A method of supporting a chamber

Abstract

The application discloses a supporting method for a cavern, and relates to the technical field of underground construction, which comprises the following steps: arranging a surface supporting layer on the surface of the surrounding rock of the cavern; arranging a net-shaped connecting steel bar layer on the surface supporting layer; and arranging a concrete beam structure on at least part of the surface of the connecting steel bar layer. Under the joint action of the surface supporting layer, the net-shaped connecting steel bar layer and the concrete beam structure, the overall supporting capacity of the anchoring system is improved, a greater range of supporting force can be provided, and the phenomenon of local collapse of the surrounding rock caused by the overloading failure of the local anchoring system and the overlarge deformation of the surrounding rock can be avoided.

Description

Technical Field

[0001] This application relates to the field of underground construction technology, and in particular to a method for supporting caverns. Background Technology

[0002] In related technologies, existing support methods mainly rely on shotcrete anchoring. The combined strength of horizontally reinforced anchor bolt systems is insufficient to provide adequate resistance to the surrounding rock in large underground caverns, preventing large local deformations. This can lead to cracking of the shotcrete, rockfall, or localized rockfalls, posing a significant threat to the safety of construction workers and the normal operation of construction equipment. Furthermore, subsequent reinforcement requires clearing the cracked shotcrete and collapsed rock / rock fragments from the damaged areas, backfilling the remaining surrounding rock with concrete, and reinforcing with prestressed anchor cables / piles, which significantly increases the construction period and investment. Summary of the Invention

[0003] The embodiments of this application are intended to at least solve one of the problems existing in the prior art or related technologies.

[0004] In view of this, this application provides a method for supporting a cavern, comprising:

[0005] A surface support layer is installed on the surrounding rock surface of the cavern;

[0006] A mesh-like connecting steel reinforcement layer is installed in the surface support layer;

[0007] A concrete beam structure is provided on at least a portion of the surface of the mesh-connected steel reinforcement layer.

[0008] In one feasible implementation, the step of setting a mesh-like connecting steel reinforcement layer in the surface support layer includes:

[0009] Multiple anchor bolts are installed in the surrounding rock of the cavern so that the anchor bolts pass through the surface support layer, and the exposed ends of adjacent anchor bolts are welded together with connecting steel bars to form the mesh-like connecting steel bar layer.

[0010] In one feasible implementation, setting a surface support layer on the surrounding rock surface of the cavern includes: fixing a steel mesh on the surrounding rock surface of the cavern and spraying concrete onto the fixed steel mesh to form the surface support layer.

[0011] In one feasible implementation, the thickness of the sprayed concrete is 100 mm.

[0012] In one feasible implementation, the provision of a concrete beam structure on at least a portion of the surface of the connecting steel reinforcement layer includes:

[0013] Multiple prestressed anchor cables are installed in the surrounding rock of the cavern so that the prestressed anchor cables pass through the surface support layer and the mesh connecting steel reinforcement layer;

[0014] Concrete anchor piers are formed by casting concrete at the exposed ends of prestressed anchor cables, and adjacent concrete anchor piers are cast and connected to form a lattice-type concrete beam.

[0015] In one feasible implementation, multiple anchor rods are anchored at one end after passing through the damaged and fractured area of ​​the surrounding rock, while the other end is exposed on the surface of the surrounding rock, and the connecting steel bars in the mesh-connecting steel bar layer are arranged in an alternating manner.

[0016] In one feasible implementation, the prestressed anchor cable is anchored beyond the boundary of the damaged and fractured zone of the surrounding rock, entering the stable zone of the surrounding rock for anchoring.

[0017] In one feasible implementation, the lattice-type concrete beam is rectangularly arranged on the surface of the surface support layer, and the prestressed anchor cables and anchor rods are arranged alternately.

[0018] In one feasible implementation, the spacing of the prestressed anchor cables is 2m to 3m, and the length of the prestressed anchor cables is 15m to 40m.

[0019] In one feasible implementation, the diameter of the anchor bolt is 20mm to 32mm, and the spacing between the anchor bolts is 0.8m to 1.2m.

[0020] Compared to existing technologies, this application offers at least the following advantages: The embodiments provided in this application connect the exposed ends of multiple adjacent anchor rods by setting up a mesh-like connecting steel reinforcement layer. Simultaneously, a lattice-type concrete beam connects adjacent prestressed anchor cable anchor blocks and multiple anchor rods, connecting steel reinforcement layers, and surface support layers intersecting with the lattice-type concrete beam, fixing them to the surrounding rock. This improves the overall support strength in two ways: Firstly, the prestressed anchor cables provide deep reaction force, pressing the surface support layer, connecting steel reinforcement layer, and concrete beam structure onto the surrounding rock surface and applying a larger support force to the surrounding rock, compensating for the lateral confining pressure loss caused by excavation unloading. Secondly, the strength of the surrounding rock is improved by combining anchor rods, anchor cables, and surrounding rock into a composite material. This effectively avoids local anchorage overload failure caused by large deformation of the surrounding rock and the resulting local collapse of the surrounding rock. Attached Figure Description

[0021] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0022] Figure 1 A schematic flowchart illustrating a cavern support method according to an embodiment of this application;

[0023] Figure 2A schematic structural diagram from one angle illustrating an application scenario of a cavern support method according to an embodiment of this application;

[0024] Figure 3 This application provides a schematic structural diagram of another application scenario of a cavern support method according to one embodiment;

[0025] Figure 4 This application provides a schematic cross-sectional structural diagram of an application scenario for a cavern support method according to an embodiment;

[0026] The markings in the diagram are: anchor bolt 100, mesh connecting steel reinforcement layer 200, prestressed anchor cable 300, concrete anchor block 400, concrete beam structure 500, surface support layer 600, steeply inclined structural surface 700, and side wall 800. Detailed Implementation

[0027] To better understand the above technical solutions, the technical solutions of the embodiments of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0028] like Figure 1 As shown, the cavern support method of one embodiment provided in this application may include steps S110 to S130.

[0029] In step S110, a surface support layer 600 is installed on the surface of the surrounding rock of the cavern;

[0030] For example, the aforementioned cavern can be an underground space and passage excavated in the rock mass of an engineering project, or it can be a cavern (group), tunnel (cavity), or roadway. This embodiment selects a cavern containing directional, densely dipping structural planes in the surrounding rock. The aforementioned surrounding rock surface can be the surrounding rock of an ore body or the surrounding rock of a rock mass. In this embodiment, the selected rock mass contains directional, densely dipping structural planes within the stress redistribution influence range after cavern excavation. The aforementioned surface support layer 600 can be a concrete layer or a shotcrete layer; in this embodiment, shotcrete is selected. The aforementioned surface support layer 600 can be set on the entire surface of the surrounding rock, using shotcrete attached to a reinforcing mesh to form the surface support layer 600. This prevents initial deformation and localized rock spalling.

[0031] In step S120, a mesh-connecting steel reinforcement layer 200 is provided in the surface support layer 600;

[0032] For example, the above-mentioned mesh-connecting steel reinforcement layer 200 can be formed by connecting steel bars. After the surface support layer 600 is formed, the mesh-connecting steel reinforcement layer 200 is set. The steel bars are connected and fixed according to the position of the anchor rod 100 to form the mesh-connecting steel reinforcement layer 200, so that multiple anchor rods 100 are combined with the surface support layer 600 to improve the overall support capacity.

[0033] In step S130, a concrete beam structure 500 is provided on at least a portion of the surface of the connecting steel reinforcement layer 200.

[0034] For example, at least part of the above can be made of concrete beams or all of them can be made of concrete beams. The concrete beam structure combines multiple prestressed anchor cables 300, mesh connecting steel reinforcement layer 200 and surface support layer 600 into a whole, which applies a larger range of support force to the surrounding rock and avoids the local overload failure of the anchoring system caused by the deformation of the surrounding rock and the induction of local collapse of the surrounding rock.

[0035] According to some embodiments, the step of providing a mesh-connecting steel reinforcement layer 200 in the surface support layer 600 may include:

[0036] Multiple anchor bolts 100 are installed in the surrounding rock of the aforementioned cavern so that the anchor bolts 100 pass through the surface support layer 600;

[0037] The aforementioned mesh-like connecting steel bar layer 200 is formed by welding the exposed ends of adjacent anchor rods 100 with connecting steel bars.

[0038] For example, the anchor bolt 100 mentioned above can be a slotted pipe anchor bolt or a wedge-type metal anchor bolt, etc., and is not limited in this embodiment. Before setting the mesh connection layer 200, the anchor bolt 100 needs to be fixed. Anchor bolt holes are drilled on the surrounding rock surface at the anchor bolt installation location, arranged at a large angle to the structural surface as much as possible. The anchor bolt 100 is constructed according to the layered excavation requirements, and over-excavation is strictly prohibited. The anchor bolt 100 needs to penetrate the surface support layer 600 and the damaged and fractured area of ​​the surrounding rock to form a reinforced zone where the surrounding rock and the anchor bolt share the load. Connecting the exposed ends of the anchor bolt 100 with connecting steel bars to form a mesh connection steel bar layer allows the individual anchor bolts to be connected into a whole, improving the support capacity.

[0039] According to some embodiments, the step of setting a surface support layer 600 on the surrounding rock surface of the cavern may include:

[0040] A steel mesh was fixed to the surface of the surrounding rock of the aforementioned cavern;

[0041] Concrete is sprayed onto the fixed steel mesh to form the surface support layer 600.

[0042] For example, the above-mentioned shotcrete construction with reinforced mesh needs to be coordinated with the tunnel excavation, and carried out in a continuous operation mode to avoid interference between the two. Reinforcing mesh is fixed to the surface of the surrounding rock using pre-inserted reinforcing bars, and then shotcrete is sprayed onto the mesh to form a shotcrete layer, which is used to withstand the initial deformation of the surrounding rock and prevent localized rockfall.

[0043] According to some embodiments, the sprayed thickness of the concrete is 20mm to 150mm.

[0044] For example, the thickness of the sprayed concrete, ranging from 20mm to 150mm, should be determined based on the geological conditions of the surrounding rock; it should meet the toughness requirements of the geological conditions, deformation magnitude, and engineering type of the surrounding rock. In this embodiment, a sprayed concrete thickness of 100mm is selected. A 100mm sprayed concrete thickness achieves the required support capacity while making construction more convenient.

[0045] According to some embodiments, the step of constructing a concrete beam structure 500 on at least a portion of the surface of the aforementioned mesh-connected steel reinforcement layer 200 may include:

[0046] Multiple prestressed anchor cables 300 are installed in the surrounding rock of the cavern so that the prestressed anchor cables 300 pass through the surface support layer 600 and the mesh connecting steel reinforcement layer 200;

[0047] Concrete anchor piers 400 are formed by casting at the exposed end of the prestressed anchor cable 300, and adjacent concrete anchor piers 400 are cast and connected to form a lattice concrete beam.

[0048] For example, the prestressed anchor cable 300 mentioned above can be either a bonded prestressed anchor cable or a hollow prestressed anchor cable. This embodiment selects a hollow prestressed anchor cable. It should be noted that the above concrete beam structure is a lattice-type concrete beam, which is easier to control and provides more uniform stress. The anchor holes are accurately positioned on the surrounding rock surface during drilling. When installing the anchor cables, each steel strand should be straight, without twisting or crossing, and evenly arranged. The anchoring is performed to meet all the technical requirements of the support structure design specifications. The exposed ends of the anchor cables are then poured to form concrete anchor blocks 400. Adjacent concrete anchor blocks 400 are then connected to form a lattice-type concrete beam. The shape of the lattice structure is easier to control, and construction is more convenient.

[0049] In some embodiments, when anchoring prestressed anchor cables 300, the hole position should be accurate. During drilling, construction records should be kept for each borehole, including geological changes, drilling status, drilling pressure, drilling speed, and groundwater conditions. After the anchor holes are drilled, the hole diameter and depth should be checked, and the anchor hole coordinates, inclination angle, and azimuth should be rechecked. After all checks are passed, the anchor cables can be installed. Before installation, the anchor hole number should be verified. After confirmation, the hole should be blown with high-pressure air, and the anchor cable body should be manually and slowly placed into the hole. The length of the exposed steel strand outside the hole should be measured, and the length of the anchor cable inside the hole should be calculated to ensure the anchoring length. Then, anchoring grouting should be performed to fill the anchoring section and tensioning section of the anchor cable without leaving any gaps. After the concrete in the hole reaches the design strength, the anchor cable is tensioned to the design load tonnage to provide stress for the prestressed anchor cables 300. Following this, a lattice-type concrete beam 500 is poured, connecting the surface support layer 600, the mesh-connecting steel reinforcement layer 200, the anchor bolts 100, and the prestressed anchor cables 300 to form a unified whole. The force exerted by the prestressed anchor cables 300 presses the entire support structure against the surrounding rock surface, resulting in a wider range of support force application and stronger support capacity. Compared to existing point-support methods, the support method proposed in this application combines surface-to-surface approaches, allowing for the application of support forces over a larger area and a higher safety factor.

[0050] According to some embodiments, the above-described S120 may include:

[0051] The aforementioned multiple anchor rods 100 are anchored after passing through the damaged and fractured area of ​​the surrounding rock at one end, and the other end is exposed on the surface of the surrounding rock. The connecting steel bars in the mesh connecting steel bar layer 200 are arranged in an alternating manner.

[0052] For example, it should be noted that the aforementioned damaged and fractured zone of the surrounding rock refers to an unstable area where the mechanical properties of the surrounding rock have irreversibly deteriorated due to the excavation of the cavern. When anchor bolt 100 is anchored, the anchor bolt passes through the damaged and fractured zone of the surrounding rock and is anchored thereafter, forming a reinforced zone where the surrounding rock and the anchor bolt share the load.

[0053] According to some embodiments, the step of extending the anchoring depth of the prestressed anchor cable 300 beyond the boundary of the damaged fracture zone of the surrounding rock may include:

[0054] For example, it should be noted that the aforementioned boundary of the damaged and fractured zone beyond the surrounding rock refers to the anchoring section of the prestressed anchor cable being fixed in a stable area deep within the surrounding rock. During the anchoring of the prestressed anchor cable 300, precise hole positioning is ensured during drilling. Construction records are kept for each hole's geological changes, drilling status, drilling pressure, drilling speed, groundwater levels, etc. After drilling is completed, the hole diameter and depth are checked, and the hole position, inclination, and azimuth are also rechecked. After all checks are passed, the anchor cable is installed. Before installation, the anchor hole number is verified. After confirmation, the hole is blown open with high-pressure air, and the anchor cable body is manually and slowly placed into the hole. The length of the exposed steel strand outside the hole is measured, and the length of the anchor cable inside the hole is calculated to ensure the anchoring length. The anchoring end is fixed to stable rock. Then, anchoring grouting is performed to fill both the anchoring and tensioning sections of the anchor cable, leaving no gaps. After the concrete inside the hole reaches the design strength, tensioning is performed to provide stress to the prestressed anchor cable 300. The tensioning and locking process is determined through on-site tensioning tests. Next, a lattice-type concrete beam 500 is poured, integrating the surface support layer 600, the mesh connecting steel reinforcement layer 200, the anchor bolts 100, and the prestressed anchor cables 300 into a single unit. The deep reaction force provided by the prestressed anchor cables 300 presses the entire support structure firmly against the surrounding rock surface, enhancing its support capacity. Compared to previous support methods that primarily relied on point support, this method combines surface-to-surface approaches, applying support force over a wider area and resulting in a higher safety factor.

[0055] According to some embodiments, the above-described S120 may include:

[0056] The lattice-type concrete beams are rectangularly arranged on the surface of the aforementioned surface support layer, and the aforementioned prestressed anchor cables 300 and anchor rods 100 are arranged alternately.

[0057] For example, the above-mentioned lattice concrete beam is rectangularly arranged on the surface of the above-mentioned surface support layer 600. The rectangular shape is easier to control and makes construction more convenient. The prestressed anchor cables 300 and anchor rods 100 are staggered on the surface of the surrounding rock, and the stress is relatively more uniform, which can improve the overall support capacity.

[0058] According to some embodiments, the spacing of the prestressed anchor cables is 2m to 3m, and the length of the prestressed anchor cables is 15m to 40m.

[0059] For example, the prestressed anchor cable 300 needs to be able to use deep reaction force to press the entire support structure onto the surface of the surrounding rock. Therefore, in this embodiment of the application, the prestressed anchor cable spacing is selected as 2m and the length of the prestressed anchor cable is 20m.

[0060] According to some embodiments, the diameter of the anchor bolt 100 is 20mm to 32mm, and the spacing between the anchor bolts 100 is 0.8m to 1.2m.

[0061] For example, when the anchor rod 100 is anchored, the anchor rod 100 body is used to bear the shear stress brought by the surrounding rock. Therefore, the anchor rod 100 itself must bear this part of the stress. At the same time, the anchor rod 100 also plays a role in fixing the surface support layer 600 and the mesh connecting steel reinforcement layer 200. Therefore, in this embodiment, the anchor rod diameter is selected as 20mm and the anchor rod spacing is 1m, which can better bear the shear stress and improve the support force.

[0062] For example, an integrated support system for deep and shallow layers of surrounding rock in a large cavern with directional, dense, steeply dipping structural surfaces includes the following steps:

[0063] A steel mesh is fixed to the surface of the surrounding rock using pre-inserted reinforcing bars, and then shotcrete is sprayed onto the steel mesh to form a shotcrete layer. The thickness of the shotcrete layer is 100mm. When using shotcrete for initial support, the thickness of the layer should be determined according to the geological conditions of the surrounding rock; it should meet the toughness requirements of the geological conditions, deformation magnitude, and project type of the surrounding rock.

[0064] Before commencing construction of anchor bolt 100, the installation of water and electricity lines and the erection of temporary facilities must be carried out according to the actual site conditions. Drainage ditches should be laid around the construction site. Anchor bolt 100 construction should be carried out according to the requirements of layered excavation, and over-excavation is strictly prohibited. After the tunnel excavation, anchor bolt 100 construction and other processes such as shotcrete should be started immediately. Anchor bolt 100 needs to penetrate the surface support layer for fixing. When fixing anchor bolt 100, first use a drill bit that matches the diameter of the anchor bolt 100 to drill anchor bolt holes on the wall at the anchor bolt installation position, and arrange them at a large angle with the structural surface as much as possible. Push the anchor bolt into the anchor bolt hole. After the anchoring agent cures, the anchor bolt is anchored in the anchor bolt hole. After the connection is fixed, the exposed end of the anchor bolt is welded to the adjacent steel mesh to ensure anchoring stress. Individual anchor bolts are prone to damage at the anchoring end under shear stress. Connect the exposed ends of anchor bolt 100 with connecting steel bars to form a mesh-like connecting steel bar layer.

[0065] Prestressed anchor cables 300 are installed for anchoring. During drilling, ensure precise hole positioning. Before installation, verify the anchor hole number. After confirmation, blow the hole with high-pressure air and manually and slowly insert the anchor cable body into the hole. Measure the length of the exposed steel strand outside the hole and calculate the length of the anchor cable inside the hole to ensure the anchoring section is firmly fixed in the rock. Then, perform anchoring grouting, filling both the anchoring and tensioning sections of the anchor cable completely, leaving no gaps. After the concrete in the hole reaches the design strength, tensioning is performed to provide prestress to the prestressed anchor cables 300. Afterwards, pour the lattice-type concrete beam 500, connecting the surface support layer 600, the mesh connecting steel reinforcement layer 200, the anchor rods 100, and the prestressed anchor cables 300 to form a whole. Through the force of the prestressed anchor cables 300, the entire support structure is pressed against the surrounding rock surface, resulting in stronger support capacity and the ability to apply support force over a wider area. On the other hand, the anchoring effect can improve the strength of the surrounding rock and avoid the local overload failure of the anchoring system caused by large deformation of the surrounding rock with directional dense steep dipping structural planes and the resulting local collapse of the surrounding rock.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present 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 method for supporting a cavern, characterized in that, include: Setting a surface support layer on the surrounding rock surface of the cavern includes: fixing a steel mesh to the surrounding rock surface of the cavern; and spraying concrete onto the fixed steel mesh to form the surface support layer. Setting a mesh-like connecting steel reinforcement layer in the surface support layer includes: setting multiple anchor rods in the surrounding rock of the cavern so that the anchor rods pass through the surface support layer; and forming the mesh-like connecting steel reinforcement layer by welding the exposed ends of adjacent anchor rods with connecting steel bars. A concrete beam structure is provided on at least a portion of the surface of the mesh-connecting steel reinforcement layer, including: providing multiple prestressed anchor cables in the surrounding rock of the cavern so that the prestressed anchor cables pass through the surface support layer and the mesh-connecting steel reinforcement layer; casting concrete anchor piers at the exposed ends of the prestressed anchor cables to form concrete anchor piers, and casting adjacent concrete anchor piers to connect them to form a lattice-type concrete beam. The lattice-type concrete beams are rectangularly arranged on the surface of the surface support layer, and the prestressed anchor cables and anchor rods are arranged alternately. One end of each of the multiple anchor rods passes through the damaged and fractured area of ​​the surrounding rock and is anchored thereafter, while the other end protrudes from the surface of the surrounding rock. The connecting steel bars in the mesh-like connecting steel bar layer are arranged in an alternating pattern. The prestressed anchor cable is anchored beyond the boundary of the damaged and fractured zone of the surrounding rock and enters the stable zone of the surrounding rock for anchoring. The diameter of the anchor rod is 20mm~32mm, and the spacing between the anchor rods is 0.8m~1.2m.

2. The method according to claim 1, characterized in that, The thickness of the sprayed concrete is 20mm to 150mm.

3. The method according to claim 1, characterized in that, The spacing between the prestressed anchor cables is 2m to 3m, and the length of the prestressed anchor cables is 15m to 40m.

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