Background Art

[0002] In current tunnel construction, the support measures after tunnel excavation are important factors to ensure the temporary stability of the tunnel and the smooth progress of subsequent construction. Among them, the support and reinforcement of the tunnel heading face is the key link to ensure the overall stability of the excavated tunnel. Especially in the construction of large-span soft surrounding rock tunnels, due to their complex geological conditions, strong interaction between rock strata, and low strength of rock and soil masses, the heading face is extremely prone to extrusion deformation under the action of longitudinal extrusion pressure, which in turn causes instability of the tunnel surrounding rock and poses a great threat to the overall construction safety of the tunnel.

[0003] To control this deformation, various measures need to be taken during construction to reinforce and restrain the tunnel heading face, weaken the extrusion deformation of the heading face, and maintain the overall safety and stability of the tunnel. The existing extrusion deformation control methods mainly restrain and reinforce the tunnel heading face by leaving a core soil, changing the shape of the heading face, and shotcreting the heading face. For specific control methods, refer to the Chinese invention patents with application numbers 202411457334.1 and 202410937091.5. For large-span soft surrounding rock tunnels, multiple methods are often combined, resulting in complex processes, long construction periods, large material consumption, and low utilization rate of the engineering properties of the rock and soil mass itself, and unable to better exert the self-stabilizing ability of the rock and soil mass. Therefore, it is very necessary to summarize and study a convenient and efficient tunnel heading face support method. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a convenient and efficient active support and reinforcement method for a tunnel heading face.

[0005] To solve the above technical problem, the technical solution adopted by the present invention is: an active support and reinforcement method for a tunnel heading face, comprising the following steps: Excavate a tunnel in the strata surrounding rock with strain hardening characteristics; After the tunnel is excavated, monitor the stability parameters of the surrounding rock in real time; Apply a steel mesh to the tunnel heading face, and connect the edge of the steel mesh to the edge of the tunnel heading face; Tighten the steel mesh through a hub until it is completely taut, so that the steel mesh actively applies pressure to the tunnel heading face; After the stability parameters of the surrounding rock are maintained within the preset threshold parameter range and reach the self-stabilizing state, remove the steel mesh and carry out the excavation operation of the next cycle.

[0006] The beneficial effects of the present invention are as follows: In the active support and reinforcement method for the tunnel face of the present invention, pressure is actively applied to the tunnel face by tightening the steel mesh, so that the fractured rock mass is re-compacted under the combined action of vertical load and active pressure, realizing the self-healing of the fractured rock mass and ensuring the safety and stability of tunnel construction. This reinforcement method maximally utilizes the bearing capacity of the surrounding rock itself, can reduce the support operation of the tunnel face, and save support materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is the construction flow chart of the embodiment of the present invention; Figure 2 is a schematic diagram of the typical stress-strain curve of the strain-hardening characteristic soil sample in the embodiment of the present invention; Figure 3 is a schematic diagram of the active support and reinforcement structure in the embodiment of the present invention; Figure 4 is a schematic diagram of the structure of the steel mesh in the embodiment of the present invention; Figure 5 is a schematic diagram of the connection structure between the steel mesh and the limiting member in the embodiment of the present invention; Label description: 1, tunnel; 2, tunnel face; 3, steel mesh; 4, primary support bolt; 5, limiting member; 6, hub; 7, bolt chute of the locking structure; 8, main reinforcement. DETAILED DESCRIPTION OF THE INVENTION

[0008] In order to describe in detail the technical content, the achieved objectives and the effects of the present invention, the following is described in conjunction with the embodiments and with reference to the drawings.

[0009] Please refer to Figure 1 , an active support and reinforcement method for a tunnel face, comprising the following steps: Excavate a tunnel in the surrounding rock of the formation with strain-hardening characteristics; After the tunnel is excavated, the stability parameters of the surrounding rock are monitored in real time; Apply a steel mesh to the tunnel face, and the edge of the steel mesh is connected to the edge of the tunnel face; Tighten the steel mesh through the hub until it is completely taut, so that the steel mesh actively applies pressure to the tunnel face; After the stability parameters of the surrounding rock are maintained within the preset threshold parameter range and reach the self-stabilized state, remove the steel mesh and carry out the excavation operation of the next cycle.

[0010] Among them, the stability parameters include conventional parameters such as surrounding rock pressure and surface settlement value.

[0011] As can be seen from the above description, the beneficial effects of the present invention are as follows: When performing a conventional triaxial test on a soil sample with strain-hardening characteristics, after shear failure occurs, the two sheared parts of the soil sample can be quickly recompacted into a whole under the confining pressure along the shear fracture surface, and the stress-strain relationship curve reflects that it has a very high post-peak strength. Therefore, it is considered that the rock and soil mass with strain-hardening characteristics has self-healing characteristics after shear failure, and the recompacted rock and soil mass has a rock mass strength and surrounding rock stability close to those before failure.

[0012] The present invention utilizes the self-healing characteristics of the fracture surface after the surrounding rock is strain-hardened, and summarizes an active support and reinforcement method for the tunnel face applicable to complex geological conditions such as weak surrounding rock strata and high fragmentation of the rock mass. Specifically, the present invention provides active support pressure to the tunnel face by applying a steel mesh that has an active support effect on the tunnel face; it can effectively utilize the self-healing characteristics exhibited by the surrounding rock with strain-hardening characteristics, maximize the use of the bearing capacity of the surrounding rock itself, reduce the support operation of the tunnel face, and save support materials; this support and reinforcement method has the advantages of relatively simple operation and low cost, and has less disturbance to the tunnel surrounding rock, which is more conducive to the safety and stability of construction.

[0013] The present invention is a flexible support, and the shape of the steel mesh used can be customized according to the shape of the excavation face, and is applicable to the tunnel excavation of various cross-section forms; the steel mesh can be disassembled after use, and can achieve the effect of repeated use, effectively saving construction resources.

[0014] Please refer to Figure 3 , further, the steel mesh is fixed on the tunnel face through the primary support bolts. One end of the primary support bolt is embedded in the tunnel face, and the other end is connected to the steel mesh.

[0015] As can be seen from the above description, the steel mesh is tightly attached to the tunnel face through the primary support bolts.

[0016] Further, the other end of the primary support bolt is connected to a limiting member, and the steel mesh is detachably connected to the primary support bolt through the limiting member.

[0017] Please refer to Figure 4 , further, the steel mesh includes main steel bars and secondary steel bars. A plurality of main steel bars are arranged radially, and the secondary steel bars are connected to the main steel bars in a ring shape.

[0018] Further, the steel mesh is similar to a spider web shape.

[0019] As can be seen from the above description, the steel mesh in the shape of a spider web has a high bearing capacity and meets the magnitude of the support force calculated based on the wedge body equilibrium theory.

[0020] Furthermore, the main reinforcement bars pass through the limiting members for limiting to realize the connection between the steel mesh and the primary support bolts.

[0021] Please refer to Figure 5 , furthermore, the limiting member is L-shaped, and one end of the limiting member is connected to one end of the primary support bolt.

[0022] As can be seen from the above description, the main reinforcement bars pass through the limiting members to realize the connection between the steel mesh and the primary support bolts. This connection method is easy to disassemble and is beneficial to the reuse of the support structure.

[0023] Furthermore, the main reinforcement bars passing through the limiting members are connected to the hub.

[0024] As can be seen from the above description, the hub drives the main reinforcement bars to tighten the steel mesh to achieve a pre-tightening effect. After the temporary support of the steel mesh is completely tightened, the hub is closed, and the hub is used to ensure the tightening effect of the steel mesh, conveniently realizing the active pressure effect of the steel mesh on the surrounding rock.

[0025] Furthermore, after the primary support bolts are embedded in the tunnel face, 5 - 8 cm are exposed.

[0026] As can be seen from the above description, 5 - 8 cm are exposed after the primary support bolts are embedded in the tunnel face for installing the limiting members.

[0027] Furthermore, a locking structure bolt chute is provided at one end of the primary support bolt close to the steel mesh.

[0028] Furthermore, the locking structure bolt chute includes a bolt and a nut. The nut is connected to the limiting member, and the bolt is threadedly connected to the nut.

[0029] As can be seen from the above description, the main reinforcement bars passing through the limiting members are wound between the nut and the bolt, and then the specific tightening of the nut and the bolt is adjusted by rotating the bolt to tighten the main reinforcement bars, reducing the effect of the tightening resistance of the hub.

[0030] Furthermore, it also includes the step of spraying concrete on the tunnel face before applying the steel mesh.

[0031] As can be seen from the above description, according to the fragmentation degree and the situation of caving and slag falling of the tunnel face after excavation, it is judged whether it is necessary to carry out the spraying of concrete on the tunnel face. For the tunnel face with broken surrounding rock, serious caving and slag falling, and poor integrity, spraying concrete is carried out for reinforcement; for the tunnel face with good integrity and high strength of the surrounding rock, it is not necessary to spray concrete on the tunnel face; for the surrounding rock that needs to be treated by spraying concrete on the tunnel face, the spraying of concrete on the tunnel face is carried out simultaneously with the initial spraying of concrete for the primary support.

[0032] Please refer to Figure 2, Further, it also includes the step of detecting whether the surrounding rock of the tunnel formation has strain hardening characteristics according to conventional triaxial experiments.

[0033] Further, mechanical excavation should be adopted during tunnel excavation.

[0034] As can be seen from the above description, the tunnel face after mechanical excavation has better flatness, which is convenient for the subsequent smooth construction of the active pressure temporary structure on the tunnel face. When the flatness of the tunnel face is difficult to meet the construction requirements of the temporary structure, artificial or mechanical measures should be taken to further process the flatness of the tunnel face.

[0035] Please refer to Figures 1 - 5 , Embodiment 1 of the present invention is: a method for actively supporting and strengthening a tunnel face, and the steps are as follows: S1: Conduct conventional triaxial experiments on the soil samples obtained by advanced drilling during the tunnel construction process. According to the conventional triaxial experiments, verify that the surrounding rock of this formation has strain hardening characteristics; For soil samples with strain hardening characteristics, their stress-strain curves and failure modes should meet the following two characteristics: ① As Figure 2 shown, in the stress-strain curve under conventional triaxial experiments, when the peak stress difference appears, as the strain increases, the stress difference basically no longer changes, the peak stress difference is not obvious, and the peak stress is basically the same as the stress difference after the peak; ② After the soil sample is damaged, a rupture surface appears, and the angle is approximately, and the rupture surface is quickly compacted during the loading process. After the experiment, the two conical damaged specimens are reconnected as a whole.

[0036] S2: Mechanically excavate the tunnel 1 in the surrounding rock with strain hardening characteristics to ensure that the tunnel face 2 has better flatness. When the flatness of the tunnel face 2 is difficult to meet the construction requirements of the temporary structure, take artificial or mechanical measures to further process the flatness of the tunnel face 2.

[0037] S3: According to the fragmentation degree and the situation of rock blocks falling off of the tunnel face 2 after excavation, judge whether it is necessary to apply shotcrete to the tunnel face 2, and apply shotcrete reinforcement to the tunnel face 2 with broken surrounding rock, serious rock block falling off, and poor integrity.

[0038] S3: Monitor the stability parameters of the surrounding rock in real time. Embed the primary support anchor rods 4 into the tunnel face 2 after excavation, with 5 - 8 cm of the primary support anchor rods 4 exposed. Weld the exposed end of the primary support anchor rod 4 to the bolt chute 7 of the locking structure and one end of the L-shaped limiting member 5. The bolt chute 7 of the locking structure includes a bolt and a nut, and the nut is connected to the limiting member 5; Lift the steel mesh 3 and erect it at the tunnel face 2. The steel mesh 3 includes main steel bars 8 and secondary steel bars. The main steel bars 8 are arranged radially, and the secondary steel bars are connected to the main steel bars 8 in a ring shape; Then, manually pass the main steel bars 8 through the limiting member 5 first, then through the bolt and nut for limitation, and then connect them to the hub 6; Then, pull the main steel bars 8 through the hub 6 to tighten the steel mesh 3 until it is completely taut and actively apply pressure to the tunnel face.

[0039] S4: After the stability parameters of the surrounding rock are maintained within the preset threshold parameter range and are in a self-stabilizing state, remove the steel mesh 3 and perform the next cycle of excavation operations; After the steel mesh 3 and the corresponding temporary support are removed, the tails of the anchor rods exposed to the air need to be processed to meet the requirements of the corresponding primary support design.

[0040] Please refer to Figures 3 - 5 For the second embodiment of the present invention: An active support structure for a tunnel face 2 includes primary support anchor rods 4, L-shaped limiting members 5, bolt chutes 7 of the locking structure, and a steel mesh 3; One end of the primary support anchor rod 4 is embedded in the tunnel face 2, and the other end is welded to the bolt chute 7 of the locking structure and one end of the L-shaped limiting member 5; The steel mesh 3 includes main steel bars 8 and secondary steel bars. The main steel bars 8 are arranged radially, and the secondary steel bars are connected to the main steel bars 8 in a ring shape; The bolt chute 7 of the locking structure includes a bolt and a nut. The nut is connected to the limiting member 5, the bolt is threadedly connected to the nut, the main steel bars 8 pass through the limiting member 5 first, then through the bolt and nut for limitation, and then are connected to the hub 6.

[0041] In summary, the active support and reinforcement method for the tunnel face provided by the present invention utilizes the self-healing characteristic of the fracture surface after the surrounding rock strain hardening. By means of the temporary support steel mesh structure and pulling the steel mesh to actively apply pressure to the tunnel face, it fully and effectively exerts the rock mass strain hardening characteristic, so that the fractured rock mass is re-compacted under the combined action of vertical load and active pressure, promotes the self-healing of the fractured rock mass, ensures the safety of tunnel construction, and the support process is simple in operation, saves materials, conforms to the concept of green construction, has popularization value in the construction of rock masses with strain hardening characteristics, and can effectively solve the problem of tunnel face stability under complex geological conditions such as softness and high rock mass fragmentation.

[0042] The above are only embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any equivalent transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in the relevant technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A method for actively supporting and strengthening a tunnel face, characterized in that It includes the following steps: Excavate a tunnel in the surrounding rock of a stratum with strain hardening characteristics; After the tunnel excavation, monitor the stability parameters of the surrounding rock in real time; Apply a steel mesh to the tunnel face, and connect the edge of the steel mesh to the edge of the tunnel face; Tighten the steel mesh through a hub until it is completely taut, so that the steel mesh actively applies pressure to the tunnel face; After the stability parameters of the surrounding rock are maintained within the preset threshold parameter range and reach the self-stabilized state, remove the steel mesh and carry out the excavation operation of the next cycle.

2. The active support and reinforcement method for tunnel face according to claim 1, wherein The steel mesh is fixed to the tunnel face by the primary support anchor rod. One end of the primary support anchor rod is embedded in the tunnel face, and the other end is connected to the steel mesh.

3. The active support and reinforcement method for tunnel face according to claim 2, wherein The other end of the primary support anchor rod is connected to a limiting member, and the steel mesh is detachably connected to the primary support anchor rod through the limiting member.

4. The active support and reinforcement method for tunnel face according to claim 3, characterized in that The steel mesh includes main steel bars and secondary steel bars. The main steel bars are arranged radially, and the secondary steel bars are connected to the main steel bars in a ring shape.

5. The active support and reinforcement method for tunnel face according to claim 4, wherein The main steel bar passes through the limiting member for limiting to realize the connection between the steel mesh and the primary support anchor rod.

6. The active support and reinforcement method for tunnel face according to claim 5, characterized in that The main steel bar passing through the limiting member is connected to the hub.

7. The active support and reinforcement method for tunnel face according to claim 3, characterized in that, The limiting member is L-shaped, and one end of the limiting member is connected to one end of the primary support anchor rod.

8. The active support and reinforcement method for tunnel face according to claim 2, characterized in that, After the primary support anchor rod is embedded in the tunnel face, 5 - 8 cm is exposed.

9. The active support and reinforcement method for tunnel face according to claim 1, wherein It also includes the step of spraying concrete on the tunnel face before applying the steel mesh.

10. The active support and reinforcement method for tunnel face according to claim 1, characterized in that, Mechanical excavation is used during tunnel excavation.

Images