A full-face yielding support system based on a steel pipe concrete support and a process thereof

Abstract

The application discloses a full-face yielding support system and process based on a steel pipe concrete support, which sequentially comprises internal pressure relief of surrounding rock, an anchor-spraying layer, a flexible filling layer, a wall-behind yielding layer and a steel pipe concrete support from surrounding rock to a roadway space. The internal pressure relief of surrounding rock is a pressure relief space formed by cutting of a hydraulic drill rod and a high-pressure water gun, and is internally periodically flushed by water flow. An anchoring section of the anchor-spraying layer is a conical bag type enlarged head. The flexible filling layer is formed by spraying of a plastic spraying material. The wall-behind yielding layer comprises a restrictive yielding layer and an open yielding layer. The restrictive yielding layer is a yielding block arranged at both sides of the roadway and a concrete layer with the same thickness as the yielding block. The open yielding layer is a reserved deformation space formed between the restrictive yielding layer and the steel pipe concrete support. The reserved deformation space is provided with a filler in the range thereof. The steel pipe concrete support is a retractable steel pipe concrete support.

Description

Technical Field

[0001] This invention belongs to the field of underground engineering support, specifically involving a full-section pressure relief support system and its construction technology. Background Technology

[0002] In recent years, with the increase in energy supply and mining intensity, deep tunnel support has encountered numerous problems such as large surrounding rock deformation, high ground pressure, and large tunnel floor heave, leading to increased risks of tunnel deformation and failure. Furthermore, deep surrounding rock tunnels are prone to deformation and failure due to the influence of "three highs and one disturbance." The bearing capacity and compressibility of the support structure are crucial to whether it can withstand the dynamic pressure of the surrounding rock in soft rock tunnels. Some support systems have been disclosed in existing technologies, such as a composite support structure, construction system, and method disclosed in patent publication number CN 111425216 A. However, due to the ductile failure of the rock strata caused by the in-situ stress during the anisotropic pressure process, the support structure and tunnel suffer severe deformation and damage, failing to provide sufficient support force to ensure tunnel stability. These support problems have become important tasks in deep mining and tunnel construction. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a full-section pressure-yielding support system and process based on steel-concrete composite supports, designed to solve the challenges of deep support, particularly in deep mining operations characterized by high ground stress, high ground temperature, and high karst water pressure. By employing pressure-yielding technology, the system can regulate the appropriate deformation of the surrounding rock during mining operations, thereby reducing surrounding rock stress, controlling deformation and damage, and adjusting the stress distribution. This system offers both significant load-bearing capacity and considerable flexibility, adapting to irregular displacements and deformations in the roadway while preventing structural layer damage and improving the stability and safety of the mining area.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0005] In a first aspect, the present invention provides a full-section pressure relief support system based on a steel-concrete composite support, comprising, sequentially from the surrounding rock to the tunnel space, an internal pressure relief layer, an anchor-sprayed layer, a flexible filling layer, a wall-back pressure relief layer, and a steel-concrete composite support; the internal pressure relief layer is cut into a pressure relief space of a certain size using a hydraulic drill rod and a high-pressure water gun; the anchoring section of the anchor-sprayed layer is a conical bag-type enlarged head, and the bag space is formed by a hole-reaming drill bit; the flexible filling layer is sprayed with a plastic spraying material; the wall-back pressure relief layer is divided into a restricted pressure relief layer and an open pressure relief layer; the restricted pressure relief layer includes pressure relief blocks set at the top, bottom, and sides of the tunnel and a concrete layer of the same thickness as the pressure relief blocks; a first steel mesh is set in the inner circle of the restricted pressure relief layer, and a second steel mesh is set in the outer circle of the steel-concrete composite support; the open pressure relief layer is a reserved deformation space formed between the first and second steel meshes; the reserved deformation space is filled with a filling material; the steel-concrete composite support is a collapsible steel-concrete composite support.

[0006] The various structural layers of this invention are organically combined to form a high-load-bearing, retractable, flexible, and full-section pressure-relief composite support system. In the joint operation of the support and the surrounding rock, it effectively controls and adjusts the redistribution of stress in the surrounding rock, preventing loosening and collapse, and enhancing the stability of the surrounding rock.

[0007] As a further technical solution, the pressure relief layer inside the surrounding rock is formed by drilling holes in the rock using a hydraulic drill rod, then cutting with a high-pressure water gun to gradually form the required space, then flushing out the rock fragments with water flow, and finally filling the drilling path with plastic material. After the space is formed, the pressure relief space is flushed periodically.

[0008] As a further technical solution, the anchoring section of the anchor spray layer is a conical enlarged head and a conical bladder. The space of the bladder is formed by a hole enlarging drill bit, and the conical bladder achieves self-locking after grouting and solidification.

[0009] As a further technical solution, the flexible filling layer is formed by spraying with a plastic spraying material.

[0010] As a further technical solution, the thickness of the flexible filling layer is determined according to the length of the anchor bolt end, covering the entire tunnel.

[0011] As a further technical solution, the restrictive pressure-relief layer includes pressure-relief blocks set at the top, bottom, and sides of the roadway, and a concrete layer of the same thickness as the pressure-relief blocks; the restrictive pressure-relief layer covers the entire roadway.

[0012] As a further technical solution, the reserved deformation space layer is filled with wooden backing boards at the top of the tunnel, and the remaining area is filled with gangue bags.

[0013] As a further technical solution, the steel pipe concrete support structure comprises multiple sections. The connection method at the ports between adjacent sections is as follows: connecting guide ribs are arranged inside one section of the support, and connecting pipes are arranged inside the other section of the support. The guide ribs are inserted into the connecting pipes, and then a joint sleeve is fitted around the outer ring of the connecting pipes and guide ribs, with the joint sleeve sealingly connected to the two sections of the support. The sealing connection flange is set at one end on the sleeve and the other end on the steel pipe. A large gasket is placed between the two flanges, and a ring of sealing material is sprayed to ensure that the hydraulic oil does not overflow. Solid hydraulic oil is injected into the internally threaded joint sleeve through a three-way valve using an injection gun. The three-way valve automatically opens when the hydraulic system is subjected to an external load exceeding its design bearing capacity to achieve rapid oil unloading. Once the bearing capacity of the hydraulic system returns to the normal level, the valve will automatically close.

[0014] Secondly, embodiments of the present invention also provide a construction process for a full-section pressure-yielding support system based on steel-concrete composite supports, as detailed below:

[0015] At the tunnel excavation face, anchor bolts are installed. The anchoring section of the anchor bolt is a conical bag-type enlarged head. The bag space is formed by a hole-enlarging drill bit. After the conical bag is grouted and solidified, it achieves self-locking. Reinforcing mesh is then laid.

[0016] A flexible filling layer is formed by spraying a plastic material onto the inner ring of the steel mesh;

[0017] Four pressure relief blocks are arranged at the top, bottom and sides of the tunnel, and concrete of the same thickness as the pressure relief blocks is sprayed as a restrictive pressure relief layer.

[0018] The first steel mesh is laid in the inner ring of the pressure layer;

[0019] Hydraulic drill rods and high-pressure water guns are used to cut a certain size of pressure relief space inside the surrounding rock, and the borehole is periodically hydraulically flushed.

[0020] Install a steel pipe concrete support frame, and set a second steel mesh around the outer ring of the steel pipe concrete support frame;

[0021] The deformation space reserved between the first and second steel mesh forms an open pressure-relief layer, and the space is filled with material.

[0022] As a further technical solution, the steel pipe concrete support structure comprises multiple sections. The connection method at the ports between adjacent sections is as follows: connecting guide ribs are arranged inside one section of the support, and connecting pipes are arranged inside the other section of the support. The guide ribs are inserted into the connecting pipes, and then a joint sleeve is fitted around the outer ring of the connecting pipes and guide ribs, with the joint sleeve sealingly connected to the two sections of the support. The sealing connection is a flange connection, with one end set on the sleeve and the other end set on the steel pipe. A large gasket is placed between the two flanges, and a ring of sealing material is sprayed to ensure that the hydraulic oil does not overflow. Solid hydraulic oil is injected into the internally threaded joint sleeve through a three-way valve using an injection gun. The three-way valve automatically opens when the hydraulic system is subjected to an external load exceeding its design bearing capacity to achieve rapid oil unloading. Once the bearing capacity of the hydraulic system returns to the normal level, the valve will automatically close.

[0023] As a further technical solution, the flexible filling layer is made of a plastic spray material, and its thickness is determined according to the length of the anchor bolt end, covering the entire tunnel.

[0024] As a further technical solution, the filling material is a wooden backing board filling the top of the tunnel, and gangue bags filling the remaining area to cover the entire tunnel.

[0025] As a further technical solution, a hydraulic drill rod of appropriate diameter and a high-pressure water gun are selected to form a pressure relief space inside the surrounding rock. Then, water flow is used to flush out rock fragments. Finally, the drilling path is filled with plastic material, and the pressure relief space is flushed regularly after the hole is formed.

[0026] The flexibility and retractability of the support structure of the present invention are achieved through the internal pressure relief layer of the surrounding rock, the anchor spray layer, the flexible filling layer, the pressure relief layer behind the wall, and the retractable steel pipe concrete support. Under the pressure of the surrounding rock, the elastic deformation properties accumulated inside the roadway's surrounding rock are first released through the deformation of the pressure relief borehole, thus releasing or transferring stress, eliminating or mitigating the risk of rockburst, and maintaining roadway stability. When the surrounding rock fragmentation between the anchor bolt tail and head causes the self-locking force of the enlarged head to exceed the limit, the anchor bolt tail tray system remains intact, and the enlarged head undergoes sliding displacement. At this point, the anchor bolt structure is stable, achieving overall anchor bolt pressure relief. When the surrounding rock stress causes the flexible filling layer to compress and deform, the thickness of the flexible filling layer decreases, but due to its plasticity, it will not lead to structural layer damage. The restrictive pressure relief layer uses compressed wooden blocks to achieve vertical and radial retractable pressure relief of the roadway. At the same time, it is sprayed with concrete structure, and the compressed wooden blocks and concrete are combined together. Through the spraying of concrete to limit excessive deformation and the retractable adjustment of the thickness of the compressed wooden blocks, effective compression of the structure is achieved, while ensuring the overall integrity and stability. The wooden backing of the open pressure relief layer is usually relatively dense and strong, which can effectively disperse the pressure from the roof. The combination of these two materials reduces the risk of excessive local stress on the structure. The plasticity of the gangue bags allows the structure to adjust its shape according to changes in external forces. This combination enables the structure to maintain balance under external pressure and adapt to pressure changes, thus improving the structure's reliability and adaptability. When the surrounding rock pressure is transmitted to the collapsible steel-concrete composite support through the layered structure, the hydraulic system of the support and the large gaskets at the joints allow the steel pipe to collapse, absorbing and mitigating the force from the surrounding rock. When the external load exceeds its design capacity, the valves of the hydraulic system automatically open to quickly unload oil. Once the hydraulic system's load capacity returns to normal, the valves automatically close. The large gaskets have a certain degree of elasticity, allowing the two flanges to expand and contract in the bolt direction while maintaining contact with the steel pipe surface during expansion and contraction, ensuring a seal. After deformation within the design range, the high-strength load-bearing capacity of the steel-concrete composite support then comes into play to resist continued external pressure.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. This invention introduces a deformation mechanism of pressure relief boreholes to release the elastic deformation energy accumulated in the surrounding rock of the roadway, thereby releasing or transferring stress, reducing or eliminating the danger of rockburst, and maintaining the stability of the roadway.

[0029] 2. This invention achieves self-locking by grouting and solidifying the conical bag of the anchor bolt anchoring section. The self-locking force is less than the ultimate bearing capacity of the anchor bolt tray. When the self-locking force of the enlarged head exceeds the limit due to the swelling of the surrounding rock between the anchor bolt tail and the anchor bolt head, the anchor bolt tail tray system is not damaged, and the enlarged head undergoes sliding displacement. At this time, the anchor bolt structure is stable, and the overall pressure relief of the anchor bolt is achieved.

[0030] 3. By using steel mesh and flexible filling layer as active support, the deformation and delamination of the surrounding rock are effectively prevented and the pressure is flexibly released under closed conditions. By setting up multiple layers of steel mesh, the surrounding rock between the anchor bolts is maintained, effectively preventing the falling of small loose rocks. At the same time, this design not only improves the adhesion of high-strength concrete, but also makes the stress in the sprayed layer uniformly distributed, strengthening the seismic, shear and tensile resistance of the sprayed layer.

[0031] 4. The restrictive compressive layer composed of compressed wood blocks and concrete provides the tunnel with flexible compressibility in both the vertical and radial directions. The compressibility of the wood blocks and the deformation-limiting coating of the concrete work together to provide sufficient flexibility for the structure and ensure its integrity and stability to adapt to different external pressures and environmental changes.

[0032] 5. An open pressure-relief layer consisting of wooden backing boards and gangue bags. The wooden backing boards filling the top can disperse the pressure of the top plate and provide a uniform weight distribution. The gangue bags on the sides and bottom plate are not only economical as filling materials, but also have great plasticity. The combination of the two materials makes the structure more adaptable and better able to cope with various pressure changes, which helps to improve the stability of the structure.

[0033] 6. Steel-concrete composite supports, as passive supports, provide high load-bearing capacity. However, their rigidity is excessive. Therefore, a large gasket is installed between the hydraulic system and the flange at the connecting sleeve, allowing the steel pipe to retract and absorb and mitigate the force from the surrounding rock. When the external load on the hydraulic system exceeds its design capacity, the valve automatically opens to quickly unload oil. Once the hydraulic system's load-bearing capacity returns to normal, the valve automatically closes. The large gasket has a certain degree of elasticity, allowing the two flanges to expand and contract in the bolt direction, while maintaining contact between the gasket and the steel pipe surface during expansion and contraction to ensure a seal. Flexible connections are installed between the steel-concrete composite supports to form retractable steel-concrete composite supports, successfully achieving significant contraction of the support structure. After deformation to the design range, the high-strength load-bearing capacity of the steel-concrete composite supports then comes into play to resist continued external pressure. This combination of passive and rigid support achieves the effect of "constant resistance and pressure relief in the early stage, and increased resistance and retraction in the later stage," conforming to the theory of combined support. Attached Figure Description

[0034] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0035] Figure 1 This is a plan view of the composite support system proposed in this invention;

[0036] Figure 2This is a schematic diagram of the hydraulic system proposed in this invention;

[0037] Figure 3 This is a schematic diagram of the anchor bolt enlarged head before and after sliding displacement proposed in this invention;

[0038] Figure 4 This is an overall effect diagram after the implementation of the present invention;

[0039] In the diagram: 1—Anchor bolt; 2—Flexible filling layer; 3—Concrete; 4—Compressed wood block; 5—Gange bag; 6—Wooden backing board; 7—Steel pipe concrete support; 8—Joint sleeve; 9—Burnt steel mesh; 10—Surrounding rock pressure relief space; 11—Flange; 12—Large gasket; 13—Three-way valve; 14—Guide steel bar; 15—Connecting pipe; 16—Solid hydraulic oil; 17—Enlarged head sliding space; 18—Conical bladder; 19—Butterfly tray; 20—Tunnel floor. Detailed Implementation

[0040] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is intended to include the plural form as well. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0042] For ease of description, the words "up," "down," "left," and "right" appearing in this invention only indicate that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves, and do not limit the structure. They are merely for the purpose of facilitating the description of this invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] The full-face support system is a full-face pressure-yielding support system based on steel-concrete composite supports. It adopts the principle of pressure-yielding support, that is, during the sequential installation of the supports, the supports bear the ground pressure and protect the integrity of the roadway.

[0044] To address the shortcomings of existing technologies, this embodiment provides a full-section pressure-yielding support system and construction method using steel-concrete composite supports, aiming to solve the challenges of deep support, especially in deep mining operations characterized by high ground stress, high ground temperature, and high karst water pressure. By employing pressure-yielding technology, the system can reduce surrounding rock stress, control deformation and damage, and adjust stress distribution during mining operations through appropriate deformation of the surrounding rock. This results in a system with both high load-bearing capacity and significant flexibility, capable of adapting to irregular displacement and deformation in the tunnel while preventing structural layer damage, thus improving the stability and safety of the mining area. Furthermore, it possesses the ability to buffer and absorb energy generated by rockbursts. The invention comprises, sequentially from the surrounding rock to the tunnel space, an internal pressure-relief layer, a shotcrete layer, a flexible filling layer, a backfill pressure-yielding layer, and a steel-concrete composite support. These structures are combined to form a high-load-bearing, flexible, and full-section pressure-yielding composite support system. In the joint operation of support and surrounding rock, the redistribution of stress in the surrounding rock is effectively controlled and adjusted to avoid loosening and collapse of the surrounding rock and to enhance its stability.

[0045] Specifically, the full-section pressure-relief support system of the steel-concrete composite support consists of, from the outermost layer to the innermost layer, a pressure-relief layer inside the surrounding rock, an anchor-sprayed layer, a flexible filling layer, a pressure-relief layer behind the wall, and the steel-concrete composite support layer. The pressure-relief space inside the surrounding rock effectively alleviates the horizontal compression of the roadway caused by the horizontal pressure of the surrounding rock. The anchor-sprayed layer and the flexible filling layer, as active supports, effectively prevent deformation and delamination of the surrounding rock and provide flexible pressure relief under closed conditions. The restricted pressure-relief layer, composed of pressure-relief blocks and concrete, not only ensures the integrity and stability of the structure but also provides sufficient flexibility. The open pressure-relief layer, composed of wooden backing boards and gangue bags, makes the structure more adaptable and better able to cope with various pressure changes. The steel-concrete composite support, as a passive support, provides high load-bearing capacity, but its rigidity is too high. Therefore, flexible connections are set inside the steel-concrete composite casing to form a retractable steel-concrete composite support. This successfully achieves a significant reduction in the support structure, combining active and passive elements, and balancing rigidity and flexibility, achieving the effect of "constant resistance and pressure relief in the early stage, and increased resistance and retraction in the later stage," which conforms to the theory of combined support.

[0046] In specific implementation, anchor bolts 1 are driven into the tunnel excavation section, and steel mesh is laid to form temporary support. Three high-strength anchor cables are arranged at the top to form the above-mentioned anchor spray layer. A flexible material is sprayed using special spraying equipment to form a flexible filling layer 2. Then, compressed wooden blocks 4 (pressure relief blocks) are arranged at the top, bottom and side walls of the tunnel. A layer of concrete 3 is sprayed according to the thickness of the compressed wooden blocks 4 to form a restrictive pressure relief layer. A hydraulic drill rod of appropriate diameter is selected to drill holes in the rock. Then, a high-pressure water gun is used to cut and gradually form the required space. Then, water flow is used to flush out the rock debris. Finally, the drilling path is filled with plastic material. Finally, a steel pipe concrete support 7 is installed. A reserved deformation space (composed of wooden backing board 6 and gangue 5) is formed between the steel pipe concrete support 7 and the pressure relief layer behind the wall. Finally, a flexible pressure relief and high-strength load-bearing composite support system is formed.

[0047] The cross-sectional shape of the tunnel is determined based on the magnitude and direction of the ground pressure acting on the tunnel and the properties of the surrounding rock it passes through. When subjected to high impact and low pressure, the pressure is transmitted in sequence, and the pressure is relieved, released and absorbed through the internal pressure relief layer, anchor spray layer, flexible filling layer and pressure relief layer behind the wall structure. The steel pipe concrete support provides high-strength passive support, forming a high-strength and retractable composite support system that first yields and then resists, and provides stable support.

[0048] The aforementioned compressed wooden block 4 (pressure relief block): The grain direction is crucial to the mechanical properties of the compressed wooden block. Placing the wood grain direction parallel to the pressure direction allows for a larger compression amount. When the structure is subjected to horizontal surrounding rock pressure, the top and bottom pressure relief blocks are compressed; when the structure is subjected to vertical surrounding rock pressure, the pressure relief blocks on both sides are compressed, simultaneously achieving vertical and radial compressibility of the roadway.

[0049] Furthermore, the thickness of the compressed wooden block 4 is generally between 0.5-1m. After undergoing tunnel deformation, the compression amount should be around 50%. If the compressed wooden block 4 is too hard, it will reduce the structure's pressure-bearing capacity; if it is too soft, it will lead to excessive compression and premature compression, failing to provide pressure-bearing when the tunnel is subjected to disturbance loads.

[0050] Furthermore, the compressed wood block 4 is made of high-density fiberboard, which is a board made from wood fiber or other plant fibers through fiber preparation, application of synthetic resin, and pressing under heat and pressure. High-density fiberboard has a uniform structure, fine texture, stable performance, impact resistance, and is easy to process.

[0051] Furthermore, in this embodiment, the anchoring section 1 of the anchor spray layer is a conical bag-type enlarged head. The bag space is formed by the enlarged drill bit. After the conical bag is grouted and solidified, it achieves self-locking. The self-locking force is less than the ultimate bearing capacity of the anchor rod tray (butterfly tray 19). When the self-locking force of the enlarged head exceeds the limit due to the swelling of the surrounding rock between the anchor rod tail and the anchor rod head, the anchor rod tail tray system is not damaged, and the enlarged head undergoes sliding displacement. At this time, the anchor rod structure is stable, and the anchor rod as a whole is relieved of pressure.

[0052] Furthermore, the flexible filling layer 2 in this embodiment uses a plastic spraying material, which has high construction efficiency, standardized quality, and the thickness is determined according to the length of the anchor bolt end. It covers the entire roadway and can relieve pressure and slow down when the roadway pressure is too high, and then transfer it to the pressure relief layer, which is then supported by the support.

[0053] Furthermore, in this example, four compressed wooden blocks 4 and concrete 3 of the same thickness as the compressed wooden blocks are arranged at the top, bottom and two sides as a restricted pressure relief layer; a certain size of deformation space is reserved between the steel mesh and the steel pipe concrete. In the reserved deformation space, the top plate is filled with wooden backing board 6, and the side and bottom plate areas are filled with gangue 5 as an open pressure relief layer.

[0054] Furthermore, in this example, the internal pressure relief space 10 of the surrounding rock is located on both sides of the roadway. A hydraulic drill rod of appropriate diameter is selected to drill the rock according to the engineering needs. Then, a high-pressure water gun is used to cut and gradually form the required space. Then, water flow is used to flush out the rock fragments. Finally, the drilling path is filled with plastic material, and the pressure relief space is periodically flushed with water in the later stage.

[0055] Furthermore, in this embodiment, the steel pipe concrete support 7 is manufactured using a factory steel pipe machine, with slots at the ends. After grouting is completed on the ground, it is transported to the well and installed using a hoisting machine. The connection method at the joints of each support section is to install connecting guide bars inside one end of the support and connecting pipes inside the other end to ensure precise connection between the steel pipe supports. A hydraulic system is arranged inside the sleeve at the connection point, and flange connections and sealing materials are used to ensure that the hydraulic oil does not leak out. The deformable space after compression of the connecting steel bars is 0.1m. The horizontal shrinkage of the entire support is 0.1m×cos30°×2=0.173m, and the vertical shrinkage is 0.1m×sin30°×2=0.1m.

[0056] Furthermore, in this embodiment, the restrictive design allows for the laying of burr-reinforced steel mesh 9 on both the inner side of the pressure layer and the outer side of the steel-concrete composite. The steel mesh is fabricated and welded in the factory, adhering closely to the rock surface to increase the concrete adhesion area.

[0057] Furthermore, the total resizable dimensions of the structure in this example are: horizontal direction: 0.174m × wood block thickness × 50% + flexible filler layer thickness, vertical direction: 0.1m × wood block thickness × 50% + flexible filler layer thickness;

[0058] Furthermore, the overall structure of this embodiment is as follows: Figure 1 , Figure 4As shown, at the tunnel face, anchor bolts (anchor bolt specifications not less than φ22×2400mm) are installed. The anchor bolt anchoring section 1 is a conical bag-type enlarged head. The bag space is formed by a reaming drill bit. After the conical bag is grouted and solidified, it achieves self-locking. Ordinary steel mesh is laid. A flexible filling layer 2 is formed by spraying a plastic material using special equipment. Four compressed wooden blocks 4 are placed at the top, bottom, and two sides of the tunnel. Concrete 3 of the same thickness as the compressed wooden blocks is sprayed as a relief layer. A burred steel mesh 9 is laid on the inner side. A certain size of deformation space is reserved between the restrictive relief layer and the steel pipe concrete support. The top of the reserved deformation space is filled with wooden backing boards 6, and the side walls and bottom plate are filled with... 5. Fill the gangue bags; drill a certain size of surrounding rock pressure relief space 10 at both sides of the tunnel using a hydraulic drill bit. After completion, high-pressure water flow regularly flushes the rock debris in the space; the steel pipe concrete support structure 7 is generally composed of 4 sections. The installation method at the contact point of the two support ends is as follows: a connecting guide steel bar 14 is arranged inside one section of the support, a connecting pipe 15 is arranged inside the other end, and a hydraulic system is arranged inside the sleeve 8 connected at both ends. Flanges 11 are set at the support interface and the end of the sleeve, and a large gasket is set between the two flanges. The surface of the large gasket 12 has bolt holes equal in number to those of the flanges 11 and aligned one by one. Then, a ring of sealing material is sprayed to ensure that the solid hydraulic oil 16 does not overflow.

[0059] The flexibility and compressibility of the support structure are achieved through the internal pressure relief layer, anchor spraying layer, flexible filling layer, pressure relief layer behind the wall, and flexible steel pipe concrete. Under the pressure of the surrounding rock, the elastic deformation properties accumulated inside the roadway's surrounding rock are first released through the deformation of the pressure relief borehole, thus releasing or transferring stress, eliminating or mitigating the risk of rockburst, and maintaining roadway stability. When the surrounding rock fragmentation between the anchor bolt tail and head causes the self-locking force of the enlarged head to exceed the limit, the anchor bolt tail tray system remains intact, and the enlarged head undergoes sliding displacement. At this point, the anchor bolt structure is stable, achieving overall anchor bolt pressure relief. When the surrounding rock stress causes the flexible filling layer to compress and deform, the thickness of the flexible filling layer decreases, but due to its plasticity, it will not lead to structural layer damage. The restrictive pressure relief layer uses compressed wooden blocks to achieve vertical and radial retractable pressure relief of the roadway, while also being sprayed with concrete. This layer design combines the compressed wooden blocks and concrete, and through the spraying of concrete to limit excessive deformation and the retractable adjustment of the thickness of the compressed wooden blocks, effective compression of the structure is achieved, ensuring overall integrity and stability. The wooden backing of the open pressure relief layer is usually dense and strong, effectively dispersing the roof. The pressure is reduced, minimizing the risk of excessive local stress on the structure. Simultaneously, the plasticity of the gangue bags allows the structure to adjust its shape according to changes in external forces. This combination of materials enables the layered structure to maintain balance under external pressure and adapt to pressure variations, thereby improving the structure's reliability and adaptability. When the surrounding rock pressure is transmitted to the collapsible steel-concrete composite support through the layered structure, the hydraulic system of the support and the large gasket between the flanges allow the entire steel pipe to collapse, absorbing and mitigating the force from the surrounding rock. When the external load exceeds the design capacity of the hydraulic system, the valves automatically open to quickly unload oil. Once the hydraulic system's load capacity returns to normal, the valves automatically close. The large gaskets have a certain degree of elasticity, allowing the two flanges to expand and contract in the bolt direction, while maintaining contact between the large gaskets and the steel pipe surface during expansion and contraction to ensure a seal. After deformation within the design range, the high-strength load-bearing capacity of the steel-concrete composite support then provides resistance to continued external pressure.

[0060] As a supplement to other underground engineering support structures, temporary support—anchor-mesh-shotcrete—needs to be erected before installing permanent support facilities. The initial anchor-mesh-shotcrete coating allows the anchor bolts, concrete spray layer, and surrounding rock to form a cohesive system, preventing rock mass loosening and separation. It transforms a certain thickness of surrounding rock into a self-supporting arch, penetrating rock fissures, sealing joints, reinforcing structural surfaces and bedding planes, effectively stabilizing the surrounding rock, improving its integrity and self-supporting capacity, and inhibiting deformation. Anchor cables, fixed to prestressed steel strands at both ends of the stabilized roadway rock mass, directly generate anti-slip resistance on the contact surface, increasing anti-slip friction resistance and keeping the structural surface under compression. This improves the integrity of the mine rock mass, fundamentally improves its mechanical properties, effectively controls rock mass displacement, and promotes its stability.

[0061] To ensure the strength of the steel pipes, the curved steel pipes are prefabricated on the ground. The radius of curvature of the arc is designed according to the cross-sectional dimensions of the tunnel. Connecting guide bars and splicing pipes are pre-installed on the steel pipe concrete arc slab. The steel pipe concrete support structure is divided into 4 to 6 sections, generally 4 sections—the top arc section, the two side sections, and the inverted bottom arch section—and the sections are connected by sleeves. The connection method is as follows:

[0062] like Figure 2 As shown, a connecting pipe 15 is installed on one section of the support, and a guide steel bar 14 is installed on the other section. The guide steel bar 14 is inserted into the connecting pipe 15, and then a connector sleeve 8 is fitted around the outer ring of the connecting pipe 15 and the guide steel bar 14. Solid hydraulic oil is injected into the internally threaded connector sleeve 8 through a three-way valve 13 using an injection gun. The connection is made with flanges, and a large gasket 12 is placed between the two flanges 11 to ensure that there is no leakage at the connection point. After the solid hydraulic oil fills the connector sleeve 8 and the connecting pipe 15, it forces the steel pipe to rise. When the steel pipe is raised close to the roof, the injection gun is pulled out to provide initial support force to the working face. As the pressure on the roadway roof continues to increase, when the load of the hydraulic system exceeds the rated working resistance, the safety valve of the three-way valve 13 automatically opens, hydraulic oil overflows, the pressure in the connector sleeve 8 decreases accordingly, and the support retracts; the retraction of a section of the connecting steel bar is about 0.1m. When the load of the steel pipe concrete support is lower than the working resistance, the safety valve closes, allowing the support to regain balance.

[0063] The construction process of the system proposed in this embodiment is as follows:

[0064] The first step, preliminary preparation: First, conduct rigorous testing of the walls and roof to ensure solidity. Immediately afterward, perform initial shotcreting for temporary support and leveling of the roof and walls. Then, install anchor bolts and mesh. Finally, perform a second shotcreting to form the final shape. The anchor bolts use conical enlarged heads, perpendicular to the tunnel outline and rock surface. The pocket space is created using a borehole drill bit. After the conical pocket grout solidifies, it achieves self-locking. The length of the exposed anchor plate should be less than 5 cm, and it should be sufficient to allow the nut to be level. Tighten the nut with a special torque wrench, with a preload greater than 100 N·m.

[0065] The second step involves laying a layer of burred steel mesh inside the flexible infill layer, followed by spraying high-strength concrete. During spraying, the nozzle should be perpendicular to the surface being sprayed, and the distance between the nozzle and the surface should not exceed 1.5 meters. The nozzle should move slowly in a spiral motion, following a circular or elliptical trajectory. Strict control of the water-cement ratio, air pressure, and the amount of accelerator is crucial to minimize rebound. The spraying and mesh installation should follow a top-down sequence, starting with the top and then the sides.

[0066] The third step is to place four compressed wooden blocks 4 on the top, bottom and side walls of the tunnel, and spray a layer of concrete 3 according to the thickness of the compressed wooden blocks 4 to form a restrictive compression layer.

[0067] The fourth step is to reserve an open space of a certain size between the restricted pressure layer and the steel pipe concrete support, fill the top with wooden backing board 6, and fill the side walls and bottom plate with gangue bags 5 as an open pressure layer.

[0068] The fifth step involves drilling holes in the rock on both sides of the tunnel using hydraulic drill rods of appropriate diameters according to the project requirements. Then, high-pressure water guns are used to cut and gradually form the required surrounding rock pressure relief space 10. High-pressure water jets are then used to flush out the rock fragments. After completion, the pipes are filled with gangue bags 5, and the pressure relief space is flushed regularly in the later stages.

[0069] Step 6: After the ground grouting of the steel pipe support is completed, the steel pipe support is assembled using an installation machine and an internal buckle sleeve. Before injecting 16 solid hydraulic oil at the connection of the two arc plates, the flange and large gasket are firmly connected with bolts. After the injection is completed, a ring of sealing material is sprayed to ensure that the hydraulic oil does not leak out. The back plate material is filled. Before installation, 2 to 3 I-beams must be placed in the reverse bottom arch section. The first support and every 10 supports thereafter are anchored.

[0070] Repeat the above steps to complete the construction of all support layers, achieving the effect of "constant resistance and pressure relief in the early stage, and increased resistance and shrinkage in the later stage".

[0071] Furthermore, steel-concrete composite supports come in various forms, including circular supports, straight-wall semi-circular arch supports, elliptical supports, and shallow-bottomed arch circular supports. The cross-sectional shape of the steel-concrete composite support is determined by the surrounding rock properties and the tunnel cross-section. Shallow-bottomed arch circular supports are used to withstand greater top and side pressures. The proportion of shotcrete materials must be determined, and the water-cement ratio, air pressure, and amount of accelerator must be strictly controlled to minimize rebound.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A full-section pressure-yielding support system based on steel-concrete composite supports, characterized in that: The tunnel space, from the surrounding rock to the tunnel floor, sequentially includes an internal pressure relief layer, a shotcrete layer, a flexible filling layer, a backfill pressure relief layer, and a steel-concrete composite support. The anchoring section of the shotcrete layer is a conical, bag-shaped enlarged head, with the bag space formed by a reaming drill bit. The flexible filling layer is sprayed with a plastic spraying material. The backfill pressure relief layer consists of a restricted pressure relief layer and an open pressure relief layer. The restricted pressure relief layer includes pressure relief blocks located at the top, bottom, and sides of the tunnel, as well as a concrete layer of the same thickness as the pressure relief blocks. A first reinforcing mesh is installed in the inner ring of the restricted pressure relief layer, and a second reinforcing mesh is installed in the outer ring of the steel-concrete composite support. The open pressure relief layer is a reserved deformation space formed between the first and second reinforcing meshes. The reserved deformation space is filled within the area of ​​the tunnel roof, side walls, and floor. The steel-concrete composite support is a collapsible steel-concrete composite support. The steel-concrete composite support structure comprises multiple sections. The connection method at the ports between adjacent sections is as follows: connecting guide ribs are arranged inside one section of the support, and connecting pipes are arranged inside the other section. The guide ribs are inserted into the connecting pipes, and then a joint sleeve is fitted around the outer ring of the connecting pipes and guide ribs, with the joint sleeve sealing the connection between the two support sections. The sealing connection is a flange connection, with a large gasket between the two flanges, and a ring of sealing material is sprayed to ensure that the hydraulic oil does not overflow. Solid hydraulic oil is injected into the internally threaded joint sleeve through a three-way valve using an injection gun. The three-way valve automatically opens when the hydraulic system is subjected to an external load exceeding its design bearing capacity to achieve rapid oil unloading. Once the bearing capacity of the hydraulic system returns to normal, the valve will automatically close.

2. The full-section pressure-yielding support system based on steel-concrete composite supports as described in claim 1, characterized in that: The pressure relief layer inside the surrounding rock is the pressure relief space created by periodic hydraulic cutting after the initial drilling and hydraulic cutting to ensure pressure relief.

3. The full-section pressure-yielding support system based on steel-concrete composite supports as described in claim 1, characterized in that: The conical bladder achieves self-locking after grouting solidifies, and the self-locking force is less than the ultimate bearing capacity of the anchor plate.

4. The full-section pressure-yielding support system based on steel-concrete composite supports as described in claim 1, characterized in that: The thickness of the flexible filling layer is determined according to the length of the anchor bolt end, and it covers the entire tunnel.

5. The full-section pressure-yielding support system based on steel-concrete composite supports as described in claim 1, characterized in that: The aforementioned anchor spray layer, flexible filling layer, and backfill pressure layer cover the entire tunnel.

6. A construction process for a full-section pressure-yielding support system based on steel-concrete composite supports, characterized in that: The full-section pressure relief support system based on steel-concrete composite supports as described in any one of claims 1-5 is implemented as follows: At the tunnel excavation face, anchor bolts are installed. The anchoring section of the anchor bolt is a conical bag-type enlarged head. The bag space is formed by a hole-enlarging drill bit. After the conical bag is grouted and solidified, it achieves self-locking. Reinforcing mesh is then laid. A flexible filling layer is formed by spraying a plastic material onto the inner ring of the steel mesh; Four pressure relief blocks are arranged at the top, bottom and sides of the tunnel, and concrete of the same thickness as the pressure relief blocks is sprayed as a restrictive pressure relief layer. The first steel mesh is laid in the inner ring of the pressure layer; Hydraulic drill rods and high-pressure water guns are used to cut a certain size of pressure relief space inside the surrounding rock, and the borehole is periodically hydraulically flushed. Install a steel pipe concrete support frame, and set a second steel mesh around the outer ring of the steel pipe concrete support frame; The deformation space reserved between the first and second steel mesh forms an open pressure-relief layer, and the space is filled with material.

7. The construction process of a full-section pressure-yielding support system based on steel-concrete composite supports as described in claim 6, characterized in that: The steel-concrete composite support structure comprises multiple sections. The connection method at the ports between adjacent sections is as follows: connecting guide ribs are arranged inside one section of the support, and connecting pipes are arranged inside the other section. The guide ribs are inserted into the connecting pipes, and then a joint sleeve is fitted around the outer ring of the connecting pipes and guide ribs, with the joint sleeve sealing the connection between the two support sections. The sealing connection is a flange connection, with a large gasket between the two flanges, and a ring of sealing material is sprayed to ensure that the hydraulic oil does not overflow. Solid hydraulic oil is injected into the internally threaded joint sleeve through a three-way valve using an injection gun. The three-way valve automatically opens when the hydraulic system is subjected to an external load exceeding its design bearing capacity to achieve rapid oil unloading. Once the bearing capacity of the hydraulic system returns to normal, the valve will automatically close.

8. The construction process of a full-section pressure-yielding support system based on steel-concrete composite supports as described in claim 6, characterized in that: The flexible filling layer is made of a plastic spray material, and its thickness is determined according to the length of the anchor bolt end, covering the entire tunnel. The top of the filler is a wooden backing board, and the rest of the space is filled with gangue bags.

9. The construction process of a full-section pressure-yielding support system based on steel-concrete composite supports as described in claim 7, characterized in that: Select a hydraulic drill rod of appropriate diameter and a high-pressure water gun to create a pressure relief space inside the surrounding rock. Then, use water flow to flush out rock fragments. Finally, fill the drilling path with plastic material and flush the pressure relief space regularly after drilling.

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