Construction device and method for reducing rebound rate of tunnel sprayed concrete

Abstract

The invention discloses a construction device and method for reducing the springback rate of tunnel sprayed concrete. The construction device comprises a tunnel preliminary bracing mechanism, a springback reducing mechanism and concrete spraying equipment. The construction method comprises the following steps: 1, constructing a tunnel primary support mechanism and a rebound reducing mechanism; secondly, concrete is prepared, and spraying operation is started through concrete spraying equipment; 3, carrying out real-time net catching on the sprayed concrete rebound material; fourthly, the spraying thickness of sprayed concrete is gradually increased; and fifthly, the first step, the second step, the third step and the fourth step are cycled for many times, and after the tunnel preliminary bracing mechanism and the rebound lowering mechanism are integrally or sectionally installed in the length direction of the tunnel, jetting operation is completed till construction is finished. According to the rebound reducing mechanism, an elastic catching net can be formed on the surface of concrete, the rebound rate of tunnel sprayed concrete is remarkably reduced, meanwhile, the elastic net generates rebound shrinkage stress on concrete micro-cracks, closing and repairing of the micro-cracks are achieved, the crack resistance of the concrete is improved, and the quality of the concrete is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of shotcrete construction, and particularly relates to a construction device and method for reducing the rebound rate of shotcrete in a tunnel. BACKGROUND

[0002] Shotcrete has the advantages of fast construction speed, high early strength, and no need for vibration, and is widely used in tunnel (road) support, slope support, water conservancy projects, rail transit, and the like. In the field of tunnel construction, the initial support of Class III and Class IV and above surrounding rock structures generally adopts a combined support form combining anchor rods, steel arches, steel mesh, and shotcrete.

[0003] As the core material of the initial support of a project, the rebound rate of shotcrete is a key indicator affecting the construction quality and cost. The rebound rate of shotcrete refers to the mass ratio of rebounded material not adhered to the sprayed surface to the total shotcrete. In traditional tunnel construction, the rebound rate of shotcrete (such as C20 and C25) generally exceeds 25%. Especially under poor conditions such as poor stability of surrounding rock (Class IV and above) or large deformation of soft rock, the rebound rate can even reach 50%. Investigations show that the main components of the rebounded material are coarse aggregate (generally 5-10 mm), which is most likely to rebound due to its large mass and high kinetic energy when impacting the sprayed surface, followed by a small amount of fine aggregate (sand) and cement slurry. A high rebound rate of shotcrete leads to obvious waste of materials, reduced construction efficiency, increased cost of slag removal, and affects the construction effect. SUMMARY

[0004] The present application aims to solve the technical problems in the prior art, and provides a construction device and method for reducing the rebound rate of shotcrete in a tunnel.

[0005] To solve the above technical problems, the technical solution adopted by the present application is as follows: a construction device for reducing the rebound rate of shotcrete in a tunnel, characterized in that it comprises a tunnel initial support mechanism and a rebound reduction mechanism. The tunnel initial support mechanism comprises a plurality of anchor rods spaced apart according to design requirements and penetrating into the rock wall, and a steel mesh arranged in close contact with the rock wall and wrapping the plurality of anchor rods. The outer side of the steel mesh is provided with a plurality of steel arches. The rebound reduction mechanism is arranged between adjacent two steel arches. The rebound reduction mechanism comprises an elastic net arranged between adjacent two steel arches. The outer side of the steel arch is provided with a concrete spraying device.

[0006] The construction device for reducing the rebound rate of shotcrete in a tunnel is characterized in that the inner end of the steel arch is in close contact with the steel mesh.

[0007] The construction device for reducing the rebound rate of shotcrete in a tunnel is characterized in that the steel arch is an H-shaped steel or an I-shaped steel.

[0008] The construction device for reducing the rebound rate of tunnel shotcrete has the characteristics that the inner side of the outer wing plate of the H-shaped steel or I-shaped steel steel arch is fixedly provided with a fixed connecting piece, and the two ends of the elastic net are fixedly connected with the corresponding fixed connecting pieces on the two sides.

[0009] The construction device for reducing the rebound rate of tunnel shotcrete has the characteristics that the elastic net is woven into a grid structure by a plurality of elastic threads, the grid shape of the elastic net includes a square or a triangle, and the side length size of the grid is 2mm-5mm.

[0010] The construction device for reducing the rebound rate of tunnel shotcrete has the characteristics that the elastic thread is a fiber elastic thread, the fiber elastic thread includes one or more of rubber latex thread, polyurethane fiber and synthetic copolymer fiber, thermoplastic polyurethane elastic fiber and polyether ester elastic fiber, the cross-sectional shape of the fiber elastic thread is one or more of a square, a trilobal shape, a Y shape, an L shape, a dumbbell shape, a T shape and a threaded ribbed shape, and the maximum length size of the cross section of the fiber elastic thread is 0.5mm-1mm.

[0011] Meanwhile, the application also discloses a construction method for reducing the rebound rate of tunnel shotcrete, which has the characteristics that the method includes the following steps: Step one, constructing a tunnel primary support mechanism and a rebound reduction mechanism; Step two, preparing concrete and starting the spraying operation by using a concrete spraying device, the concrete in the concrete spraying device is mixed with a quick-setting agent and compressed air, the spraying force generated by the compressed air carries the concrete to start the spraying operation in the operation area between the two adjacent steel arches; Step three, real-time net catching of the sprayed concrete rebound material: When the concrete passes through the elastic net, because the grid side length size of the elastic net is 2mm-5mm and the maximum length size of the cross section of the fiber elastic thread is 0.5mm-1mm, the fine aggregate and cement paste in the concrete directly pass through the elastic net and are directly sprayed onto the rock wall; the coarse aggregate particle size is 5mm-10mm, when passing through the elastic net, because the elastic net has an elastic recovery rate, the coarse aggregate extrudes the elastic net under the action of the spraying force, the grid on the elastic net is deformed under the action of the external force, so that the grid opening becomes larger, so that the coarse aggregate part in the concrete passes through and is directly sprayed onto the rock surface, and then forms a support mechanism with the steel mesh and the anchor rod. When the concrete is sprayed to the working surface, the surface layer separation is caused by the rebound effect, the rebound material mainly composed of coarse aggregate in the concrete is formed, due to the limited thickness of the sprayed layer, the falling distance of the rebound material is short, the gravity acceleration is small, the impact force is not enough to cause the obvious deformation of the elastic net, and the mesh size of the elastic net is smaller than the particle size of the coarse aggregate in the concrete, so the elastic net can effectively constrain the rebound coarse aggregate and bind it in the spraying area to prevent it from falling out of the spraying working area; Step four, the spraying thickness of the sprayed concrete is increased gradually; The sprayed concrete is sprayed with a thickness slightly larger than the thickness of the steel arch, and the construction process of step three is cycled, the spraying thickness of the sprayed concrete is increased gradually, and the sprayed concrete gradually covers the elastic net and the steel arch to form a concrete protective layer wrapping the steel arch, the tunnel primary support mechanism is completely wrapped in the sprayed concrete, and the cross-sectional shape of the fiber elastic wire is one or more of square, three-leaf, Y-shaped, L-shaped, dumbbell-shaped, T-shaped and threaded ribbed, so that the mechanical adhesion between the fiber elastic wire and the concrete is increased, and the fiber elastic wire is integrated with the concrete, when the concrete is subjected to external tension, the elastic net composed of the fiber elastic wire improves the toughness and impact resistance of the concrete; With the completion of the spraying operation in the working area between the two adjacent steel arches, the tunnel primary support mechanism and the rebound reduction mechanism form a complete support whole by means of the sprayed concrete, the rebound rate is reduced when the whole sprayed concrete is operated due to the binding of the elastic net, the fiber elastic wire has a toughening effect, the whole concrete structure is more stable, and a more perfect combined support body is formed; Step five, after the tunnel primary support mechanism and the rebound reduction mechanism are installed in the tunnel length direction as a whole or in segments, the spraying operation is completed, and the construction is completed. Compared with the prior art, the application has the following advantages: 1. The construction device adopted in the application has simple principle, flexible and convenient construction, less new equipment compared with the original process, economically feasible scheme, and is suitable for large-scale popularization and application in the field of tunnel construction; the tunnel primary support mechanism adopts the existing tunnel primary support system, the elastic net with a certain size is arranged outside the spraying operation area; in the spraying process, the concrete extrudes the elastic fiber by means of the impact force of the spraying, so that the mesh expands, the coarse aggregate component passes through smoothly and adheres to the spraying surface; when the concrete rebounds, the rebound material cannot produce enough deformation of the elastic mesh due to the short falling distance, the rebound material can be effectively bound in the working area, the rebound material is captured in real time, so that the overall rebound rate of the sprayed concrete operation is effectively reduced.

[0012] 2, The fiber elastic line contained in the rebound reduction mechanism can be better bonded with the concrete due to the irregular cross section, and when the concrete is subjected to external tension, the fiber elastic line can be deformed with the concrete, and through the efficient absorption and dissipation of impact energy by stretching and deformation, the brittle failure of the concrete structure can be effectively prevented, and the toughness and impact resistance of the concrete can be improved.

[0013] 3, The elastic net in the rebound reduction mechanism can form an elastic network on the surface of the concrete, and the addition of the fiber elastic line can significantly improve the crack resistance of the concrete, in addition, when the concrete is stretched after cracking, the fiber elastic line generates rebound contraction stress on the microcrack, realizes the closure and repair of the microcrack, and further restricts the further expansion of the microcrack, which is beneficial to improve the quality of the concrete.

[0014] 4, The rebound rate of the whole shotcrete operation is reduced, the material waste is greatly reduced, the personnel and mechanical costs of discharging slag are saved, the comprehensive construction cost is greatly reduced, in addition, the shotcrete construction time can be shortened, and the overall construction efficiency can be improved.

[0015] The technical solutions of the present application will be further described in detail below by means of the drawings and examples. DESCRIPTION OF DRAWINGS

[0016] Figure 1 The structure connection schematic diagram of the construction device used in the present application.

[0017] Figure 2 The bottom view of Figure 1 .

[0018] Figure 3 The flow chart of the construction method of the present application.

[0019] Explanation of reference signs: 11 - rock wall; 12 - anchor rod; 13 - steel mesh; 14 - steel arch; 15 - outer wing plate of steel arch; 21 - fixed connecting piece; 22 - elastic net; 23 - elastic line. DETAILED DESCRIPTION

[0020] As Figure 1 and Figure 2As shown, the construction device for reducing rebound rate of tunnel shotcrete in the application comprises a tunnel initial support mechanism and a rebound reduction mechanism, the tunnel initial support mechanism comprises a plurality of anchor rods 12 which are designed to be spaced and penetrated into the rock wall 11, and a reinforcing mesh 13 which is arranged close to the rock wall 11 and wraps the plurality of anchor rods 12, the outer side of the reinforcing mesh 13 is provided with a plurality of steel arches 14, the rebound reduction mechanism is arranged between the adjacent two steel arches 14, the rebound reduction mechanism comprises an elastic mesh 22 which is arranged between the adjacent two steel arches 14, and the outer side of the steel arch 14 is provided with a concrete spraying device.

[0021] It should be noted that the construction device has simple principle, flexible and convenient construction, less new equipment compared with the original process, and the scheme is economic and feasible, which is suitable for large-scale popularization and application in the field of tunnel construction; the tunnel initial support mechanism adopts the existing tunnel initial support system, and the elastic mesh with a certain size is arranged outside the spraying operation area; in the spraying process, the concrete extrudes the elastic fiber by means of the impact force of its own spraying, so that the mesh expands, and the coarse aggregate component successfully passes through and adheres to the spraying surface; when the concrete rebounds, the rebound material cannot produce enough obvious deformation of the elastic mesh due to the short falling distance, and the rebound material can be effectively restrained in the operation area due to the small extension size of the elastic mesh which is smaller than the particle size of the coarse aggregate, so that the rebound material is captured in real time, thereby effectively reducing the overall rebound rate of the shotcrete operation.

[0022] In the embodiment, the inner end of the steel arch 14 is close to the reinforcing mesh 13.

[0023] In the embodiment, the steel arch 14 is H-shaped steel or I-shaped steel.

[0024] In the embodiment, the inner side of the outer wing plate 15 of the H-shaped steel or I-shaped steel steel arch is fixedly provided with a fixed connecting piece 21, and the two ends of the elastic mesh 22 are fixedly connected with the corresponding fixed connecting pieces 21 on the two sides.

[0025] In the embodiment, the elastic mesh 22 is woven into a grid structure by a plurality of elastic wires 23, the grid shape of the elastic mesh 22 comprises a square or a triangle, and the side length size of the grid is 2mm-5mm.

[0026] In the embodiment, the elastic wire 23 is a fiber elastic wire, the fiber elastic wire comprises one or more of rubber latex filament, polyurethane fiber and synthetic copolymer fiber, thermoplastic polyurethane elastic fiber and polyether ester elastic fiber, the cross-sectional shape of the fiber elastic wire is one or more of square, trilobal, Y-shaped, L-shaped, dumbbell-shaped, T-shaped and threaded ribbed type, and the maximum length size of the cross section of the fiber elastic wire is 0.5mm-1mm.

[0027] It should be noted that the fiber elastic line is a synthetic fiber with a certain elastic recovery rate, which has the characteristics of high elongation and high elastic recovery rate. It can deform under external force impact without breaking, and when the external force is small, its small deformation can be ignored. The addition of the elastic net significantly reduces the rebound of the rebound material during the spraying process, thereby effectively reducing the rebound rate during the overall spraying operation.

[0028] As shown in Figure 3 a construction method for reducing the rebound rate of tunnel sprayed concrete, comprising the following steps: Step one, construction of tunnel primary support mechanism and rebound reduction mechanism; Step two, prepare the concrete and start the spraying operation using the concrete spraying equipment. The concrete, quick-setting agent and compressed air are mixed in the concrete spraying equipment. The blowing force generated by the compressed air carries the concrete to the work area between the two adjacent steel arches 14 to start the spraying operation; Step three, real-time net capture of sprayed concrete rebound material: When the concrete passes through the elastic net 22, the fine aggregate and cement paste in the concrete directly pass through the elastic net and are directly sprayed onto the rock wall because the grid edge length size of the elastic net is 2mm-5mm, and the maximum length size of the cross section of the fiber elastic line is 0.5mm-1mm. The coarse aggregate particle size is 5mm-10mm. When it passes through the elastic net 22, the coarse aggregate is extruded by the elastic net 22 under the action of the blowing force due to the elastic recovery rate of the elastic net. The grid on the elastic net deforms under the action of external force, making the grid opening larger, so that the coarse aggregate part in the concrete passes through and is directly sprayed onto the rock surface, and then forms a support mechanism with the steel mesh 13 and the anchor rod 12; When the concrete is sprayed to the work surface, the surface layer separates due to the rebound effect, forming a rebound material mainly composed of coarse aggregate in the concrete. Due to the limited thickness of the construction spraying layer, the falling distance of the rebound material is short, the gravitational acceleration is small, and the impact force generated is not enough to cause significant deformation of the elastic net 22. At the same time, the grid size of the elastic net 22 is smaller than the particle size of the coarse aggregate in the concrete, and the elastic net can effectively constrain the rebounded coarse aggregate and bind it within the spraying area to prevent it from falling out of the spraying operation area; Step four, increase the thickness of the sprayed concrete: The sprayed concrete is sprayed with a thickness slightly greater than the thickness of the steel arch, and the construction process of step three is cycled, the sprayed concrete is sprayed with a thickness gradually increasing, and gradually covers the elastic net 22 and the steel arch 14, forming a concrete protective layer wrapping the steel arch 14, the tunnel primary support mechanism is completely wrapped inside the sprayed concrete, and the cross-sectional shape of the fiber elastic line is one or more of a square, a trilobal shape, a Y shape, an L shape, a dumbbell shape, a T shape, and a threaded ribbed shape, so that the mechanical adhesion between the fiber elastic line and the concrete is increased, and the fiber elastic line is integrated with the concrete; when the concrete is subjected to external tension, the elastic net composed of the fiber elastic line improves the toughness and impact resistance of the concrete; With the completion of the spraying operation in the working area between the two adjacent steel arches 14, the tunnel primary support mechanism and the rebound reduction mechanism form a complete support whole by means of the sprayed concrete, and the rebound rate is reduced during the whole sprayed concrete operation due to the restraint of the elastic net, the fiber elastic line has a toughening effect, the whole concrete structure is more stable, and a more perfect combined support body is formed. Step five, after the tunnel primary support mechanism and the rebound reduction mechanism are installed in the tunnel length direction as a whole or in segments and the spraying operation is completed, the steps one to four are cycled multiple times, until the construction is completed.

[0029] When the invention is used, the fiber elastic line contained in the rebound reduction mechanism can be better bonded with the concrete as a whole due to its irregular cross section, when the concrete is subjected to external tension, the fiber elastic line can be deformed with the concrete, impact energy can be efficiently absorbed and dissipated through stretching and deformation, concrete structure brittle failure can be effectively prevented, and the toughness and impact resistance of the concrete can be improved; the elastic net in the rebound reduction mechanism can form an elastic network on the surface of the concrete, and the addition of the fiber elastic line can significantly improve the crack resistance of the concrete, in addition, when the concrete is stretched after cracking, the fiber elastic line generates rebound contraction stress on the microcracks, realizes the closure and repair of the microcracks, and further restricts the further expansion of the microcracks, which is beneficial to improve the quality of the concrete; by reducing the rebound rate during the whole sprayed concrete operation, material waste is greatly reduced, personnel and mechanical costs such as discharging are saved, and the comprehensive construction cost is greatly reduced, in addition, the spraying support construction time can be shortened, and the overall construction efficiency is improved The above is only a preferred embodiment of the present application, and does not limit the present application, any simple modification, change and equivalent structure change according to the technical essence of the present application to the above embodiment are still within the protection scope of the technical solution of the present application.

Claims

1. A construction device for reducing the rebound rate of shotcrete in tunnels, characterized in that: The tunnel includes an initial support mechanism and a rebound mechanism. The initial support mechanism includes multiple anchor rods (12) that are spaced out into the rock wall (11) according to design requirements, and a steel mesh (13) that is arranged close to the rock wall (11) and wraps around the multiple anchor rods (12). Multiple steel arch frames (14) are set on the outside of the steel mesh (13). A rebound mechanism is set between two adjacent steel arch frames (14). The rebound mechanism includes an elastic net (22) set between two adjacent steel arch frames (14). A concrete spraying device is set on the outside of the steel arch frame (14).

2. A construction device for reducing the rebound rate of shotcrete in tunnels according to claim 1, characterized in that: The inner end of the steel arch frame (14) is tightly attached to the steel mesh (13).

3. A construction device for reducing the rebound rate of shotcrete in tunnels according to claim 1, characterized in that: The steel arch frame (14) is an H-beam or an I-beam.

4. A construction device for reducing the rebound rate of shotcrete in tunnels according to claim 3, characterized in that: The inner side of the outer wing plate (15) of the H-beam or I-beam steel arch frame is fixedly provided with a fixing connector (21), and the two ends of the elastic net (22) are respectively fixedly connected to the corresponding fixing connectors (21) on both sides.

5. A construction device for reducing the rebound rate of shotcrete in tunnels according to claim 1, characterized in that: The elastic net (22) is woven from several elastic threads (23) into a mesh structure. The mesh shape of the elastic net (22) includes squares or triangles, and the side length of the mesh is 2mm to 5mm.

6. A construction device for reducing the rebound rate of shotcrete in tunnels according to claim 5, characterized in that: The elastic thread (23) is a fiber elastic thread, which includes one or more of natural latex filaments, polyurethane fibers and synthetic copolymer fibers, thermoplastic polyurethane elastic fibers, and polyether ester elastic fibers; the cross-sectional shape of the fiber elastic thread is one or more of square, trefoil, Y-shaped, L-shaped, dumbbell-shaped, T-shaped, and threaded ribbed type; the maximum length dimension of the cross-section of the fiber elastic thread is 0.5mm to 1mm.

7. A construction method for reducing the rebound rate of shotcrete in tunnels using the construction device as described in claim 6, characterized in that: The method includes the following steps: Step 1: Initial support structure and rebound mechanism for the construction tunnel; Step 2: Prepare concrete and start spraying operation using concrete spraying equipment. In the concrete spraying equipment, concrete, quick-setting agent and compressed air are mixed. The spraying force generated by the compressed air carries the concrete to the working area between two adjacent steel arch frames (14) to start spraying operation. Step 3: Real-time netting of shotcrete rebound material: When the concrete passes through the elastic mesh (22), since the side length of the mesh on the elastic mesh is 2mm to 5mm and the maximum cross-sectional length of the fiber elastic line is 0.5mm to 1mm, the fine aggregate and cement paste in the concrete pass directly through the elastic mesh and are directly sprayed onto the rock wall; the coarse aggregate has a particle size of 5mm to 10mm. When it passes through the elastic mesh (22), since the elastic mesh has an elastic recovery rate, the coarse aggregate is squeezed by the spraying force. The mesh on the elastic mesh is deformed under the action of external force, which makes the mesh opening larger. Thus, part of the coarse aggregate in the concrete passes through and is directly sprayed onto the rock surface, thereby forming a support structure with the steel mesh (13) and anchor rods (12). When concrete is sprayed onto the working surface, the surface layer separates due to the rebound effect, forming a rebound material mainly composed of coarse aggregate in the concrete. Due to the limited thickness of the sprayed layer, the rebound material falls a short distance and has a small gravitational acceleration, so the impact force generated is insufficient to cause significant deformation of the elastic net (22). At the same time, the mesh size of the elastic net (22) is smaller than the particle size of the coarse aggregate in the concrete. The elastic net can effectively constrain the rebounded coarse aggregate, keeping it within the sprayed area and preventing it from falling off the sprayed working area. Step 4: Gradually increase the thickness of the sprayed concrete: The thickness of the shotcrete is slightly greater than that of the rigid arch frame. The construction process of step three is repeated. The thickness of the shotcrete is gradually increased and gradually covers the elastic net (22) and the steel arch frame (14), forming a concrete protective layer that wraps the steel arch frame (14). The tunnel initial support structure is completely wrapped inside the shotcrete. Since the cross-sectional shape of the fiber elastic line is one or more of square, trilobal, Y-shaped, L-shaped, dumbbell-shaped, T-shaped, and threaded ribbed type, it can increase the mechanical adhesion between it and the concrete, thus combining with the concrete as one. When the concrete is subjected to external tensile force, the elastic net composed of fiber elastic lines improves the toughness and impact resistance of the concrete. With the completion of the shotcreting operation in the working area between two adjacent steel arch frames (14), the tunnel initial support mechanism and the rebound mechanism form a complete support whole with the help of shotcreting. Due to the elastic net binding, the rebound rate during the overall shotcreting operation is reduced. The toughening effect of the fiber elastic line makes the overall concrete structure more stable, forming a more perfect joint support body. Step 5: Repeat steps 1 to 4 multiple times, install the tunnel initial support mechanism and rebound mechanism as a whole or in sections along the tunnel length, and complete the spraying operation until the construction is completed.

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