Working face advanced reinforcement method based on large-diameter grouting anchor cable truss

Abstract

The invention relates to a working face advanced reinforcement method based on a large-diameter grouting anchor cable truss, which comprises the following steps of: after a roadway is excavated, carrying out anchor net cable support on the roadway by adopting an anchor rod and an anchor cable, ensuring the initial stability of the roadway through high pre-tightening and high surface protection, and carrying out secondary reinforcement construction by adopting a large-diameter grouting anchor cable lagging excavation surface to realize parallel construction of roadway excavation. While the tunneling speed is not influenced, the transverse and trend control performance of the support body on the roadway is improved, and the surrounding rock constraint effect is strengthened; the large-diameter grouting anchor cable is subjected to grouting reinforcement by adopting a high-strength paste anchoring material before mining of the working face, so that strong anchoring of the large-diameter grouting anchor cable and a surrounding rock body is ensured, high-strength bearing of advanced mining-induced stress of the working face is ensured, the large-diameter grouting anchor cable and the surrounding rock body are coupled with a fracture development rule of the surrounding rock, and the surrounding rock is reinforced and broken through slurry diffusion; no auxiliary passive support equipment is arranged in working face stoping, the roadway space is not occupied, and roadway ventilation and safe and orderly operation environment are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of mine tunnel support, and in particular to a working face advance reinforcement method based on a large-diameter grouting anchor cable truss. Background Art

[0002] With the increase in the depth and scale of coal mining, the geological conditions are becoming more complex. The coal mining face tunnels are supported by anchor mesh spraying or scaffolding, which are greatly affected by dynamic pressure. The tunnels deform quickly and with large deformation. Usually, single hydraulic pillars, advance hydraulic supports, single hydraulic pillars combined with articulated top beams are used in the advance section of the tunnel for secondary reinforcement. There are many disadvantages. First, the advance support distance is relatively short. Before the advance reinforcement, the surrounding rock has been damaged by the mining stress and the support timing is not timely. Second, the tunnel support lacks overall consideration. Most mining tunnels only consider supporting the roof. A large number of additional anchor cables further damage the integrity of the roof, causing the anchor rods / anchor cables to move outward with the surrounding rock, and the support effect cannot be exerted. The cross-sectional shrinkage rate can even reach more than 70%. Third, it occupies tunnel space, the operation process is complicated, the labor intensity is high, and the support speed is slow, resulting in the equipment in the tunnel being unable to move. The cross-section must be repeatedly expanded before it can be barely used, affecting the coal mining speed of the working face.

[0003] Anchor grouting support is one of the effective methods for support and reinforcement under complex and difficult conditions. Domestic mine tunnel support also applies hollow grouting anchor rods / anchor cables to tunnel support under deep, high-stress and complex geological conditions, and has achieved good support effects. However, for the advance reinforcement of mining tunnels, after adopting anchor grouting support, it is still shown that the support strength is insufficient and the surrounding rock cannot be strongly constrained. The slurry solidification strength and diffusion range are small, which is only equivalent to achieving full anchoring of the anchor cable. Secondly, the problem of insufficient support range leads to large deformation of the tunnel and has to be renovated, resulting in complicated construction procedures, high labor intensity of construction workers and low efficiency. Summary of the Invention

[0004] In order to overcome the shortcomings of existing technologies in advance reinforcement of mining tunnels, such as low support strength, small advance reinforcement distance, and serious occupation of tunnel space affecting ventilation, the present invention provides a working face advance reinforcement method based on large-diameter grouting anchor truss, which is suitable for the needs of advance support and reinforcement of coal mine mining tunnels, and combines the advantages of high-strength anchoring, full-length grouting, surrounding rock reinforcement, etc., and can effectively meet the mining tunnel support requirements under the influence of mining stress.

[0005] The present invention is achieved through the following technical solutions, providing a method for advanced reinforcement of a working surface based on a large-diameter grouting anchor cable truss, comprising the following steps: a. After the mining tunnel is excavated, anchor rods and anchor cables are used to support the mining tunnel with anchor nets; b. After completing the anchor net support, large diameter grouting anchor cables and anchor cable trusses are used to lag the excavation working face for secondary reinforcement support. During the secondary reinforcement support, large diameter grouting anchor cables are not grouted; c. Before mining at the coal mining face, grouting reinforcement is carried out on large diameter grouting anchor cables.

[0006] In this plan, anchor mesh support is first carried out in the mining tunnel. High pre-tightening and high protection surface are used to ensure the initial stability of the tunnel without affecting the tunnel excavation speed. Then, large-diameter grouting anchor cables are constructed after the excavation face to achieve parallel construction of the tunnel excavation and control the lateral and direction performance of the tunnel, strengthen the restraint effect of the surrounding rock, and use high-strength paste anchoring materials to grout and reinforce the large-diameter grouting anchor cables before the working face is mined. This ensures that the large-diameter grouting anchor cables are strongly anchored to the surrounding rock mass, and can bear high-strength stress caused by advanced mining. It is coupled with the development law of surrounding rock cracks to achieve slurry diffusion and reinforcement of broken surrounding rock.

[0007] As an optimization, a double-layer anchor mesh is used to protect the mining roadway surface during anchor cable support. Multiple rows of anchor rods are arranged side by side along the mining direction, connected by steel bands. Anchor cables are installed between adjacent rows of anchor rods in the mining roadway roof. This solution uses a double-layer anchor mesh to protect the mining roadway surface, preventing the fall of gravel from the roadway surface. Steel bands increase the surface protection area and strength, and anchor cables reinforce the support of the mining roadway roof to ensure roof stability.

[0008] As an optimization, secondary reinforcement support is carried out 30m after the excavation face of the delayed mining roadway. This is done a certain time after the anchor-net support is completed, without affecting normal excavation. It is also carried out after the anchor-net support structure stabilizes, which helps release stress in the surrounding rock.

[0009] As an optimization, during secondary reinforcement support, multiple steel belts are compressed by anchor trusses. Large-diameter grouting anchors are sequentially threaded through anchor locks, anchor trusses, and anchor trays, and secured to the roof and sides of the mining roadway with high preload. The anchor trusses in this solution compress the multiple steel belts, thereby ensuring overall structural stability of the support structure.

[0010] As an optimization, advance grouting reinforcement is carried out on large-diameter grouting anchor cables no less than 7 days before the mining face is mined. The advance grouting reinforcement distance is no less than the distance affected by the advance mining stress, and no less than 30m. According to the mining speed and distance of the coal mining face, the advance grouting reinforcement distance is maintained at no less than 50m, and the mining time from the coal mining face is no less than 7 days. In this plan, advance grouting reinforcement is carried out on large-diameter grouting anchor cables no less than 7 days before the mining face is mined. At this time, the tunnel has been excavated for a long time and has not been severely affected by mining stress. The degree of development of surrounding rock cracks is high. Grouting reinforcement is conducive to further strengthening the integrity of the surrounding rock and the connection between the support body and the surrounding rock anchor, improving the bearing capacity of the surrounding rock-support system, and ensuring the stability of the mining tunnel under the influence of advance mining stress.

[0011] As an optimization, during grouting reinforcement, the high-strength paste anchor slurry is in a viscous paste state, the slurry water-to-material ratio is not higher than 1:4, the 7-day curing strength is not less than 45MPa, the 28-day curing strength is not less than 70MPa, and the final hole pressure is not less than 7MPa.

[0012] As an optimization, the yield strength of the anchor rod is not less than 500 MPa, the diameter is not less than 22 mm, and the applied preload is not less than 50% of the yield load of the anchor rod.

[0013] As an optimization, the yield strength of the anchor cable is not less than 1860MPa, the diameter is not less than 22mm, the applied preload is not less than 40% of the anchor cable breaking load, the anchor end should reach the depth of the top plate stable layer, and the anchor cables are arranged in rows in the middle of the anchor rod row spacing.

[0014] As an optimization, the breaking strength of the large diameter grouting anchor cable is not less than 800KN, the diameter is not less than 32mm, and the applied preload is not less than 30% of the breaking load of the large diameter grouting anchor cable.

[0015] As an optimization, the anchor truss is made of U-shaped steel beams, I-beams or other special-shaped steel beam structures. The material yield strength is not less than 345MPa and the tensile strength is not less than 510MPa. The anchor truss is provided with multiple anchor truss through holes for large-diameter grouting anchors to pass through.

[0016] The beneficial effects of the present invention are: After the tunnel is excavated, anchor rods and anchor cables are used to support the tunnel with anchor mesh cables. High preload and high protection surface are used to ensure the initial stability of the tunnel, without affecting the tunnel excavation speed and meeting the mine production continuity requirements.

[0017] Large-diameter grouting anchor cables are constructed after the excavation face is constructed. Multiple large-diameter grouting anchor cables are connected along the direction of the tunnel through anchor cable trusses. At the same time, multiple steel belts are tightened to strengthen the surface protection, so as to achieve parallel construction of tunnel excavation and control performance of the tunnel in the horizontal direction and direction, and strengthen the restraint effect of surrounding rock.

[0018] Before mining the working face, high-strength paste anchoring materials are used to grout and reinforce large-diameter grouting anchor cables, ensuring strong anchoring of the large-diameter grouting anchor cables to the surrounding rock mass, bearing high-strength stress caused by advanced mining, and coupling with the development law of surrounding rock cracks to achieve slurry diffusion and reinforcement of broken surrounding rocks.

[0019] The working face has been reinforced in advance without installing auxiliary passive support equipment, which does not occupy the tunnel space and ensures that the tunnel ventilation and working environment are safe and orderly. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a cross-sectional view of the invention showing the implementation of anchor wire mesh support after the mining tunnel is excavated; Figure 2 This is a cross-sectional view of the secondary reinforcement support implemented in the present invention; Figure 3 A plan view of the roof for implementing secondary reinforcement support according to the present invention; Figure 4 This is a plan view of the side portion for implementing secondary reinforcement support according to the present invention; Figure 5 It is a schematic plan view of the coal mining working face of the present invention; Figure 6 This is a side view of the installation structure of the anchor cable truss and the large-diameter grouting anchor cable of the present invention; Figure 7 This is a cross-sectional view of the installation structure of the anchor cable truss and the large-diameter grouting anchor cable of the present invention; Figure 8 This is a cross-sectional view of the installation structure of another anchor truss and large-diameter grouting anchor cable of the present invention; As shown in the figure: 1. Anchor rod, 2. Anchor cable, 3. Large diameter grouting anchor cable, 31. Anchor cable lock, 32. Anchor cable tray, 4. Anchor cable truss, 41. Anchor cable truss through hole, 5. Steel belt, 6. Double-layer anchor net, 7. Coal mining working face, 71. Mining tunnel, 72. Distance affected by advanced mining stress, 73. Mining direction of working face, 74. Cutting eye of working face. DETAILED DESCRIPTION

[0021] In order to clearly illustrate the technical features of this solution, this solution is described below through specific implementation methods.

[0022] During the mining process, Figure 5 As shown, the mining tunnel 71 and the working face cut 74 connecting the two mining tunnels 71 are first excavated. The coal mining machine is set in the working face cut 74, and then mining is carried out along the working face mining direction 73 to mine the coal seam in the mining working face 7. Figure 5 The shaded part in the middle is the coal mining face 7.

[0023] like Figures 1 to 8As shown, the method for advanced reinforcement of a working surface based on a large-diameter grouting anchor truss of the present invention comprises the following steps: After the mining tunnel 71 is excavated to the designed cross-sectional dimensions, that is, after it has been excavated a certain distance and a cross-sectional area consisting of a side and a roof is formed, anchor rods 1 and anchor cables 2 are used to support the mining tunnel 71 with an anchor mesh.

[0024] When anchor mesh cable support is used, a double-layer anchor mesh 6 is first used to protect the surface of the mining tunnel 71. In this embodiment, a double-layer anchor mesh 6 composed of a 30×30mm grid plastic double-resistance mesh and a 100×100mm grid steel mesh is used to provide high-density and high-strength protection for the surface of the mining tunnel 71.

[0025] A plurality of steel belts 5 are arranged along the excavation direction of the mining tunnel 71. The steel belts 5 are vertically arranged on the side of the mining tunnel 71 and extend left and right on the top plate of the mining tunnel 71. The steel belts on the side of the mining tunnel 71 and the steel belts on the top plate of the mining tunnel 71 can be connected or separately arranged, and are generally separately arranged.

[0026] Anchor rods 1 in a row are connected together by steel bands 5, enhancing the support structure's restraint area and strength on the surrounding rock. The anchor rods 1 have a yield strength of no less than 500 MPa, a diameter of no less than 22 mm, and an applied preload of no less than 50% of the yield load of the anchor rods 1. The anchor rods 1 in this embodiment are MSGLD-500 / 22, with a preload of 100 kN and a length exceeding the base top depth, which in this embodiment is 2500 mm.

[0027] like Figure 3 As shown, the anchor cable 2 is installed on the roof of the mining tunnel 71 between adjacent steel belts 5, and the anchor cables 2 are arranged in rows in the middle of the anchor rod 1 row spacing. The yield strength of the anchor cable 2 is not less than 1860MPa, the diameter is not less than 22mm, the applied preload is not less than 40% of the breaking load of the anchor cable 2, and the anchoring end should reach the depth of the roof stable layer. In this embodiment, the specification model of the anchor cable 2 is SKP22-1 / 1860, the preload is 240KN, and the length exceeds the roof stable rock layer by 1m. In this embodiment, 7300mm is selected.

[0028] After 30m of the excavation face of delayed mining tunnel 71 and after completing the anchor mesh support, large-diameter grouting anchor cables 3 and anchor cable trusses 4 are used to perform secondary reinforcement support on the delayed excavation working face. During the secondary reinforcement support, the large-diameter grouting anchor cables 3 are not grouted.

[0029] During secondary reinforcement support, multiple large diameter grouting anchor cables 3 are connected through the anchor cable truss 4, and multiple steel belts 5 are compressed. Figure 3 、 4 As shown, the anchor cable truss 4 is perpendicular to the steel belt 5 . In this embodiment, the length direction of the anchor cable truss 4 is consistent with the excavation direction of the mining tunnel 71 .

[0030] The anchor truss 4 is made of U-shaped steel beams, I-shaped steel beams or other special-shaped steel beam structures. The material yield strength is not less than 345 MPa and the tensile strength is not less than 510 MPa. The anchor truss 4 is provided with multiple anchor truss through holes 41 for large-diameter grouting anchor cables 3 to pass through.

[0031] The anchor truss 4 is connected to multiple large-diameter grouting anchors 3 along the direction of the mining tunnel 71. The large-diameter grouting anchors 3 pass through the anchor locks 31, the anchor truss through holes 41 and the anchor trays 32 in sequence, and are fixed to the roof and side of the mining tunnel 71 with high preload force.

[0032] The large-diameter grouting anchor cable 3 has a breaking strength of no less than 800 kN, a diameter of no less than 32 mm, and an applied preload of no less than 30% of the breaking load of the large-diameter grouting anchor cable 3. In this embodiment, the large-diameter grouting anchor cable 3 has a specification of SKZ32-1 / 1770-8300 mm and a preload of 300 kN. It is located midway between the rows of anchor cables 2. During installation, the large-diameter grouting anchor cable 3 is anchored with a resin anchoring agent, and the cable body is inserted into a 300×300×20 mm anchor tray 32. The anchor truss 4 is then connected to multiple large-diameter grouting anchor cables 3 through the anchor truss through-holes 41 along the direction of the mining roadway 71. Finally, an anchor lock 31 is installed at the tail end of the cable body for tensioning and preload.

[0033] Before mining the coal face 7, the large-diameter grouting anchor cable 3 is reinforced by grouting. Specifically, at least 7 days before mining the coal face 7, the large-diameter grouting anchor cable 3 is reinforced by advance grouting. The advance grouting reinforcement distance is not less than the advance mining stress influence distance 72 (in this embodiment, more than 50 meters) and not less than 30 meters. The advance mining stress influence distance 72 refers to the stress influence distance in front of the mining roadway 71 during mining. Beyond this distance, the destructive effect of the advance mining stress on the mining roadway 71 is small. Within this distance, the advance mining stress has a more obvious effect on the stability of the mining roadway 71. Therefore, grouting reinforcement is required within the advance mining stress influence distance 72.

[0034] Based on the mining speed and distance of the coal mining face 7, the advance grouting reinforcement distance is maintained at no less than 50m, and the mining time from the coal mining face 7 is no less than 7 days. In other words, when mining reaches a certain position, the area 50 meters in front of that position has been grouting at least 7 days in advance. At this time, the tunnel has been excavated for a long time and has not been severely affected by mining stress. The surrounding rock has a high degree of crack development. Grouting reinforcement can further strengthen the integrity of the surrounding rock and the connection between the support and surrounding rock anchorage, improve the bearing capacity of the surrounding rock-support system, and ensure the stability of the mining roadway under the influence of advanced mining stress.

[0035] During grouting reinforcement, the high-strength paste anchor slurry has a water-to-cement ratio of no higher than 1:4, a seven-day curing strength of no less than 45 MPa, a 28-day curing strength of no less than 70 MPa, and a final hole pressure of no less than 7 MPa. The high-strength paste anchor slurry is viscous and paste-like, leveraging its high adhesion, high curing strength, and high thixotropy to strongly anchor the large-diameter grouting anchor cable 3 to the broken surrounding rock mass. The slurry then penetrates and diffuses into the free borehole section of the anchor rod 1 and anchor cable 2 supported by the anchor mesh cable, strengthening the bearing capacity of the anchor rod 1 and anchor cable 2 to the surrounding rock, and enhancing the overall bearing capacity of the support and surrounding rock mass.

[0036] The present invention combines the anchor mesh cable support of the mining tunnel with the high-strength anchor grouting secondary support. On the basis of the anchor mesh cable support with high preload and strong protection, large-diameter grouting anchor cables and high-strength paste anchoring materials are used to implement enhanced support in stages, which not only improves the tunnel support strength and rigidity before the tunnel is affected by mining stress, but also implements grouting reinforcement during the development period of surrounding rock cracks in the mining tunnel during the mining of the working face, realizes secondary grouting enhancement and modification of the surrounding rock, improves the integrity and bearing capacity of the surrounding rock-support system, and meets the requirements of the stability of the mining tunnel for the advance mining stress. In addition, the present invention eliminates the human and material resources required for advance reinforcement, has high support initiative, does not occupy tunnel space, meets the needs of tunnel ventilation, transportation, etc., and solves the problem of advance support of mining tunnels under high-stress, complex and difficult conditions in China.

[0037] Of course, the above description is not limited to the above examples. Technical features not described in the present invention can be achieved by or by adopting existing technologies, which will not be described here. The above embodiments and drawings are only used to illustrate the technical solutions of the present invention and are not limitations of the present invention. The present invention is described in detail with reference to the preferred implementation methods. Ordinary technicians in this field should understand that changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention do not depart from the purpose of the present invention and should also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for advanced reinforcement of working surface based on large diameter grouting anchor truss, characterized in that: The steps include: a. After the mining tunnel (71) is excavated, anchor rods (1) and anchor cables (2) are used to support the mining tunnel (71) with anchor net cables; b. After the anchor net cable support is completed, the large diameter grouting anchor cable (3) and the anchor cable truss (4) are used to lag the excavation working face for secondary reinforcement support. During the secondary reinforcement support, the large diameter grouting anchor cable (3) is not grouted; c. Before mining the coal working face (7), the large diameter grouting anchor cable (3) is reinforced by grouting.

2. The method for advanced reinforcement of a working surface based on a large-diameter grouting anchor truss according to claim 1 is characterized in that: During anchor net cable support, a double-layer anchor net (6) is used to protect the mining roadway (71), multiple rows of anchor rods (1) are arranged side by side along the excavation direction of the mining roadway (71), and the anchor rods (1) in the same row are connected together using a steel belt (5), and the anchor cable (2) is installed in the middle of the row spacing of adjacent anchor rods (1) on the top plate of the mining roadway (71).

3. The method for advanced reinforcement of a working surface based on a large-diameter grouting anchor truss according to claim 1 is characterized in that: Secondary reinforcement support was carried out 30m after the excavation face of the delayed mining tunnel (71).

4. The method for advanced reinforcement of a working surface based on a large-diameter grouting anchor truss according to claim 1 is characterized in that: During secondary reinforcement support, multiple steel belts (5) are compressed by the anchor truss (4), and the large-diameter grouting anchor (3) passes through the anchor lock (31), the anchor truss (4) and the anchor tray (32) in sequence, and is fixed to the top plate and the side of the mining tunnel (71) with a high preload force.

5. The method for advanced reinforcement of a working surface based on a large-diameter grouting anchor truss according to claim 1 is characterized in that: At least 7 days before the mining face (7) is mined, the large diameter grouting anchor cable (3) is subjected to advance grouting reinforcement. The advance grouting reinforcement distance is not less than the advance mining stress influence distance (72) and is not less than 30m. According to the mining speed and distance of the mining face (7), the advance grouting reinforcement distance is maintained at not less than 50m, and the mining time from the mining face (7) is not less than 7 days.

6. The method for advanced reinforcement of a working surface based on a large-diameter grouting anchor truss according to claim 1 is characterized in that: During grouting reinforcement, the high-strength paste anchor slurry is in a viscous paste state, the slurry water-to-material ratio is not higher than 1:4, the 7-day curing strength is not less than 45MPa, the 28-day curing strength is not less than 70MPa, and the final hole pressure is not less than 7MPa.

7. The method for advanced reinforcement of a working surface based on a large-diameter grouting anchor truss according to claim 1 is characterized in that: The yield strength of the anchor rod (1) is not less than 500 MPa, the diameter is not less than 22 mm, and the applied preload is not less than 50% of the yield load of the anchor rod (1).

8. The method for advanced reinforcement of a working surface based on a large-diameter grouting anchor truss according to claim 1 is characterized in that: The yield strength of the anchor cable (2) is not less than 1860 MPa, the diameter is not less than 22 mm, the applied preload is not less than 40% of the breaking load of the anchor cable (2), the anchor end should reach the top plate stable layer depth, and the anchor cables (2) are arranged in rows in the middle of the anchor rod (1) row spacing.

9. The method for advanced reinforcement of a working surface based on a large-diameter grouting anchor truss according to claim 1 is characterized in that: The breaking strength of the large-diameter grouting anchor cable (3) is not less than 800KN, the diameter is not less than 32mm, and the applied preload is not less than 30% of the breaking load of the large-diameter grouting anchor cable (3).

10. The method for advanced reinforcement of a working surface based on a large-diameter grouting anchor truss according to claim 1 is characterized in that: The anchor truss (4) is made of a U-shaped steel beam, an I-shaped steel beam or other special-shaped steel beam structure, the material yield strength is not less than 345 MPa, and the tensile strength is not less than 510 MPa. The anchor truss (4) is provided with a plurality of anchor truss through holes (41) for large-diameter grouting anchor cables (3) to pass through.

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