A coal roadway rock burst prevention and control method combining energy absorption grouting and large-diameter pressure relief hole

Abstract

The application discloses a coal roadway rock burst prevention and treatment method combining energy absorption grouting and large-diameter pressure relief holes, and relates to the field of deep coal mine dynamic disaster prevention and control. While reducing the stress peak value and high stress range of the roadway surrounding rock, the coal body is reinforced to prevent the large-diameter pressure relief hole from excessively relieving pressure on the two sides of the coal seam roadway. In addition, the large deformation of the large-diameter pressure relief hole and the energy absorption grouting material provides a larger compensation space for the deformation and energy release of the coal body, thereby reducing the threat of impact mine pressure and other dynamic disasters in deep coal mining. The method comprises the following steps: S1, drilling a hydraulic fracturing pilot hole; S2, hydraulic fracturing; S3, grouting reinforcement in the fracturing area; and S4, drilling a large-diameter pressure relief hole. The construction sequence of 'pressure relief-reinforcement-pressure relief' avoids the problems of excessive pressure relief and damage to the integrity of the support structure caused by directly drilling a large-diameter pressure relief hole in a broken coal seam, and reduces the risk of impact mine pressure from two directions of pressure relief and reinforcement.

Description

Technical Field

[0001] The present invention relates to the field of deep coal mine dynamic disaster prevention and control, and in particular to a coal mine impact pressure prevention and control method combining energy-absorbing grouting with large-diameter pressure relief holes, which is suitable for decompression and crisis relief of deep high-stress tunnels and reinforcement of weak coal seam tunnels. Background Art

[0002] On the one hand, as my country's coal mining depths increase, high-stress roadways increase, surrounding rock stress continues to increase, and surrounding rock deformation and instability become increasingly common, leading to frequent sudden dynamic disasters such as rock bursts. On the other hand, approximately 40% of my country's coal mine working faces are located in weak coal seams. Disturbed coal seams are highly fragmented, making support difficult. Conventional support systems are also difficult to effectively control, posing a significant threat to the safety of workers, production efficiency, and machinery. These challenges present a pressing technical challenge for deep coal mining in my country.

[0003] Large-diameter drilling pressure relief is a commonly used pressure relief method for high-stress tunnels and impact mine pressure tunnels, and is widely used in the field of underground engineering. The essence of large-diameter drilling pressure relief is to absorb the elastic energy accumulated in the surrounding rock by utilizing the deformation and damage of the borehole under high stress conditions, thereby reducing the high stress value around the tunnel and reducing the high stress area, so that the stress concentration area is transferred to the deep part of the surrounding rock, which plays a protective role for the tunnel. However, for softer coal rock formations, large-diameter pressure relief holes often have excessive pressure relief and will destroy the stability of the coal tunnel support structure. Chinese patent CN202010439413 discloses a coal seam deep hole blasting pressure relief method that uses the original pressure relief hole to improve the blasting effect. It reduces the number of large-diameter boreholes drilled and performs deep hole blasting in the original large-diameter borehole to improve the pressure relief effect. However, the process of deep hole blasting is complicated and the effect is not easy to control, which will increase the difficulty and cost of support in the later stage. In order to overcome the shortcomings of large-diameter pressure relief holes in the application of coal seam pressure relief, the grouting reinforcement technology of soft and broken coal roadways and the local filling and strengthening technology of large-diameter drilling pressure relief anchoring layers have emerged, which have improved the strength of weak coal seams to a certain extent. However, due to the limitations of construction technology, although the above methods have improved the strength of the coal body, the original pressure relief effect has been significantly reduced. In addition, the existing large-diameter pressure relief methods play a single role and often only play a pressure relief role. They are easily restricted by the properties of the coal and rock mass during drilling. Therefore, it is urgent to invent a method for preventing and controlling rock burst that can not only significantly relieve pressure but also reinforce the coal body and ensure the stability of the coal roadway support structure, so as to meet the pressure relief needs of deep high-stress tunnels and rock burst tunnels and respond to the occurrence of deep dynamic disasters. Summary of the Invention

[0004] To address these issues, the present invention proposes a method for preventing and controlling rock bursts in coal seams by combining energy-absorbing grouting with large-diameter pressure-relieving holes. This method reduces peak stress and high-stress ranges in the surrounding rock of the roadway while reinforcing the coal mass, preventing excessive pressure relief from the large-diameter pressure-relieving holes on either side of the coal seam roadway. Furthermore, the large-diameter pressure-relieving holes and the large deformation of the energy-absorbing grouting material provide greater compensation space for the energy released by coal deformation, reducing the threat posed by dynamic hazards such as rock bursts during deep coal mining.

[0005] The technical solution of the present invention is: comprising the following steps:

[0006] S1. Drilling hydraulic fracturing pilot holes: Drilling hydraulic fracturing pilot holes obliquely upward in the side of the tunnel;

[0007] S2. Hydraulic fracturing: Multiple fracturing zones are evenly arranged in the hydraulic fracturing guide hole. Each fracturing zone is pre-cut using high pressure, and then fracturing is performed using low pressure.

[0008] S3, grouting reinforcement of the fracturing area: grouting is performed to fill the cracks formed in step S2;

[0009] S4. Drilling a large-diameter pressure relief hole: Expand the hydraulic fracturing guide hole to form a large-diameter pressure relief hole.

[0010] Furthermore, in step S1, a hydraulic fracturing pilot hole is drilled using a drilling rig, which has a diameter of 100 mm, a depth of 40 m, and an upward inclination of 5° from the horizontal;

[0011] A row of hydraulic fracturing guide holes is arranged on each side of the tunnel. The hydraulic fracturing guide holes are located in the middle of the tunnel, that is, the middle position of the two sides of the tunnel in the height direction. The center of the hydraulic fracturing guide hole is 1700mm away from the top plate, and the distance between the center of the openings of adjacent left and right hydraulic fracturing guide holes is 1500mm.

[0012] Furthermore, step S2 is specifically as follows: a fracturing zone is arranged every 3m in the hydraulic fracturing guide hole, and both sides of the fracturing zone are sealed with a packer. After the sealing is completed, a high-pressure water pump is used to pre-cut the seams, and the pressure value is not less than 60MPa; after the pre-cutting is completed, the pressure value is reduced to 30MPa to allow the cracks to continue to extend forward, the coal seam is broken and countless small cracks are formed. The cracks between the hydraulic fracturing holes are interconnected to form a pressure relief zone.

[0013] Furthermore, step S3 is specifically as follows: using the hydraulic fracturing guide hole as a filling path, using a grouting pump to fill the cracks generated by the hydraulic fracturing, and the filling material is asphalt or rubber grouting slurry.

[0014] Furthermore, step S4 specifically includes: based on the hydraulic fracturing pilot hole drilled in S1, further using a drilling rig to expand the hole diameter to 150 mm, and the drilling direction and layout spacing are consistent with the hydraulic fracturing pilot hole in S1.

[0015] Furthermore, the sides and roof of the tunnel are supported by anchor rods, the spacing between anchor rods is 800mm, and the spacing between anchor cables at the top of the tunnel is 1600mm.

[0016] The above technical solution of the present invention works as follows:

[0017] Before the surrounding rock deforms, a hydraulic fracturing pilot hole is drilled to form a pressure relief zone at the end of the hole, reducing the stress peak and high stress range of the tunnel surrounding rock, and transferring the stress concentration area from the two sides of the tunnel to the deep coal body, completing the initial pressure relief process.

[0018] When the high stress in the coal body is transferred from the two sides of the tunnel to the deep part of the coal body and the coal body structure is stable, hydraulic fracturing causes the cracks between the guide holes to expand and extend and penetrate each other, further releasing the stress of the surrounding rock, strengthening the initial pressure relief, and playing a role in pre-control of the impact mine pressure.

[0019] After the initial pressure relief is completed, asphalt or rubber grouting slurry is pumped in through a grouting pump to fill and reinforce the cracks and broken coal bodies induced by hydraulic fracturing, thereby improving the integrity and deformation energy absorption capacity of the broken coal bodies, avoiding excessive fragmentation of the pressure relief area, and reducing the difficulty of subsequent tunnel support. At the same time, the asphalt or rubber grouting slurry itself has the function of deformation energy absorption.

[0020] When the coal body deforms under load, the large-diameter pressure relief hole uses its own large deformation to provide a larger compensation space for the coal body deformation.

[0021] The beneficial effects of the above technical solution of the present invention are as follows:

[0022] The present invention has the dual impact mine pressure prevention and control functions of deformation energy absorption by large-diameter pressure relief holes and secondary energy absorption by grouting reinforcement of coal body energy-absorbing slurry. It not only changes the high stress state of the surrounding rock stress field by using the pressure relief holes, reduces the high stress value, reduces the stress range, and transfers the stress concentration area to the deep part of the surrounding rock, but also improves the integrity and deformation energy absorption capacity of the broken coal body by grouting the coal body with energy-absorbing slurry. In addition, the hydraulic fracturing guide hole is expanded to become a large-diameter pressure relief hole, which can be used for multiple purposes while also reducing the difficulty of drilling the pressure relief hole. The construction sequence of "pressure relief-reinforcement-pressure relief" avoids the problems of excessive pressure relief and damage to the integrity of the support structure caused by directly drilling large-diameter pressure relief holes in the broken coal seam, and reduces the risk of impact mine pressure from both the pressure relief and reinforcement directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of drilling a hydraulic fracturing pilot hole in an embodiment of the present invention;

[0024] FIG2( a ) is a schematic diagram of hydraulic fracturing operation according to an embodiment of the present invention;

[0025] FIG2( b ) is a schematic diagram of the hydraulic fracturing effect in an embodiment of the present invention;

[0026] Figure 3 Schematic diagram of the energy-absorbing grouting material filling process in an embodiment of the present invention;

[0027] Figure 4 Layout diagram of hydraulic fracturing pilot holes and large-diameter pressure relief holes in an embodiment of the present invention;

[0028] In the figure: 1-drilling rig, 2-transport vehicle, 3-drill bit, 4-hydraulic fracturing pilot hole, 5-coal seam, 6-fracturing zone, 7-packer, 8-hose, 9-flow meter and pressure control system, 10-pressure pump, 11-data recording system, 12-hydraulic fracturing-induced fissure, 13-pressure relief zone, 14-anchor rod, 15-anchor cable, 16-inflatable grouting plug, 17 grouting pump, 18-large-diameter pressure relief hole. DETAILED DESCRIPTION

[0029] In order to clearly illustrate the technical features of this patent, this patent is described in detail below through specific implementation methods and in combination with its accompanying drawings.

[0030] The present invention Figure 1-4 As shown, the implementation steps include the following:

[0031] S1. Drilling a hydraulic fracturing pilot hole; S2. Hydraulic fracturing; S3. Grouting reinforcement of the fracturing area; S4. Drilling a large-diameter pressure relief hole.

[0032] First, perform S1, drill the hydraulic fracturing pilot hole, such as Figure 1 As shown, a hydraulic fracturing pilot hole 4 with a diameter of 100 mm is drilled on a coal seam 5 using a drilling rig 1 with a drill bit 3. Figure 4 As shown, a row of holes is drilled on each side of the tunnel, located in the middle of the tunnel, that is, the middle position of the two sides of the tunnel in the height direction, 1700mm away from the roof, the left and right spacing of the guide holes is 1500mm, the hole depth is 40m, and the guide holes are tilted upward by 5° to facilitate the cleaning of coal dust in the hole. A pressure relief zone 13 is formed at the end of the hole through the drilled hydraulic fracturing guide hole 4, which reduces the high stress value and range of the tunnel surrounding rock, transfers the stress concentration area from the two sides of the tunnel to the deep coal seam, completes the initial pressure relief process, and provides a path for subsequent hydraulic fracturing and drilling of large-diameter pressure relief holes, playing a multi-purpose role of one hole, and at the same time reduces the difficulty of drilling pressure relief holes. The drilled coal dust is carried by a transport vehicle 2 connected to the drilling rig 1, avoiding subsequent cleaning work.

[0033] After the stress of the tunnel surrounding rock is transferred from the two sides of the tunnel to the deep coal body and the coal body structure is stable, S2, hydraulic fracturing, is carried out. As shown in Figure 2(a), before the start of hydraulic fracturing, a fracturing area 6 is arranged every 3m. The two sides of the fracturing area 6 are sealed with packers 7. After the sealing is completed, a pre-cutting is first performed using an ultra-high pressure water pump 10 with a pressure value of not less than 60MPa to shorten the total fracturing time. After the pre-cutting is completed, the pressure value is reduced to 30MPa so that the fracturing fluid can induce the fracture extension at a gentle speed to prevent excessive local pressure from causing the coal rock to collapse.

[0034] During the above process, in order to make a preliminary opening in the rock mass, a pressure of not less than 60 MPa was used in this case to quickly perform pre-fracture, which was shorter than the time required for subsequent 30 MPa fracturing. Afterwards, the pressure was reduced to 30 MPa. Due to the certain differences in the strength of the coal mass at different locations in the hole, the fracturing time was mainly determined by the data recording system, flow meter, and pressure control system, combined with the construction experience of the on-site construction personnel. The cracks continued to extend forward, causing the coal seam to break and form countless small hydraulic fracturing-induced cracks 12. The cracks between the hydraulic fracturing guide holes 4 were interconnected. The fracturing effect is shown in Figure 2(b). It should be explained that the cracks between the hydraulic fracturing guide holes 4 are interconnected, which means that the guide holes form a mutually interconnected pressure relief zone at the end. Figure 2(b) only shows a plan view of a pressure relief guide hole, which does not mean that the hydraulic fracturing-induced cracks 12 on a certain guide hole are interconnected with the pressure relief zone 13. This further releases the high stress of the coal mass, strengthens the initial pressure relief, and plays a role in pre-control of the rock burst.

[0035] After the hydraulic fracturing is completed, S3 and grouting reinforcement of the fracturing area are carried out, such as Figure 3 As shown, the hydraulic fracturing guide hole 4 is used as a filling path for energy-absorbing material filling and reinforcement. The grouting pipe is sent to the deepest fracturing area 6 through the hydraulic fracturing guide hole 4, and the fracturing area 6 is sealed on both sides with an inflatable grouting plug 16. After the sealing is completed, the hydraulic fracturing induced cracks 12 in the fracturing area 6 are filled and reinforced using a grouting pump 17. The filling material is asphalt or rubber grouting slurry, and the pumping pressure is not less than 40 MPa, so that the asphalt or rubber grouting slurry can fully flow in the hydraulic fracturing induced cracks 12 and finally solidify. After this step is completed, the next fracturing area 6 is filled from deep to shallow until all the hydraulic fracturing induced cracks 12 in all fracturing areas 6 are filled, so as to improve the strength and integrity of the coal body, avoid excessive fragmentation of the hydraulic fracturing induced cracks 12, and reduce the difficulty of later tunnel support. At the same time, the asphalt or rubber grouting slurry itself has the function of deformation and energy absorption.

[0036] Specifically, the rock burst mainly comes from the upper part of the roadway. Before the surrounding rock is deformed, the high stress around the roadway is transferred in the pressure relief zone 13. If grouting reinforcement is performed, the cost is too high and there is no obvious pressure relief effect. When rock burst occurs, the deformation energy absorption and pressure resistance mainly rely on the large-diameter pressure relief holes and the grouting materials. Therefore, the coal body strength and integrity mentioned in this article mainly refer to the integrity between the large-diameter pressure relief holes and the hydraulic fracturing-induced cracks.

[0037] During the fracturing process, the water outlet is connected to the flow meter and pressure control system 9 with a hose 8 to facilitate the control of the water outlet pressure. The flow meter and pressure control system 9 are then connected to the pressure pump 10 and the data recording system 11 in turn.

[0038] When Figure 3 After grouting and reinforcement of the fracturing zone is completed, the coal structure in the fractured zone stabilizes. Based on the hydraulic fracturing pilot hole 4 drilled in step S1, the diameter of the hole is further expanded to 150 mm using the drilling rig 1. The drilling direction and row spacing are consistent with S1. This avoids the instability caused by excessive pressure relief or insufficient coal strength when directly drilling large-diameter pressure relief holes, thereby ensuring the stability of the coal roadway support structure. When the surrounding rock deforms, the large-diameter pressure relief holes utilize their own large deformation to provide greater compensation space for the surrounding rock deformation, thus preventing the occurrence of rock burst.

[0039] like Figure 4 As shown, the hydraulic fracturing guide holes are located in the same position as the large-diameter pressure relief holes 18, and are arranged in one row on each side with a spacing of 1500mm. At the same time, the side of the tunnel is supported by anchor rods 14 with a spacing of 800mm between rows. The tunnel roof is supported by anchor rods 14 and anchor cables 15 arranged at a staggered spacing of 800mm. The spacing of the anchor rods along the width of the tunnel is 800mm, and the spacing of the anchor cables along the width of the tunnel is 1600mm.

[0040] There are many specific implementation ways of the present invention. The above is only the preferred implementation method of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principles of the present invention. These improvements should also be considered as the scope of protection of the present invention.

Claims

1. A method for preventing and controlling coal roadway rock burst pressure by combining energy-absorbing grouting with large-diameter pressure relief holes, characterized in that: The steps include: S1. Drilling hydraulic fracturing pilot holes: Drilling hydraulic fracturing pilot holes obliquely upward in the side of the tunnel; S2. Hydraulic fracturing: Multiple fracturing zones are evenly arranged in the hydraulic fracturing guide hole. Each fracturing zone is pre-cut using high pressure, and then fracturing is performed using low pressure. S3, grouting reinforcement of the fracturing area: grouting is performed to fill the cracks formed in step S2; S4. Drilling a large-diameter pressure relief hole: expanding the hydraulic fracturing pilot hole to form a large-diameter pressure relief hole; In step S1, a hydraulic fracturing pilot hole is drilled using a drilling rig, with a diameter of 100 mm, a depth of 40 m, and an upward inclination of 5° from the horizontal; A hydraulic fracturing pilot hole is arranged on each side of the roadway. The hydraulic fracturing pilot hole is located in the middle of the roadway. The center of the hydraulic fracturing pilot hole is 1700mm away from the roof, and the distance between the center of the hydraulic fracturing pilot hole on the left and right is 1500mm. Step S2 specifically includes: arranging a fracturing zone every 3 meters in the hydraulic fracturing pilot hole, sealing both sides of the fracturing zone with packers, and then pre-cutting the seams with a high-pressure water pump at a pressure of no less than 60 MPa. After the pre-cutting is completed, the pressure is reduced to 30 MPa to allow the fractures to continue to extend forward, rupturing the coal seam and forming numerous fine cracks. The cracks between the hydraulic fracturing holes are interconnected to form a pressure relief zone. Step S3 specifically includes: using the hydraulic fracturing pilot hole as a filling path, and using a grouting pump to fill the cracks generated by the hydraulic fracturing, with the filling material being asphalt or rubber grouting slurry; Step S4 specifically includes: based on the hydraulic fracturing pilot hole drilled in S1, further using a drilling rig to expand the hole diameter to 150 mm, and the drilling direction and layout spacing are consistent with the hydraulic fracturing pilot hole in S1.

2. The method for preventing and controlling coal roadway rock burst pressure by combining energy-absorbing grouting with large-diameter pressure relief holes according to claim 1, characterized in that: The sides and roof of the tunnel are supported by anchor rods, with an anchor rod spacing of 800mm and an anchor cable spacing of 1600mm at the top of the tunnel.

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