Anti-shearing supporting system and method for soft composite roof of flexible formwork gob-side entry retaining

Abstract

The invention discloses an anti-shearing supporting system for a soft composite roof of a flexible formwork gob-side entry retaining. The anti-shearing supporting system comprises an advanced working face grouting supporting structure, a flexible net laid in front of an end support, a rhombic metal net additionally arranged behind the end support, a supplementary anchor rod and a steel plate, wherein the supplementary anchor rod and the steel plate are used for fixing the rhombic metal net and reinforcing a to-be-poured space roof. According to the anti-shearing supporting system for the soft composite roof of the flexible formwork gob-side entry retaining, the problem that under disturbance of large-mining-height mining-induced stress, the roof of an entry retaining wall is prone to shearing is solved.

Description

Technical Field

[0001] This invention belongs to the field of coal mine gob-side roadway support technology, specifically relating to a shear-resistant support system for soft composite roofs in flexible gob-side roadways, and also relating to a shear-resistant support method for soft composite roofs in flexible gob-side roadways. Background Technology

[0002] High-extraction fully mechanized mining technology has become one of the core technologies for the efficient development of thick coal seams due to its advantages such as improved mining efficiency, reduced roadway excavation, and lower excavation rate per 10,000 tons. Goaf retention, a key technology in high-extraction longwall mining, uses the haulage roadway (or return air roadway) of the previous working face as the mining roadway for the next working face. This reduces roadway excavation, increases resource recovery, and effectively alleviates the problem of tight mining continuity, making it an important supporting technology for green mining and intelligent transformation of coal mines.

[0003] However, under high-extraction mining conditions, the basic roof cycle pressure step distance and dynamic load coefficient increase significantly. Furthermore, the "weak composite roof" characteristic—comprising multiple layers of weakly cemented, low-strength rock strata such as mudstone, sandy mudstone, and thin-layered limestone—is particularly problematic due to well-developed bedding fractures, poor overall integrity, and weak self-stabilizing ability. Under high-extraction mining dynamic stress disturbances, this type of roof is prone to shearing of the roadway wall roof, hindering the widespread application of roadway retention technology along the goaf at high extraction heights. Therefore, to address the problem of shearing of the roadway wall roof in weak composite roofs at roadway retention faces, a new support method is proposed. This method achieves precise shear-resistant design through anchoring, lateral collaborative force transmission to form an integral shear-resistant layer, and adapts to asymmetric pressure, fundamentally improving the roof's shear resistance. Summary of the Invention

[0004] The first objective of this invention is to provide a shear-resistant support system for weak composite roofs in flexible formwork roadways, which solves the problem of roof shearing in roadway walls under mining stress disturbances at high mining heights.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a shear protection system for soft composite roof slabs in flexible formwork goaf-retention tunnels, including an advanced working face grouting support structure, a flexible mesh laid in front of the end support frame, a diamond-shaped metal mesh added behind the end support frame, anchor bolts and steel plates for fixing the diamond-shaped metal mesh and for reinforcing the roof slab to be poured.

[0006] The technical solution of the present invention also has the following characteristics:

[0007] The advanced working face grouting support structure is constructed by using an anchor cable drilling rig to drive hollow grouting anchor cables perpendicular to the top plate within a range of no less than 80m from the advanced working face.

[0008] The hollow grouting anchor cables are installed in two rows along the longitudinal direction of the roadway. The distance between the first row and the first backfill side is 550-650mm, and the distance between the second row and the first row is 1800-2200mm; the spacing is 1800-2200mm.

[0009] The advanced working face grouting support structure shall carry out grouting reinforcement of the top plate within a range of not less than 20m of the advanced working face.

[0010] The material used for roof grouting is silicate-modified polyurethane material for reinforcing coal and rock in coal mines.

[0011] One side of the diamond-shaped metal mesh extends 300-500mm beyond the goaf side of the flexible concrete wall, while the other side extends into the roadway.

[0012] The anchor bolts used for the replacement are threaded steel anchor bolts, which are installed along both sides of the flexible concrete wall.

[0013] The second objective of this invention is to provide a method for shear protection of weak composite roof in flexible formwork roadway retention, ensuring the stability of the surrounding rock in the working space during roadway retention and guaranteeing the safety of construction personnel in the working space.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is: a method for shear protection of weak composite roof slabs along flexible formwork in tunnels, comprising: Step 1: Drill grouting holes at the advanced working face and install hollow grouting anchor cables; Step 2: As the working face is mined, the roof of the roadway is reinforced by grouting using hollow grouting anchor cables; Step 3: As the working face advances, a flexible net is laid in front of the end support frame; Step 4: Lay a diamond-shaped metal mesh underneath the flexible mesh; Step 5: After laying the diamond-shaped metal mesh, drill additional anchor bolt holes, install additional anchor bolts in the additional anchor bolt holes, and support the steel plate with the anchor bolt tray; Step 6: After the formwork is installed by the formwork hanging device, concrete pouring begins. Afterward, the formwork hanging device is removed from the formwork and moves forward with the workpiece. Step 7: Repeat steps 1-6 until the entire working face is left open.

[0015] The technical solution of the present invention also has the following characteristics: In step 1: In order to prevent the shearing effect of the flexible concrete wall on the roof in the roadway, hollow grouting anchors are installed in an area of ​​no less than 80m ahead of the working face, i.e., the area where hollow grouting anchors are installed. The hollow grouting anchors are installed in two rows along the longitudinal direction of the roadway. The distance between the first row of hollow grouting anchors and the primary mining side is 500-700mm. The distance between the second row and the secondary mining side is 2600-3000mm. The distance between the two rows of hollow grouting anchors is 1800-2200mm. The distance between adjacent hollow grouting anchors in the same row is 1800-2200mm.

[0016] In step 2: the grouting material is silicate-modified polyurethane material for coal mine reinforcement, the grouting pressure is not less than 3MPa, the grout wraps the anchor cable and fills the cracks in the roof rock layer, forming a stable structure in the roof.

[0017] The beneficial effects of this invention are as follows: The shear protection support system and method for weak composite roof slabs in flexible formwork gob-side roadway retention of this invention, when performing gob-side roadway retention at the working face, combines advanced hollow grouting anchor cable grouting reinforcement support with the combined shear support of the area to be poured, effectively forming a deep overall shear-resistant structure to suppress rock strata shear displacement, enhance the shear strength and overall stability of the roadway roof, and at the same time, combined with measures to ensure the safety of the roadway during the flexible formwork concrete wall pouring process, significantly reduce the risk of roof shear failure and ensure the safe and reliable reuse of the roadway. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the layout of the flexible formwork-based shear protection system for weak composite roof in the roadway retention face, provided by an embodiment of the present invention. Figure 2 This is a schematic diagram of the cross-section of the hollow grouting anchor cable support in the advanced working face of the flexible formwork roadway weak composite roof anti-shear support system provided in the embodiment of the present invention. Figure 3 This is a schematic diagram of the cross-section of the reinforced support of the space anchor bolt + steel plate combination for the soft composite roof anti-shear support system for flexible formwork along the tunnel provided in the embodiment of the present invention. Figure 4 This is a schematic diagram of a rigid combined support structure for a flexible mold-assisted tunnel-side weak composite roof shear protection system provided in an embodiment of the present invention.

[0019] In the diagram, 1. Retained roadway, 2. Anchor cable, 3. Anchor bolt, 4. Hollow grouting anchor cable, 5. Rigid combined support structure, 6. Replacement anchor bolt, 7. Flexible concrete wall, 8. Goaf, 9. High-strength steel plate, 10. End support, 11. Diamond-shaped metal mesh, 12. Rockfill support, 13. Hollow grouting anchor cable installation area, 14. Hollow grouting anchor cable grouting area, 15. First-stage mining side, 16. Flexible mesh. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] Example 1 During the tunnel excavation process, anchor bolts 3 and anchor cables 2 are used as the basic support for the tunnel. To ensure the safety of the tunnel, an end support 10 is arranged in the working face end area, and a retaining rock support 12 is arranged in the goaf area 8 behind the end support 10 and on the side of the flexible concrete wall 7.

[0022] This invention discloses a flexible formwork roadway retention system for shear protection of weak composite roof. Flexible formwork roadway retention refers to the construction of a continuous flexible formwork wall along the goaf side of the roadway during the mining process, preserving the roadway for use as the roadway for the next working face. The flexible formwork roadway retention system for shear protection of weak composite roof includes advanced working face grouting support, laying flexible mesh 16 in front of the end frame, adding 8# diamond-shaped metal mesh 11 behind the end frame, fixing the 8# diamond-shaped metal mesh 11 with a combination of anchor bolts 6 and high-strength steel plates 9, and reinforcing the roof of the space to be poured, etc., and at the same time improving the flexible formwork concrete wall pouring measures.

[0023] Advanced grouting support involves installing hollow grouting anchor cables 4 at a certain distance ahead of the working face during the mining process, and then using the hollow grouting anchor cables 4 to reinforce the roof of the roadway. Laying flexible netting 16 in front of the end support involves laying a certain width of flexible netting 16 in front of the end support during the roadway construction process, as the working face advances, to protect the roof and ensure that the weak composite roof does not collapse in time after mining, thus guaranteeing the safety of the roadway working space.

[0024] An 8# diamond-shaped metal mesh 11 is added after the end support frame. In order to ensure that the flexible formwork wall does not shear the roof, an additional layer of 8# diamond-shaped metal mesh 11 is added below the existing flexible mesh 16 after the end support frame 10 is erected during the tunneling process. Anchor bolts 6 and high-strength steel plates 9 are added as the working face advances. Anchor bolts 6 are added at the position of the roof of the flexible formwork concrete wall to be poured after the end support frame 10 is erected. The anchor bolts are used to suspend the high-strength steel plates 9. The rigid combined support structure 5 formed by the two is used to fix the 8# diamond-shaped metal mesh 11. At the same time, a rigid combination is formed above the flexible formwork wall to reinforce the roof above the flexible formwork wall and suppress the shearing and settlement deformation of the roof rock strata along the roof of the flexible formwork concrete wall.

[0025] Improve the pouring measures for flexible formwork concrete walls. During the pouring process, strictly implement the pressure-bonding process for flexible formwork concrete walls to ensure that the flexible formwork concrete wall and the roof slab are in surface-to-surface contact, reduce uneven stress, and ensure that the basic requirements of "straight wall, flat surface, and solid roof connection" for flexible formwork concrete walls are met, thus preventing the occurrence of oblique cutting damage to the top flexible formwork wall. At the same time, strengthen the management of materials to ensure that the strength of the flexible formwork concrete wall meets the requirements.

[0026] Example 2 The present invention provides a method for shear protection of weak composite roof slabs in flexible formwork tunnels, which is implemented according to the following steps: Step 1: In the retained roadway, to prevent the flexible concrete wall 7 from shearing the roof, hollow grouting anchor cable 4 holes are drilled perpendicularly to the roof using an anchor cable drilling rig in the area 60m ahead of the working face, i.e., the hollow grouting anchor cable installation area 13. Hollow grouting anchor cable 4 holes are installed. Two rows of hollow grouting anchor cable 4 holes are drilled along the longitudinal direction of the retained roadway. The distance between the first row of hollow grouting anchor cable 4 and the primary mining side 15 is 500mm. The distance between the second row and the secondary mining side is 2600mm. The row spacing of the two rows of hollow grouting anchor cable 4 is 1800mm. The spacing between adjacent hollow grouting anchor cable 4 in the same row is 1800mm. The hollow grouting anchor cable 4 has a specification of φ21.8mm and a length of 9300mm.

[0027] Step 2: As the working face is mined, in an area of ​​no less than 20m ahead of the working face, i.e., the hollow grouting anchor cable grouting area 14, the roof of the roadway is reinforced by grouting using hollow grouting anchor cables 4; the grouting material is silicate modified polyurethane material for coal mine reinforcement, the grouting pressure is no less than 3MPa, the grout wraps the anchor cable and fills the cracks in the roof rock layer, forming a stable structure for the roof.

[0028] Step 3: During the roadway retention process, as the working face advances, a layer of flexible netting 16 needs to be laid in front of the 10th end support frame. The flexible netting 16 is laid in front of the 2nd end support frame towards the tail of the machine, with a width of not less than 10m. One side of the flexible netting extends 500mm into the roadway and is securely tied to the metal mesh on the roof of the roadway, while the other side extends naturally. The length of the flexible netting 16 is consistent with the advance of the working face.

[0029] Step 4: After the end support 10 frames and at the front end of the formwork device, lay another layer of No. 8 diamond-shaped metal mesh 11 below the original flexible mesh 16; one side of the No. 8 diamond-shaped metal mesh 11 extends 300mm beyond the goaf side of the flexible formwork concrete wall, and the other side extends into the roadway; the total width of the No. 8 diamond-shaped metal mesh 11 is 3000mm; the No. 8 diamond-shaped metal mesh 11 and the original roof protection mesh in the roadway are connected with No. 14 rust-proof iron wire through holes to ensure that the mesh is firmly connected.

[0030] Step 5: As the work surface advances, after the end support 10 frames and the front end of the formwork device, lay the No. 8 diamond-shaped metal mesh 11, and then drill anchor bolt holes at certain intervals. After installing the anchor bolts 6 in the anchor bolt holes, use the anchor bolt tray to support a high-strength steel plate. The anchor bolts 6 and the high-strength steel plate 9 form a rigid combined support structure 5, which together fixes the No. 8 diamond-shaped metal mesh 11, and also strengthens the top plate above the flexible formwork concrete wall 7, inhibiting the top rock layer from spreading along the flexible formwork. The top slab of concrete wall 7 underwent shear settlement deformation; the supplementary anchor rods 6 used in the rigid composite support structure 5 are left-hand threaded steel anchor rods, installed along both sides of the flexible formwork concrete wall, with a distance of 150mm from the flexible formwork concrete wall 7, a diameter of φ22mm, and a length of 2500mm; the high-strength steel plate 9 of the rigid composite support structure 5 has a strength of Q235, a length of 1800mm, a width of 300mm, and a thickness of 10mm; holes are drilled on both sides of the high-strength steel plate 9, with a diameter sufficient for anchor rod installation.

[0031] Step 6: Hang the flexible mold using the formwork hanging device. After the flexible mold is hung, start pouring concrete. Once the concrete strength meets the demolding requirements, the formwork hanging device is removed and moves forward with the workpiece.

[0032] Step 7: Repeat steps 1-6 until the entire working face is left open.

[0033] Example 3 The present invention provides a method for shear protection of weak composite roof slabs in flexible formwork tunnels, which is implemented according to the following steps: Step 1: In the retained roadway, to prevent the flexible concrete wall 7 from shearing the roof, hollow grouting anchor cable 4 holes are drilled perpendicularly to the roof using an anchor cable drilling rig in an area 80m ahead of the working face, i.e., the hollow grouting anchor cable installation area 13. Hollow grouting anchor cable 4 holes are installed. Two rows of hollow grouting anchor cable 4 holes are drilled along the longitudinal direction of the retained roadway. The distance between the first row of hollow grouting anchor cable 4 and the primary mining side 15 is 700mm. The distance between the second row and the secondary mining side is 3000mm. The row spacing of the two rows of hollow grouting anchor cable 4 is 2200mm. The spacing between adjacent hollow grouting anchor cable 4 in the same row is 2200mm. The hollow grouting anchor cable 4 has a specification of φ21.8mm and a length of 9300mm.

[0034] Step 2: As the working face is mined, in an area of ​​no less than 20m ahead of the working face, i.e., the hollow grouting anchor cable grouting area 14, the roof of the roadway is reinforced by grouting using hollow grouting anchor cables 4; the grouting material is silicate modified polyurethane material for coal mine reinforcement, the grouting pressure is no less than 3MPa, the grout wraps the anchor cable and fills the cracks in the roof rock layer, forming a stable structure for the roof.

[0035] Step 3: During the roadway retention process, as the working face advances, a layer of flexible netting 16 needs to be laid in front of the 10th end support frame. The flexible netting 16 is laid in front of the 2nd end support frame towards the tail of the machine, with a width of not less than 10m. One side of the flexible netting extends 500mm into the roadway and is securely tied to the metal mesh on the roof of the roadway, while the other side extends naturally. The length of the flexible netting 16 is consistent with the advance of the working face.

[0036] Step 4: After the end support 10 frames and at the front end of the formwork device, lay another layer of No. 8 diamond-shaped metal mesh 11 below the original flexible mesh 16; one side of the No. 8 diamond-shaped metal mesh 11 extends 500mm beyond the goaf side of the flexible formwork concrete wall, and the other side extends into the roadway; the total width of the No. 8 diamond-shaped metal mesh 11 is 3000mm; the No. 8 diamond-shaped metal mesh 11 and the original roof protection mesh in the roadway are connected with No. 14 rust-proof iron wire through holes to ensure that the mesh is firmly connected.

[0037] Step 5: As the work surface advances, after the end support 10 frames and the front end of the formwork device, lay the No. 8 diamond-shaped metal mesh 11, and then drill anchor bolt holes at certain intervals. After installing the anchor bolts 6 in the anchor bolt holes, use the anchor bolt tray to support a high-strength steel plate. The anchor bolts 6 and the high-strength steel plate 9 form a rigid combined support structure 5, which together fixes the No. 8 diamond-shaped metal mesh 11, and also strengthens the top plate above the flexible formwork concrete wall 7, inhibiting the top rock layer from spreading along the flexible formwork. The top slab of concrete wall 7 underwent shear settlement deformation; the supplementary anchor rods 6 used in the rigid composite support structure 5 are left-hand threaded steel anchor rods, installed along both sides of the flexible formwork concrete wall, with a distance of 150mm from the flexible formwork concrete wall 7, a diameter of φ22mm, and a length of 2500mm; the high-strength steel plate 9 of the rigid composite support structure 5 has a strength of Q235, a length of 1800mm, a width of 300mm, and a thickness of 10mm; holes are drilled on both sides of the high-strength steel plate 9, with a diameter sufficient for anchor rod installation.

[0038] Step 6: Hang the flexible mold using the formwork hanging device. After the flexible mold is hung, start pouring concrete. Once the concrete strength meets the demolding requirements, the formwork hanging device is removed and moves forward with the workpiece.

[0039] Step 7: Repeat steps 1-6 until the entire working face is left open.

[0040] Example 4 The present invention provides a method for shear protection of weak composite roof slabs in flexible formwork tunnels, which is implemented according to the following steps: Step 1: In the retained roadway, to prevent the flexible concrete wall 7 from shearing the roof, hollow grouting anchor cable 4 holes are drilled perpendicularly to the roof using an anchor cable drilling rig in the area 70m ahead of the working face, i.e., the hollow grouting anchor cable installation area 13. Hollow grouting anchor cable 4 holes are installed. Two rows of hollow grouting anchor cable 4 holes are drilled along the longitudinal direction of the retained roadway. The distance between the first row of hollow grouting anchor cable 4 and the primary mining side 15 is 600mm. The distance between the second row and the secondary mining side is 2800mm. The row spacing of the two rows of hollow grouting anchor cable 4 is 2000mm. The spacing between adjacent hollow grouting anchor cable 4 in the same row is 2000mm. The hollow grouting anchor cable 4 has a specification of φ21.8mm and a length of 9300mm.

[0041] Step 2: As the working face is mined, in an area of ​​no less than 20m ahead of the working face, i.e., the hollow grouting anchor cable grouting area 14, the roof of the roadway is reinforced by grouting using hollow grouting anchor cables 4; the grouting material is silicate modified polyurethane material for coal mine reinforcement, the grouting pressure is no less than 3MPa, the grout wraps the anchor cable and fills the cracks in the roof rock layer, forming a stable structure for the roof.

[0042] Step 3: During the roadway retention process, as the working face advances, a layer of flexible netting 16 needs to be laid in front of the 10th end support frame. The flexible netting 16 is laid in front of the 2nd end support frame towards the tail of the machine, with a width of not less than 10m. One side of the flexible netting extends 500mm into the roadway and is securely tied to the metal mesh on the roof of the roadway, while the other side extends naturally. The length of the flexible netting 16 is consistent with the advance of the working face.

[0043] Step 4: After the end support 10 frames and at the front end of the formwork hanging device, lay another layer of No. 8 diamond metal mesh 11 below the original flexible mesh 16; one side of No. 8 diamond metal mesh 11 extends 400mm beyond the goaf side of the flexible formwork concrete wall, and the other side extends into the roadway; the total width of No. 8 diamond metal mesh 11 is 3000mm; No. 8 diamond metal mesh 11 and the original roof protection mesh in the roadway are connected with No. 14 rust-proof iron wire through holes to ensure that the mesh is firmly connected.

[0044] Step 5: As the work surface advances, after the end support 10 frames and the front end of the formwork device, lay the No. 8 diamond-shaped metal mesh 11, and then drill anchor bolt holes at certain intervals. After installing the anchor bolts 6 in the anchor bolt holes, use the anchor bolt tray to support a high-strength steel plate. The anchor bolts 6 and the high-strength steel plate 9 form a rigid combined support structure 5, which together fixes the No. 8 diamond-shaped metal mesh 11, and also strengthens the top plate above the flexible formwork concrete wall 7, inhibiting the top rock layer from spreading along the flexible formwork. The top slab of concrete wall 7 underwent shear settlement deformation; the supplementary anchor rods 6 used in the rigid composite support structure 5 are left-hand threaded steel anchor rods, installed along both sides of the flexible formwork concrete wall, with a distance of 150mm from the flexible formwork concrete wall 7, a diameter of φ22mm, and a length of 2500mm; the high-strength steel plate 9 of the rigid composite support structure 5 has a strength of Q235, a length of 1800mm, a width of 300mm, and a thickness of 10mm; holes are drilled on both sides of the high-strength steel plate 9, with a diameter sufficient for anchor rod installation.

[0045] Step 6: Hang the flexible mold using the formwork hanging device. After the flexible mold is hung, start pouring concrete. Once the concrete strength meets the demolding requirements, the formwork hanging device is removed and moves forward with the workpiece.

[0046] Step 7: Repeat steps 1-6 until the entire working face is left open.

[0047] Example 5 The present invention provides a method for shear protection of weak composite roof slabs in flexible formwork tunnels, which is implemented according to the following steps: Step 1: In order to prevent the shearing effect of the flexible concrete wall 7 on the roof in the roadway, hollow grouting anchor cable installation area 13, 60m ahead of the working face, is drilled with an anchor cable drilling rig perpendicular to the roof to install hollow grouting anchor cables 4. Two rows of hollow grouting anchor cable 4 holes are drilled along the longitudinal direction of the roadway. The distance between the first row of hollow grouting anchor cables 4 and the primary mining side 15 is 700mm. The distance between the second row and the secondary mining side is 3000mm. The row spacing of the two rows of hollow grouting anchor cables is 2200mm. The spacing between adjacent hollow grouting anchor cables 4 in the same row is 2200mm. The specifications of the hollow grouting anchor cables 4 are φ21.8mm and 9300mm in length.

[0048] Step 2: As the working face is mined, in an area of ​​no less than 20m ahead of the working face, i.e., the hollow grouting anchor cable grouting area 14, the roof of the roadway is reinforced by grouting using hollow grouting anchor cables 4; the grouting material is silicate modified polyurethane material for coal mine reinforcement, the grouting pressure is no less than 3MPa, the grout wraps the anchor cable and fills the cracks in the roof rock layer, forming a stable structure for the roof.

[0049] Step 3: During the roadway retention process, as the working face advances, a layer of flexible netting 16 needs to be laid in front of the 10th end support frame. The flexible netting 16 is laid in front of the 2nd end support frame towards the tail of the machine, with a width of not less than 10m. One side of the flexible netting extends 500mm into the roadway and is securely tied to the metal mesh on the roof of the roadway, while the other side extends naturally. The length of the flexible netting 16 is consistent with the advance of the working face.

[0050] Step 4: After the end support 10 frames and at the front end of the formwork device, lay another layer of No. 8 diamond-shaped metal mesh 11 below the original flexible mesh 16; one side of the No. 8 diamond-shaped metal mesh 11 extends 500mm beyond the goaf side of the flexible formwork concrete wall, and the other side extends into the roadway; the total width of the No. 8 diamond-shaped metal mesh 11 is 3000mm; the No. 8 diamond-shaped metal mesh 11 and the original roof protection mesh in the roadway are connected with No. 14 rust-proof iron wire through holes to ensure that the mesh is firmly connected.

[0051] Step 5: As the work surface advances, after the end support 10 frames and the front end of the formwork device, lay the No. 8 diamond-shaped metal mesh 11, and then drill anchor bolt holes at certain intervals. After installing the anchor bolts 6 in the anchor bolt holes, use the anchor bolt tray to support a high-strength steel plate. The anchor bolts 6 and the high-strength steel plate 9 form a rigid combined support structure 5, which together fixes the No. 8 diamond-shaped metal mesh 11, and also strengthens the top plate above the flexible formwork concrete wall 7, inhibiting the top rock layer from spreading along the flexible formwork. The top slab of concrete wall 7 underwent shear settlement deformation; the supplementary anchor rods 6 used in the rigid composite support structure 5 are left-hand threaded steel anchor rods, installed along both sides of the flexible formwork concrete wall, with a distance of 150mm from the flexible formwork concrete wall 7, a diameter of φ22mm, and a length of 2500mm; the high-strength steel plate 9 of the rigid composite support structure 5 has a strength of Q235, a length of 1800mm, a width of 300mm, and a thickness of 10mm; holes are drilled on both sides of the high-strength steel plate 9, with a diameter sufficient for anchor rod installation.

[0052] Step 6: Hang the flexible mold using the formwork hanging device. After the flexible mold is hung, start pouring concrete. Once the concrete strength meets the demolding requirements, the formwork hanging device is removed and moves forward with the workpiece.

[0053] Step 7: Repeat steps 1-6 until the entire working face is left open.

[0054] Example 6 The present invention provides a method for shear protection of weak composite roof slabs in flexible formwork tunnels, which is implemented according to the following steps: Step 1: In the retained roadway, to prevent the flexible concrete wall 7 from shearing the roof, in the area 80m ahead of the working face, i.e., the hollow grouting anchor cable installation area 13, hollow grouting anchor cable 4 holes are drilled perpendicular to the roof using an anchor cable drilling rig and installed. Two rows of hollow grouting anchor cable 4 holes are drilled along the longitudinal direction of the retained roadway. The distance between the first row of hollow grouting anchor cable 4 and the primary mining side 15 is 500mm, and the distance between the second row and the secondary mining side is 2600mm. The row spacing of the two rows of hollow grouting anchor cables is 1800mm, and the spacing between adjacent hollow grouting anchor cables 4 in the same row is 1800mm. The hollow grouting anchor cable 4 has a specification of φ21.8mm and a length of 9300mm.

[0055] Step 2: As the working face is mined, in an area of ​​no less than 20m ahead of the working face, i.e., the hollow grouting anchor cable grouting area 14, the roof of the roadway is reinforced by grouting using hollow grouting anchor cables 4; the grouting material is silicate modified polyurethane material for coal mine reinforcement, the grouting pressure is no less than 3MPa, the grout wraps the anchor cable and fills the cracks in the roof rock layer, forming a stable structure for the roof.

[0056] Step 3: During the roadway retention process, as the working face advances, a layer of flexible netting 16 needs to be laid in front of the 10th end support frame. The flexible netting 16 is laid in front of the 2nd end support frame towards the tail of the machine, with a width of not less than 10m. One side of the flexible netting extends 500mm into the roadway and is securely tied to the metal mesh on the roof of the roadway, while the other side extends naturally. The length of the flexible netting 16 is consistent with the advance of the working face.

[0057] Step 4: After the end support 10 frames and at the front end of the formwork device, lay another layer of No. 8 diamond-shaped metal mesh 11 below the original flexible mesh 16; one side of the No. 8 diamond-shaped metal mesh 11 extends 300mm beyond the goaf side of the flexible formwork concrete wall, and the other side extends into the roadway; the total width of the No. 8 diamond-shaped metal mesh 11 is 3000mm; the No. 8 diamond-shaped metal mesh 11 and the original roof protection mesh in the roadway are connected with No. 14 rust-proof iron wire through holes to ensure that the mesh is firmly connected.

[0058] Step 5: As the work surface advances, after the end support 10 frames and the front end of the formwork device, lay the No. 8 diamond-shaped metal mesh 11, and then drill anchor bolt holes at certain intervals. After installing the anchor bolts 6 in the anchor bolt holes, use the anchor bolt tray to support a high-strength steel plate. The anchor bolts 6 and the high-strength steel plate 9 form a rigid combined support structure 5, which together fixes the No. 8 diamond-shaped metal mesh 11, and also strengthens the top plate above the flexible formwork concrete wall 7, inhibiting the top rock layer from spreading along the flexible formwork. The top slab of concrete wall 7 underwent shear settlement deformation; the supplementary anchor rods 6 used in the rigid composite support structure 5 are left-hand threaded steel anchor rods, installed along both sides of the flexible formwork concrete wall, with a distance of 150mm from the flexible formwork concrete wall 7, a diameter of φ22mm, and a length of 2500mm; the high-strength steel plate 9 of the rigid composite support structure 5 has a strength of Q235, a length of 1800mm, a width of 300mm, and a thickness of 10mm; holes are drilled on both sides of the high-strength steel plate 9, with a diameter sufficient for anchor rod installation.

[0059] Step 6: Hang the flexible mold using the formwork hanging device. After the flexible mold is hung, start pouring concrete. Once the concrete strength meets the demolding requirements, the formwork hanging device is removed and moves forward with the workpiece.

[0060] Step 7: Repeat steps 1-6 until the entire working face is left open.

Claims

1. A flexible formwork-based shear-resistant support system for weak composite roof slabs in roadways with goaf entry, characterized in that: This includes an advanced working face grouting support structure, a flexible mesh laid in front of the end support frame, a diamond-shaped metal mesh added behind the end support frame, anchor rods and steel plates used to fix the diamond-shaped metal mesh, and additional anchor rods and steel plates to reinforce the top slab of the space to be poured.

2. The shear protection system for weak composite roof slabs along the goaf in accordance with claim 1, characterized in that, The advanced working face grouting support structure is constructed by using an anchor cable drilling rig to drive hollow grouting anchor cables perpendicular to the top plate within a range of no less than 80m from the advanced working face.

3. The shear protection system for weak composite roof slabs along the goaf in accordance with claim 2, characterized in that, The hollow grouting anchor cables are installed in two rows along the longitudinal direction of the roadway. The distance between the first row and the first backfill side is 600mm, and the distance between the second row and the first row is 2000mm. The spacing is 2000mm. The diameter of the hollow grouting anchor cable is 21.8mm and the length is 9300mm.

4. A flexible formwork-based shear-resistant support system for weak composite roof slabs in goaf-side entry tunnels, characterized in that: The advanced working face grouting support structure shall carry out grouting reinforcement of the top plate within a range of not less than 20m of the advanced working face.

5. The shear protection system for weak composite roof slabs along the goaf in accordance with claim 4, characterized in that, The material used for roof grouting is silicate-modified polyurethane material for reinforcing coal and rock in coal mines.

6. The shear protection system for weak composite roof slabs along the goaf in accordance with claim 5, characterized in that, One side of the diamond-shaped metal mesh extends 300-500mm beyond the goaf side of the flexible concrete wall, while the other side extends into the roadway.

7. The shear protection system for weak composite roof slabs along the goaf in accordance with claim 6, characterized in that, The anchor bolts used for the replacement are threaded steel anchor bolts, which are installed along both sides of the flexible concrete wall.

8. A method for shear protection of weak composite roof slabs in flexible formwork-assisted tunnels, characterized in that, include; Step 1: Drill grouting holes at the advanced working face and install hollow grouting anchor cables; Step 2: As the working face is mined, the roof of the roadway is reinforced by grouting using hollow grouting anchor cables; Step 3: As the working face advances, a flexible net is laid in front of the end support frame; Step 4: Lay a diamond-shaped metal mesh underneath the flexible mesh; Step 5: After laying the diamond-shaped metal mesh, drill additional anchor bolt holes, install additional anchor bolts in the additional anchor bolt holes, and support the steel plate with the anchor bolt tray; Step 6: After the formwork is installed by the formwork hanging device, concrete pouring begins. Afterward, the formwork hanging device is removed from the formwork and moves forward with the workpiece. Step 7: Repeat steps 1-6 until the entire working face is left open.

9. The method for shear protection of weak composite roof slabs along the goaf in accordance with claim 8, characterized in that, In step 1: In order to prevent the shearing effect of the flexible concrete wall on the roof in the roadway, hollow grouting anchors are installed in an area of ​​no less than 80m ahead of the working face, i.e., the area where hollow grouting anchors are installed. The hollow grouting anchors are installed in two rows along the longitudinal direction of the roadway. The distance between the first row of hollow grouting anchors and the primary mining side is 500-700mm. The distance between the second row and the secondary mining side is 2600-3000mm. The distance between the two rows of hollow grouting anchors is 1800-2200mm. The distance between adjacent hollow grouting anchors in the same row is 1800-2200mm.

10. The shear-resistant support system for weak composite roof slabs along the goaf in accordance with claim 9, characterized in that, In step 2: the grouting material is silicate-modified polyurethane material for coal mine reinforcement, the grouting pressure is not less than 3MPa, the grout wraps the anchor cable and fills the cracks in the roof rock layer, forming a stable structure in the roof.

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