Tunnel weak surrounding rock face core soil pre-reinforcement ring excavation support structure

Abstract

The utility model provides a tunnel soft weak surrounding rock face core soil pre-reinforcement annular excavation support structure relates to tunnel excavation support structure technology, specifically discloses arch portion advance support structure and face support structure, and the arch portion advance support structure is installed in the tunnel top, and the face support structure is installed in the tunnel face core soil, and the inner wall of tunnel is provided with annular excavation groove, and the annular support structure is installed in the annular excavation groove, and the reinforcing structure is equipped between any two adjacent annular support structures, and the fibre anchor rod is implanted to form the reinforced composite, and effectively resists the shearing slip of face core soil, and the oblique advance support optimizes the load transmission path, and effectively decomposes the top pressure into axial compression stress and surrounding rock tangential constraint force, and the annular support structure is installed in the annular excavation groove, forms the closed radial bone, and provides powerful annular support.

Description

Technical Field

[0001] This utility model relates to the technical field of tunnel excavation support structure, specifically to a ring-shaped excavation support structure for the core soil of the tunnel face in the case of weak surrounding rock. Background Technology

[0002] The research on soft rock tunnel excavation methods by major railway and highway design institutes in China generally includes the bench method (including two-bench, three-bench, micro-bench, long bench, short bench, ultra-short bench, etc.), the arc-shaped pilot tunnel method (also known as the upper arc pilot core soil retention method or the ring pilot tunnel method), the CD method (middle diaphragm wall method), the CRD method (cross middle diaphragm wall method), the double side wall pilot tunnel method, and the middle pilot tunnel method.

[0003] In existing technologies, tunnel support is generally carried out in multiple steps from top to bottom and from left to right. The time for forming the support ring is relatively long, and the distance from the tunnel face is often more than 20m. During the construction process, the support structure relies solely on the support of anchor bolts to control settlement and deformation, resulting in an unstable foundation. This is extremely unfavorable for deformation control in soft rock tunnels, often causing deformation to continue to develop and eventually leading to large deformations. This results in support encroachment, cracking of shotcrete, twisting and damage of steel frames, ultimately necessitating support removal, widening of the excavation, and reconstruction, which significantly increases construction costs and severely delays the construction period.

[0004] When constructing tunnels in soft rock sections with large deformation, conventional construction methods involve multi-stage, top-down, sectional excavation, with support constructed step by step in the order of arch, sidewall, and bottom. This inevitably leads to a longer time for the support to form a closed ring and an increased distance between the support and the tunnel face. If the support is not closed, the stress conditions will be poor, the deformation control effect will be poor, and it will be difficult to control the deformation of the surrounding rock near the tunnel face.

[0005] When constructing tunnels in soft rock sections with large deformation, the tunnel face is prone to extrusion-induced large deformation of the surrounding rock, making it difficult to ensure that the tunnel face remains stable and to solve the problems of construction step distance and rapid ring formation of support. Utility Model Content

[0006] The purpose of this utility model is to provide a pre-reinforced ring-shaped excavation support structure for the core soil of the tunnel face in soft surrounding rock, which can solve the problems mentioned in the background art and address the shortcomings of the existing technology.

[0007] The technical solution of this utility model is implemented as follows:

[0008] The utility model provides a pre-reinforced annular excavation support structure for the core soil of a tunnel face in soft surrounding rock, including an arch pre-support structure and a face support structure. The arch pre-support structure is installed at the top of the tunnel, and the face support structure is installed in the core soil of the tunnel face. Annular excavation grooves are opened on the inner wall of the tunnel, and annular support structures are installed in each annular excavation groove. A reinforcement structure is provided between any two adjacent annular support structures.

[0009] In some technical solutions of this utility model, the arch advance support structure is inclinedly set at the top of the tunnel.

[0010] In some technical solutions of this utility model, the tunnel face support structure consists of several fiber anchors, and an array of several fiber anchors is installed in the core soil of the tunnel face.

[0011] In some technical solutions of this utility model, a first concrete layer is sprayed inside the annular excavation trench.

[0012] Some technical solutions of this utility model also include several system anchor bolts, which are set in the annular excavation trench along the circumference of the tunnel.

[0013] In some technical solutions of this utility model, the reinforcing structure includes several connecting structures, which are arranged between any two adjacent annular support structures along the extension direction of the annular support structure.

[0014] In some technical solutions of this utility model, a steel mesh is provided between any two adjacent annular support structures, and a second concrete layer is provided between any two adjacent annular support structures to cover the steel mesh.

[0015] In some technical solutions of this utility model, the arch support structure is an advanced small guide pipe, an advanced anchor bolt, or an advanced pipe roof.

[0016] In some technical solutions of this utility model, concrete pads for positioning the annular support structure are installed inside the annular excavation trench. The concrete pads abut against the outer wall of the annular support structure. Positioning anchors connected to the annular support structure are installed inside the annular excavation trench.

[0017] Compared to existing technologies, this invention has at least the following advantages or beneficial effects: A reinforced composite structure is formed by embedding high-strength fiber anchors in a mesh pattern, effectively resisting shear slippage of the core soil at the working face. The fiber anchors possess high tensile strength, providing strong pull-out resistance; simultaneously, their low shear strength facilitates cutting by excavation machinery, without hindering subsequent construction. The inclined pre-support optimizes the load transfer path, effectively decomposing the top pressure into axial compressive stress and surrounding rock tangential constraint force. The annular support structure, promptly installed within the annular excavation trench, forms a closed radial skeleton, providing strong circumferential support. The synergistic effect of multi-level support (annular support, first concrete layer, system anchors, second concrete layer, steel mesh, etc.) significantly reduces the risk of collapse. Adjacent annular support structures, through reinforced structural welding, transform discrete units into a continuous force-bearing system, greatly improving the overall system stiffness, effectively suppressing surrounding rock convergence and circumferential deformation; the steel mesh and shotcrete layer provide uniform radial support, reducing the risk of surface spalling and improving impact resistance. Attached Figure Description

[0018] Figure 1 This is a front structural diagram of the present invention.

[0019] Figure 2 This is a side view of the present invention.

[0020] Figure 3 This is a schematic diagram of the installation structure of the ring support structure in this utility model.

[0021] Figure 4 This is a schematic diagram of the installation structure of the annular support structure and the positioning anchor rod in this utility model.

[0022] Reference numerals in the attached drawings: 1. Arch pre-support structure; 2. First concrete layer; 3. System anchor bolt; 4. Circular excavation trench; 5. Arch wall lining; 6. Second concrete layer; 7. Fiber anchor bolt; 8. Invert arch; 9. Circular support structure; 10. Connecting structure; 11. Steel mesh; 12. Positioning anchor bolt; 13. Spacer block. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0025] Example

[0026] This utility model provides a ring-shaped excavation support structure for pre-reinforced core soil at the tunnel face in soft surrounding rock, such as... Figures 1-4 As shown, the system includes an arch pre-support structure 1 and a tunnel face support structure. The arch pre-support structure 1 is installed at the top of the tunnel to ensure the stability of the surrounding rock at the arch during tunnel excavation. The tunnel face support structure is installed within the core soil at the tunnel face to ensure the stability of the core soil during tunnel excavation. An annular excavation trench 4 is formed on the inner wall of the tunnel. Annular support structures 9 are installed at equal intervals within the annular excavation trench 4. A reinforcement structure is provided between any two adjacent annular support structures 9. The annular support structures 9 are installed as soon as possible after the annular excavation trench 4 is excavated, forming a closed radial skeleton and creating spatial collaborative support. The annular support system reduces the convergence of the surrounding rock, subsequently forming multi-level support to reduce the overall risk of collapse.

[0027] In some technical solutions of this utility model, the arch pre-support structure 1 is inclinedly installed at the top of the tunnel. The inclination angle optimizes the load transfer path, decomposing the top pressure into compressive stress along the support axis and tangential constraint force of the surrounding rock, so as to ensure the stability of the arch surrounding rock during tunnel excavation.

[0028] In some technical solutions of this utility model, the arch pre-support structure 1 is a pre-supported small guide pipe, a pre-supported anchor bolt, or a pre-supported pipe roof. The type can be selected according to the surrounding rock conditions.

[0029] Preferably, the arch support can be achieved using advanced central pipe roofing with a pipe diameter of 76mm, a length of 9-12m, and a longitudinal overlap of not less than 3m; or advanced small guide pipes with a diameter of 42mm, a length of 4.5m, and a longitudinal overlap of not less than 1m. Parameters can also be adjusted based on actual geological conditions.

[0030] In some technical solutions of this utility model, the tunnel face support structure consists of a plurality of fiber anchors 7, which are arrayed and installed within the core soil of the tunnel face. A plurality of fiber anchors 7 are implanted in a grid pattern within the core soil region of the tunnel face, penetrating deep into the surrounding rock and soil to form a reinforced composite that resists shear slippage. Because fiber anchors 7 have higher tensile strength than ordinary anchors, using fiber anchors 7 to reinforce the tunnel face provides higher pull-out resistance for the stability of the tunnel face. Simultaneously, due to their low shear strength, they can be easily cut by excavating machinery, without adversely affecting mechanical excavation.

[0031] Preferably, the fiber anchor bolts 7 at the working face can be made of glass fiber or resin fiber, with a solid bolt diameter of 25mm or a hollow bolt diameter of 32mm, a length of 9-12m, and a longitudinal overlap of not less than 3m. The fiber anchor bolts 7 are arranged in a 1.2-1.5m x 1.2-1.5m staggered pattern.

[0032] After completing the arch pre-support and the face pre-reinforcement, the surrounding rock mechanical conditions were greatly improved, providing better construction conditions for the excavation of the annular trench 4.

[0033] In some technical solutions of this utility model, a first concrete layer 2 is sprayed inside the annular excavation trench 4. The first concrete layer 2 is formed after quick-setting concrete is sprayed inside the annular excavation trench 4. The concrete layer fills the uneven surfaces of the surrounding rock, increases the contact area of ​​the support, disperses local stress, and avoids stress concentration that could lead to rock crushing.

[0034] Tunnel-specific milling machines and excavators should be prioritized, especially milling machines with built-in muck removal devices, which are more effective. After completing the above pre-reinforcement, full-section excavation will be carried out, with the excavation time expected to be within 2 hours. Immediately after excavation, initial shotcrete will be applied to seal the surrounding rock surface to reduce stress concentration and prevent surface cracks from developing into deeper layers.

[0035] In some technical solutions of this utility model, a plurality of system anchor bolts 3 are also included, which are arranged circumferentially within the annular excavation trench 4. The system anchor bolts 3 are inserted at intervals along the circumference of the tunnel within the annular excavation trench 4. The system anchor bolts 3 penetrate deep into the stable rock strata to form end anchorage, working in conjunction with the annular support to constrain the surrounding rock delamination. This controls the relaxation range of the surrounding rock and reduces cracking of the first concrete layer 2. The initial sprayed first concrete layer 2 seals the surrounding rock surface, reducing stress concentration and the propagation of surface cracks to deeper layers. The system anchor bolts 3 are installed promptly after the initial sprayed first concrete layer 2 is completed to control plastic deformation of the surrounding rock.

[0036] The ring support structure 9 is installed by using an arch frame installation machine to install the pre-made steel frame (ring support structure 9) from bottom to top. Concrete pads 13 and positioning anchors 12 can be used for positioning. The longitudinal connection between the ring support structure and the previous frame and the installation of the steel mesh 11 are completed, and then the second concrete is sprayed.

[0037] The length of the system anchor bolt 3 is set according to the level of large deformation. It is recommended to use 4.5m for minor large deformation, 6-9m for moderate large deformation, and 9-12m for severe large deformation. In areas with severe large deformation, anchor cables can be used instead of anchor bolts if necessary. Anchor bolts can be hollow grouting anchor bolts, self-drilling anchor bolts, etc.

[0038] The thickness of the invert arch 8 and the arch wall lining 5 shall be no less than 60cm for two-lane tunnels and no less than 70cm for three-lane tunnels. The distance between the arch wall lining 5 and the tunnel face can be adjusted according to the monitoring and measurement results, but should not exceed 50m.

[0039] The spacing between any two adjacent ring support structures 9 is generally 0.5m-1.5m.

[0040] In some technical solutions of this utility model, the reinforcing structure includes several connecting structures 10, which are arranged between any two adjacent annular support structures 9 along the extension direction of the annular support structure 9. H-beam steel connectors are welded between adjacent annular support structures 9 to form longitudinal reinforcing ribs. This transforms the discrete support unit into a continuous force-bearing system, thereby improving the overall stiffness of the support system and suppressing circumferential joint deformation.

[0041] In some technical solutions of this utility model, a steel mesh 11 is provided between any two adjacent annular support structures 9, and a second concrete layer 6 is provided between any two adjacent annular support structures 9 to cover the steel mesh 11. The steel mesh 11 is laid between adjacent annular supports, and the second concrete layer 6 is sprayed to form a thick covering layer. The steel mesh 11 bears the concrete shrinkage stress, and the second concrete layer 6 provides radial support resistance. This reduces the risk of surface rock spalling and improves the impact resistance of the support structure.

[0042] In some technical solutions of this utility model, a concrete pad 13 for positioning the annular support structure 9 is installed inside the annular excavation trench 4. The concrete pad 13 abuts against the outer wall of the annular support structure 9. A positioning anchor rod 12 connected to the annular support structure 9 is installed inside the annular excavation trench 4. This improves the installation accuracy of the annular support structure 9.

[0043] The first concrete layer 2 is recommended to use C30 early-strength concrete, which can provide high early strength and effectively control the deformation development of the surrounding rock. The thickness of the first concrete layer 2 should not be less than 4cm, and the thickness of the second concrete layer 6 should be at least 2cm to completely cover the ring support structure.

[0044] To prevent mechanical equipment from damaging the initial support structure during subsequent excavation, the slag can be evenly spread on the tunnel floor to form a working platform. As the excavation at the tunnel face progresses, the paving will also gradually advance. When the invert 8 and filling construction are carried out, the slag at the tunnel floor can be cleaned up. Vehicles can pass through the invert 8 trestle bridge when traveling from the section where the invert 8 and filling have been completed to the tunnel face, without affecting the construction of the invert 8 and filling. For the support sections that have been completed, the deformation of the surrounding rock and support should be closely observed through monitoring and measurement. When the deformation converges, the construction of the waterproof membrane and secondary lining can be carried out.

[0045] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A tunnel weak surrounding rock face core soil pre-reinforced ring excavation support structure, characterized in that, It includes an arch pre-support structure (1) and a tunnel face support structure. The arch pre-support structure (1) is installed at the top of the tunnel, and the tunnel face support structure is installed in the core soil of the tunnel face. An annular excavation groove (4) is opened on the inner wall of the tunnel. Annular support structures (9) are installed at equal intervals in the annular excavation groove (4). A reinforcement structure is provided between any two adjacent annular support structures (9).

2. The pre-reinforced ring-shaped excavation support structure for the core soil of the tunnel face in weak surrounding rock according to claim 1, characterized in that, The arch support structure (1) is inclinedly set at the top of the tunnel.

3. The pre-reinforced ring-shaped excavation support structure for the core soil of the tunnel face in weak surrounding rock according to claim 1, characterized in that, The tunnel face support structure consists of several fiber anchors (7), which are arrayed and installed in the core soil of the tunnel face.

4. The pre-reinforced ring-shaped excavation support structure for the core soil of the tunnel face in weak surrounding rock according to claim 3, characterized in that, The annular excavation trench (4) is sprayed with a first concrete layer (2).

5. The pre-reinforced ring-shaped excavation support structure for the core soil of the tunnel face in weak surrounding rock according to claim 4, characterized in that, It also includes several system anchors (3), which are set in the annular excavation trench (4) along the circumference of the tunnel.

6. The pre-reinforced ring-shaped excavation support structure for the core soil of the tunnel face in weak surrounding rock according to claim 4 or 5, characterized in that, The reinforcement structure includes several connecting structures (10), which are arranged between any two adjacent annular support structures (9) along the extension direction of the annular support structure (9).

7. The pre-reinforced ring-shaped excavation support structure for the core soil of the tunnel face in weak surrounding rock according to claim 6, characterized in that, A steel mesh (11) is provided between any two adjacent annular support structures (9), and a second concrete layer (6) is provided between any two adjacent annular support structures (9) to cover the steel mesh (11).

8. The pre-reinforced ring-shaped excavation support structure for the core soil of the tunnel face in weak surrounding rock according to claim 2, characterized in that, The arch support structure (1) is an advanced small guide pipe, an advanced anchor bolt, or an advanced pipe shed.

9. The pre-reinforced ring-shaped excavation support structure for the core soil of the tunnel face in weak surrounding rock according to claim 1, characterized in that, A concrete pad (13) for positioning the annular support structure (9) is installed in the annular excavation trench (4). The concrete pad (13) abuts against the outer wall of the annular support structure (9). A positioning anchor (12) connected to the annular support structure (9) is installed in the annular excavation trench (4).

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