A shotcrete hanging test device for tunnel rock burst flexible net

Abstract

The application discloses a shotcrete hanging test device for a flexible net in a tunnel rock burst, which comprises a device frame, a lateral support structure, a flexible protective net, a concrete automatic spraying mechanism and a shotcrete collecting groove; the top of the device frame is used for supporting a top arc surface steel plate, and a layer of arc surface concrete is sprayed on the bottom arc surface of the top arc surface steel plate; the lateral support structure is used for blocking the front and back sides and the left and right sides of the device frame, so that the re-sprayed concrete is prevented from being accidentally sprayed outside the test device; the flexible protective net is laid on the lower surface of the arc surface concrete layer; the concrete automatic spraying mechanism is arranged at the bottom of the device frame and is used for re-spraying the concrete on the coverage range of the flexible protective net; and the shotcrete collecting groove is used for collecting the concrete which fails to be hung. The application solves the technical problem that the flexible protective net laid in a rock burst tunnel is easy to cause the shotcrete to be difficult to be hung, and provides a reference basis for obtaining the best laying process of the flexible protective net.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to a test device for shotcrete grouting in tunnel rockburst flexible netting. Background Technology

[0002] During the construction of railway tunnels, the stability of tunnel excavation is affected by complex geological environments. Among these, under high ground stress conditions, the dynamic instability induced by the unloading of brittle hard rock after excavation—known as rockburst—seriously affects the safe construction of tunnels and poses significant risks to life and property. To ensure tunnel excavation stability, rock mass support, as the most direct and effective rockburst prevention measure after underground cavern excavation, has received increasing attention. Most studies are based on the anchor-protective net-shotcrete (anchor-net-shotcrete) support system, continuously improving the rockburst prevention performance of the support system.

[0003] Flexible protective netting, as an emerging polymer material, is made from polymer filament fibers and advanced coating technology. It possesses high strength and toughness, acting as a flexible buffer and energy release mechanism in rockburst protection, making it highly beneficial for preventing rockburst disasters in tunnels. While flexible protective netting offers these advantages, further research is needed into the collaborative construction techniques between this material and other support structures in tunnels to achieve safe, efficient, and economical results.

[0004] During tunnel construction, the flexible protective netting at the anchor bolt fixing points adheres well to the rock surface. However, its low hardness causes the netting material far from the anchor bolts to sag naturally due to gravity. This makes it difficult for subsequent shotcrete to adhere to the netting, resulting in large-scale shotcrete fall-off, significant waste of materials, and extended construction time. This phenomenon is not present in traditional metal protective netting.

[0005] In summary, it is necessary to develop a device to test and analyze the laying methods of flexible protective nets in tunnels, and to test and compare the laying effects of nets of different materials and sizes, so as to obtain the laying method and net material parameters that are most conducive to tunnel construction. Summary of the Invention

[0006] The purpose of this invention is to provide a shotcrete grouting test device for tunnel rockburst flexible nets, so as to solve the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] This invention provides a shotcrete grouting test device for a flexible rockburst net in a tunnel, comprising a device frame, a lateral support structure, a flexible protective net, an automatic concrete spraying mechanism, and a shotcrete collection trough.

[0009] The top of the device frame is used to support the top arc-shaped steel plate, and a layer of arc-shaped concrete is sprayed on the bottom arc surface of the top arc-shaped steel plate.

[0010] The lateral support structure is used to block the front, rear, left and right sides of the device frame to prevent the sprayed concrete from being accidentally sprayed outside the test device.

[0011] The flexible protective netting is laid on the lower surface of the curved concrete layer;

[0012] The automatic concrete spraying mechanism is located at the bottom of the device frame and is used to re-spray concrete within the coverage area of ​​the flexible protective net.

[0013] The shotcrete collection trough is located at the bottom of the automatic shotcrete mechanism and is used to collect concrete that fails to adhere to the slurry.

[0014] Preferably, the device frame is a load-bearing structure welded from multiple rectangular steel bars, including four load-bearing columns and four load-bearing beams respectively connecting the top and bottom of the four load-bearing columns. The bottom of the four top load-bearing beams is welded with four diagonal beams, and the bottom of the four diagonal beams is connected to the top arc-shaped steel plate. The bottom sides of the top arc-shaped steel plate are also supported by two support columns on the two load-bearing beams at the bottom of the load-bearing structure.

[0015] Preferably, the lateral support structure includes a left side baffle and a right side baffle respectively disposed on the left and right sides of the load-bearing structure, and further includes front and rear baffles disposed on the front and rear sides of the load-bearing structure that can be opened or closed laterally from the middle. The front and rear sides of the load-bearing structure are respectively provided with two front and rear baffles. The two front front and rear baffles are slidably connected to the baffle grooves disposed on the front side of the left side baffle and the right side baffle, respectively. The two rear front and rear baffles are slidably connected to the baffle grooves disposed on the rear side of the left side baffle and the right side baffle, respectively.

[0016] Preferably, the flexible protective net is laid on the lower surface of the arc-shaped concrete layer by means of threaded anchor rods and anchoring components. At each position of the threaded anchor rod, a square shim is used to fix the flexible protective net. First, the mesh of the flexible protective net is passed through the threaded anchor rod, then the shim is passed through the threaded anchor rod, and finally the anchor rod matching nut is tightened so that the flexible protective net and the shim are in close contact with the lower surface of the arc-shaped concrete layer.

[0017] Preferably, the automatic concrete spraying mechanism includes a slide rail, a slide table, and a concrete spraying head. The concrete spraying head is rotatably connected to the top of the slide table and is driven by a motor to swing left and right. The slide table is slidably connected to the slide rail and is driven by a linear motor to move back and forth along the slide rail. The front and rear sides of the slide rail are fixed to the two supporting beams on the front and rear sides of the bottom of the supporting structure.

[0018] Preferably, the shotcrete collection trough is located below the supporting beam at the bottom of the supporting structure, and the shotcrete collection trough is movable so that it can be placed into the bottom of the supporting structure or pulled out from the bottom of the supporting structure.

[0019] The present invention achieves the following beneficial technical effects compared to the prior art:

[0020] This invention provides a shotcrete grouting test device for flexible rockburst netting in tunnels. It recreates the laying process of the flexible protective netting at the most unfavorable tunnel arch location, allowing for the investigation of the optimal anchor-net shotcrete construction process suitable for flexible protective netting within tunnels. It also helps obtain the optimal netting material parameters for anchor-net shotcrete construction in tunnels, avoiding the problem of difficult shotcrete grouting on-site. This test device is highly targeted, focusing on the most unfavorable arch location within the tunnel, avoiding testing the entire tunnel cross-section, thus saving significant testing costs and materials. Its reusability also gives it the advantages of being green, low-carbon, and energy-efficient. Furthermore, the method of collecting failed grouting concrete to measure the grouting effect is simple and effective. Combined with its simple device structure, this test device is scientifically effective, structurally simple, and easy to operate. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the sprayed concrete grouting test device used for tunnel rockburst flexible netting in this invention;

[0023] Figure 2 This is a schematic diagram of the structure of the device frame and the automatic concrete spraying mechanism in this invention;

[0024] Figure 3 This is a bottom view of the top arc-shaped steel plate in this invention;

[0025] Figure 4 This is a partial structural diagram of the flexible protective netting fixed by anchor bolts in this invention;

[0026] Figure 5 This is a schematic diagram of the lateral support structure in this invention;

[0027] In the diagram: 1. Device frame; 1-1. Load-bearing structure; 1-1a. Load-bearing column; 1-1b. Load-bearing beam; 1-1c. Inclined beam; 1-1d. Support column; 1-2. Top curved steel plate; 1-3. Curved concrete layer; 1-4. Circular hole in the top plate; 2. Lateral support structure; 2-1. Left side baffle; 2-2. Right side baffle; 2-3. Front and rear baffle slide grooves; 2-4. Front and rear baffles; 3. Flexible protective net; 4. Threaded anchor bolt; 5. Anchoring components; 5-1. Washer; 5-2. Anchor bolt matching nut; 6. Automatic concrete spraying mechanism; 6-1. Slide rail; 6-2. Slide table; 6-3. Concrete spraying head; 7. Sprayed concrete collection trough. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The purpose of this invention is to provide a shotcrete grouting test device for tunnel rockburst flexible nets, in order to solve the problems existing in the prior art.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] The shotcrete grouting test device for tunnel rockburst flexible mesh in this embodiment, such as Figures 1-5 As shown, it includes a device frame 1, a lateral support structure 2, a flexible protective net 3, an automatic concrete spraying mechanism 6, and a sprayed concrete collection trough 7.

[0032] The top of the device frame 1 is used to support the top arc-shaped steel plate 1-2, and a layer of arc-shaped concrete 1-3 is sprayed on the bottom arc surface of the top arc-shaped steel plate 1-2.

[0033] The lateral support structure 2 is used to block the front, rear and left and right sides of the device frame 1 to prevent the sprayed concrete from accidentally being sprayed outside the test device.

[0034] Flexible protective netting 3 is laid on the lower surface of the curved concrete layer 1-3;

[0035] The automatic concrete spraying mechanism 6 is located at the bottom of the device frame 1 and is used to re-spray concrete over the area covered by the flexible protective net 3.

[0036] The shotcrete collection tank 7 is located at the bottom of the automatic shotcrete mechanism 6 and is used to collect concrete that fails to adhere properly.

[0037] In this specific embodiment, the device frame 1 is a load-bearing structure 1-1 welded from multiple rectangular steel bars, including four load-bearing columns 1-1a and four load-bearing beams 1-1b connecting the top and bottom of the four load-bearing columns 1-1a respectively. At the four corners of the bottom of the four load-bearing beams 1-1b at the top, four inclined beams 1-1c are welded. The bottom of the four inclined beams 1-1c is connected to the top arc-shaped steel plate 1-2. The bottom sides of the top arc-shaped steel plate 1-2 are also supported on the two load-bearing beams 1-1b at the bottom of the load-bearing structure 1-1 by two support columns 1-1d.

[0038] In this specific embodiment, the lateral support structure 2 includes a left baffle 2-1 and a right baffle 2-2 respectively disposed on the left and right sides of the bearing structure 1-1, and also includes front and rear baffles 2-4 disposed on the front and rear sides of the bearing structure 1-1 that can be opened or closed laterally from the middle. The bearing structure 1-1 has two front and rear baffles 2-4 respectively disposed on the front and rear sides. The two front front and rear baffles 2-4 are slidably connected to the baffle grooves disposed on the front side of the left baffle 2-1 and the right baffle 2-2, respectively. The two rear front and rear baffles 2-4 are slidably connected to the baffle grooves disposed on the rear side of the left baffle 2-1 and the right baffle 2-2, respectively.

[0039] In this specific embodiment, the flexible protective net 3 is laid on the lower surface of the arc-shaped concrete layer 1-3 through threaded anchor rods 4 and anchoring components 5. At each position of the threaded anchor rod 4, a square gasket 5-1 is used to fix the flexible protective net 3. First, the mesh of the flexible protective net 3 is passed through the threaded anchor rod 4, then the gasket 5-1 is passed through the threaded anchor rod 4, and finally the anchor rod matching nut 5-2 is tightened so that the flexible protective net 3 and the gasket 5-1 are tightly attached to the lower surface of the arc-shaped concrete layer 1-3.

[0040] In this specific embodiment, the automatic concrete spraying mechanism 6 includes a slide rail 6-1, a slide table 6-2, and a concrete spraying head 6-3. The concrete spraying head 6-3 is rotatably connected to the top of the slide table 6-2 and is driven by a motor to swing left and right. The slide table 6-2 is slidably connected to the slide rail 6-1 and is driven by a linear motor to move back and forth along the slide rail 6-1. The front and rear sides of the slide rail 6-1 are fixed to the two supporting beams 1-1b on the front and rear sides of the bottom of the supporting structure 1-1.

[0041] In this specific embodiment, the shotcrete collection trough 7 is located below the bottom supporting beam 1-1b of the supporting structure 1-1. The shotcrete collection trough 7 is movably arranged so that it can be placed into the bottom of the supporting structure 1-1 or pulled out from the bottom of the supporting structure 1-1.

[0042] The construction steps of the shotcrete grouting test device for tunnel rockburst flexible mesh in this invention are as follows:

[0043] (1) Building the framework

[0044] Since the location of the tunnel arch is the least suitable for hanging flexible protective netting 3, the test device is used to simulate the construction process of the tunnel arch. The main body of the test device is a cuboid, and the main body of the test construction surface is a prefabricated arc-shaped steel plate. The load-bearing column 1-1a and the load-bearing beam 1-1b are welded to form a load-bearing mechanism, and then the arc-shaped steel plate and the load-bearing structure 1-1 are connected as a whole.

[0045] (2) Initial shotcrete application and installation of anchor bolts

[0046] A layer of curved concrete is initially sprayed onto the lower surface of the top curved steel plate 1-2 to restore the rock surface at the arch crown after the smooth blasting excavation of the tunnel. After the initial sprayed concrete has solidified, anchor bolt positions are located on the upper surface of the top curved steel plate 1-2. Subsequently, a circular hole 1-4 is drilled at each anchor bolt position, with the circular hole 1-4 vertically penetrating the top curved steel plate 1-2 and the curved concrete layer 1-3. A threaded anchor bolt 4 is installed in each circular hole, with a section of bolt protruding downwards after passing through the hole. Each threaded anchor bolt 4 is perpendicular to the top curved steel plate 1-2 at its installation position.

[0047] (3) Lateral support structure 2

[0048] To evaluate the grout adhesion rate of the second sprayed concrete, a sprayed concrete collection trough was placed at the bottom of the test apparatus. A left-side baffle 2-1 and a right-side baffle 2-2 were also added. Eight front and rear baffle grooves 2-3 were arranged on the left-side and right-side baffles 2-1 and 2-2, divided into upper and lower groups. These grooves were used to fix four front and rear baffles 2-4 and to support the sliding of the baffles 2-4 left and right on the grooves 2-3. When the front and rear baffles 2-4 were open, they facilitated manual mesh laying or post-test cleaning of the apparatus. When closed, the front and rear baffles 2-4, together with the left-side and right-side baffles 2-1, prevented accidental spraying of the second sprayed concrete outside the test apparatus, increasing test safety and improving the accuracy of the test data.

[0049] (4) Hang flexible protective netting 3

[0050] The flexible protective netting 3 used in the experiment was laid on the lower surface of the curved concrete layer 1-3. A square washer 5-1 was used to fix the flexible protective netting 3 at each threaded anchor rod 4 position. First, the mesh of the flexible protective netting 3 was passed through the threaded anchor rod 4. Then, the washer 5-1 was passed through the threaded anchor rod 4. Finally, the anchor rod nut 5-2 was tightened, ensuring that the flexible protective netting 3 and the washer 5-1 were tightly attached to the lower surface of the curved concrete layer 1-3. Using this fixing method, starting from the left row of threaded anchor rods 4, the netting was laid row by row along the circumference, left, center, and right. Each threaded anchor rod 4 was fixed individually in each row. Before each fixing, it was ensured that the flexible protective netting 3 was maximally attached to the lower surface of the curved concrete layer 1-3 to avoid significant bulging.

[0051] (5) Sprayed concrete

[0052] After the entire flexible protective net 3 is laid, the front and rear baffles 2-4 are slid to close the baffles. The automatic concrete spraying mechanism 6 then sprays concrete over the area covered by the flexible protective net 3. The concrete spraying head, connected to the shotcrete mix, is mounted on a sliding table 6-2 and swings left and right on the table. The sliding table 6-2 moves back and forth along the slide rail 6-1. The movement and swinging of the automatic concrete spraying mechanism 6 are manually controlled by a control system to ensure even spraying of concrete onto the flexible protective net 3. After reaching the designed spraying volume, the remaining shotcrete on the lateral support structure 2 is removed into the shotcrete collection trough. The collection trough is then removed, and the mass of the shotcrete that failed to adhere is weighed to measure the adhesion effect.

[0053] This invention has illustrated its principles and implementation methods using specific examples. The descriptions of these embodiments are merely illustrative of the method and its core ideas; furthermore, those skilled in the art will recognize that modifications may be made to the specific implementation methods and application scope based on the principles of this invention. Therefore, the content of this specification should not be construed as limiting the invention.

Claims

1. A test device for shotcrete grouting in tunnel rockburst flexible mesh, characterized in that: The device includes a frame, lateral support structures, a flexible protective net, an automatic concrete spraying mechanism, and a shotcrete collection trough. The top of the frame supports a top curved steel plate, on which a layer of curved concrete is sprayed. The lateral support structures block the front, rear, left, and right sides of the frame, preventing accidental spraying of re-sprayed concrete outside the testing area. The flexible protective net is laid on the lower surface of the curved concrete layer. The automatic concrete spraying mechanism is located at the bottom of the frame and is used to re-spray concrete within the area covered by the flexible protective net. The shotcrete collection trough is located at the bottom of the automatic concrete spraying mechanism and is used to collect concrete that has failed to adhere properly.

2. The shotcrete grouting test device for tunnel rockburst flexible mesh according to claim 1, characterized in that: The device frame is a load-bearing structure welded from multiple rectangular steel bars, including four load-bearing columns and four load-bearing beams connecting the top and bottom of the four load-bearing columns respectively. The bottom of the four top load-bearing beams is welded with four diagonal beams, and the bottom of the four diagonal beams is connected to the top arc-shaped steel plate. The bottom sides of the top arc-shaped steel plate are also supported by two support columns on the two load-bearing beams at the bottom of the load-bearing structure.

3. The shotcrete grouting test device for tunnel rockburst flexible mesh according to claim 2, characterized in that: The lateral support structure includes a left side baffle and a right side baffle respectively disposed on the left and right sides of the load-bearing structure, and also includes front and rear baffles disposed on the front and rear sides of the load-bearing structure that can be opened or closed laterally from the middle. The front and rear sides of the load-bearing structure are respectively provided with two front and rear baffles. The two front baffles are slidably connected to the baffle grooves disposed on the front side of the left side baffle and the right side baffle, respectively. The two rear baffles are slidably connected to the baffle grooves disposed on the rear side of the left side baffle and the right side baffle, respectively.

4. The shotcrete grouting test device for tunnel rockburst flexible mesh according to claim 1, characterized in that: The flexible protective net is laid on the lower surface of the arc-shaped concrete layer through threaded anchor rods and anchoring components. At each location of the threaded anchor rod, a square shim is used to fix the flexible protective net. First, the mesh of the flexible protective net is passed through the threaded anchor rod, then the shim is passed through the threaded anchor rod, and finally the anchor rod matching nut is tightened so that the flexible protective net and the shim are in close contact with the lower surface of the arc-shaped concrete layer.

5. The shotcrete grouting test device for tunnel rockburst flexible mesh according to claim 2, characterized in that: The automatic concrete spraying mechanism includes a slide rail, a slide table, and a concrete spraying head. The concrete spraying head is rotatably connected to the top of the slide table and is driven by a motor to swing left and right. The slide table is slidably connected to the slide rail and is driven by a linear motor to move back and forth along the slide rail. The front and rear sides of the slide rail are fixed to the two supporting beams on the front and rear sides of the bottom of the supporting structure.

6. The shotcrete grouting test device for tunnel rockburst flexible mesh according to claim 2, characterized in that: The shotcrete collection trough is located below the supporting beam at the bottom of the supporting structure. The shotcrete collection trough is movable and can be placed into or pulled out from the bottom of the supporting structure.

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