A method for determining the spacing between pressure relief holes and anchor holes based on unloading-support coordination

Abstract

The present invention discloses a method for determining the spacing between pressure relief holes and anchor holes based on the coordination of pressure relief and support, which belongs to the technical field of rock burst disaster prevention and control. The method comprises the following steps: Step A. Designing the optimal pressure relief hole-anchor hole spacing according to the pressure relief hole-anchor hole diameter ratio. First, it is necessary to calculate the crushing zone and plastic zone range R around the pressure relief hole-anchor hole. d 、R p 、r d 、r p In the present invention, by using numerical simulation software, the stress concentration coefficient between adjacent pressure relief holes and anchor holes and the amount of coal body movement on the roadway are calculated to determine whether the hole spacing has a synergistic effect. There is no need for on-site measured data, which saves corresponding testing time. Theoretical calculations can guide the hole spacing design during on-site production, which has reference value in the field of technical methods for preventing and controlling rock bursts. The crushing zone and plastic zone range around the pressure relief holes and anchor holes are calculated, as well as the range of the anchor support reinforcement zone.

Description

Technical Field

[0001] The present invention belongs to the technical field of rock burst disaster prevention and control, and in particular relates to a method for determining the spacing between a pressure relief hole and an anchor hole based on unloading-supporting coordination. Background Art

[0002] As the mining depth of coal mines in my country increases year by year, the complex conditions such as high ground stress and high mining disturbance faced by deep mining have led to frequent rock burst accidents, which seriously restricted the safe and efficient mining of coal mines in my country. Large-diameter drilling unloading and anchoring anti-bumping support are important means to prevent and control rock burst in tunnels. Large-diameter drilling unloading and anchoring anti-bumping support can form a dual-effect effect of unloading-support synergistic anti-bumping, and are widely used in the field of rock burst prevention and control. Therefore, a reasonable spacing between unloading holes and anchoring holes can effectively maintain the integrity of the tunnel, control surrounding rock deformation, and prevent the occurrence of rock burst.

[0003] Currently, the spacing between anchor bolts is set to a fixed value within a certain range based on calculations and national standards, while the spacing between pressure relief holes is fixed based on the different impact hazards of the roadway and working face. Little consideration has been given to the coordinated spacing between anchor holes and pressure relief holes. Roadway rock burst prevention and control generally focuses on two aspects: first, pressure relief and energy release. This involves implementing measures such as pressure relief holes to shift high-energy accumulation areas in the shallow part of the roadway surrounding rock deeper, forming a buffer energy-absorbing zone within the shallow area of ​​the roadway surrounding rock. Second, support is implemented. This involves reinforcing the shallow area of ​​the roadway surrounding rock through the implementation of anchor support and other technologies, forming a strong dynamic effect barrier within the shallow area of ​​the roadway surrounding rock. However, when the spacing between pressure relief holes and anchor holes is too small, the plastic zone around the pressure relief holes expands, causing the coal around the anchor holes to fracture, reducing the bearing capacity of the anchor support, and even causing anchor support failure. Therefore, it is particularly important to determine the optimal pressure relief hole-anchor hole spacing to minimize damage to the anchor support structure while ensuring sufficient coal pressure relief.

[0004] As for the synergistic effect of the spacing between the pressure relief holes and the anchor holes, under the condition of determining the diameters of the two holes, it is often the case that the hole spacing is too small, resulting in a decrease in the bearing capacity of the anchor support and severe deformation of the roadway side, and the hole spacing is too large, resulting in a high peak stress between the holes. Excessive elastic deformation of the coal accumulation can cause deformation of the roadway side. Therefore, a method for determining the spacing between the pressure relief holes and the anchor holes based on the synergy of the pressure relief holes and the anchor support is urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that, for the synergistic effect of the spacing between pressure relief holes and anchor holes, when determining the diameters of the two holes, the small hole spacing often leads to a decrease in the bearing capacity of the anchor support, causing serious deformation of the roadway side, and the large hole spacing leads to a high peak stress between holes, and excessive elastic deformation of the coal accumulation can lead to deformation of the roadway side. A method for determining the spacing between pressure relief holes and anchor holes based on unloading-support synergy is proposed.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for determining the spacing between a pressure relief hole and an anchor hole based on unloading-support coordination, comprising the following steps:

[0008] Step A. Design the optimal spacing between the pressure relief hole and the anchor hole according to the ratio of the pressure relief hole diameter to the anchor hole diameter. First, calculate the crushing zone and plastic zone range R around the pressure relief hole and the anchor hole diameter. d 、R p 、r d 、r p ,in:

[0009]

[0010] Where: R d 、r d are the radius of the crushing zone around the pressure relief hole and the anchor hole, p is the coal body expansion coefficient, r a is the radius of the pressure relief hole, r0 is the radius of the anchor hole;

[0011] described and The unit of is m;

[0012]

[0013] Where: R p 、r p are the radius of the plastic zone around the pressure relief hole and the anchor hole, p0 is the original rock stress, p s is the support resistance, ξ is the coefficient related only to the internal friction angle,

[0014] described and The unit of is m. and The unit is MPa;

[0015] The support resistance p provided by the anchor rod to the tunnel surface through prestress diffusion s Calculated by the following formula (5):

[0016]

[0017] Where: d is the diameter of the anchor rod, σ b is the tensile strength of the anchor rod, n1 and n2 are the anchor rod spacing and row spacing respectively;

[0018] described and The units are all mm. The unit is MPa;

[0019] Step B. Calculate the thickness range of the reinforcement area formed by the anchor bolts. The pressure relief holes loosen the coal body on the roadway surface and form a plastic failure zone. To prevent the pressure relief holes from damaging the reinforcement area formed by the anchor bolts, the distance between the pressure relief holes and the anchor holes is always greater than l. d / 2 or more;

[0020] Step C. Calculate the optimal spacing L between the pressure relief hole and the anchor hole G , L G Substitute into step D to calculate whether the spacing between the pressure relief hole and the anchor hole is coordinated;

[0021] Step D. Establish a numerical model based on the actual relief hole-anchor hole spacing at the on-site working face. Substitute the on-site relief hole-anchor hole spacing and the theoretically calculated optimal spacing into the numerical model to calculate the vertical stress concentration factor K between the holes and the amount of coal body movement D on the side of the roadway, where:

[0022]

[0023] Where: σ max is the peak vertical stress between holes, σ c is the initial ground stress, is the internal friction angle;

[0024] described and The units are all MPa. The unit of is degree;

[0025] Step E: Determine whether the spacing between the pressure relief hole and the anchor hole exerts a synergistic effect ζ based on the stress concentration factor K and the laneway side shift D, where:

[0026]

[0027] Step F. Conduct engineering verification by selecting the average amount of drill cuttings on the side of the tunnel and the state of the anchor stress gauge under different pressure relief hole-anchor hole spacing conditions on the working face to determine whether the pressure relief holes and anchor holes play a synergistic role;

[0028] The early warning value of the amount of drill cuttings on the working face is D L , the average amount of cuttings is D c , the anchor stress gauge value is F v ,but:

[0029]

[0030] As a further description of the above technical solution: the anchor rods are arranged radially at a certain interval along the roadway. When the surrounding rock deforms, the anchor rods will exert compressive stress on the surrounding rock. Each anchor rod will form a conical compression zone that connects and overlaps with each other to form a uniform continuous compression zone, namely, an extrusion reinforcement arch, wherein:

[0031]

[0032] Where: L D is the anchor length, L d is the thickness of the reinforced arch, l d is the shortest distance between the reinforcement arch and the tunnel surface, a is the anchor spacing, then l d =(L D -L d ) / 2;

[0033] described and The unit is m.

[0034] As a further description of the above technical solution: the optimal spacing between the pressure relief hole and the anchor hole is determined by formulas (3) and (4) to be the intersection of the plastic zones of the two. When the plastic zones of the pressure relief hole and the anchor hole are connected to each other, a dual-effect structure of unloading and support synergy will be formed, which can prevent and control the occurrence of rock burst to the greatest extent. However, in a few projects, the plastic zone and elastic zone between the pressure relief hole and the anchor hole are not connected to each other, and there is still a part of the original rock stress zone between the two. At this time, the pressure relief structure has little effect on the transfer and energy dissipation of coal body stress, which will cause most of the transferred stress to accumulate in this area to form a stress concentration zone, resulting in insufficient pressure relief. In addition, when the crushing zone of the pressure relief hole and the anchor hole is connected to each other, it is excessive pressure relief. Therefore, the calculation formula of the pressure relief hole-anchor hole spacing is:

[0035] R d +r d ≤L≤R p +r p +R d +r d (7).

[0036] As a further description of the above technical solution: Since the plastic zone range and the crushing zone range of the anchor hole are basically the same and much smaller than the pressure relief hole, when the spacing L only meets R d +r d ≤L≤2R d When the distance between the pressure relief hole and the anchor hole is too small, the pressure relief is excessive, which may lead to support failure. The range of the spacing L can be calculated by the following formula:

[0037] 2R d ≤L≤R p +r p +R d +r d (8).

[0038] As a further description of the above technical solution: the optimal spacing L between the pressure relief hole and the anchor hole GTake the average value of the L range. To avoid excessive pressure relief caused by too small a spacing between the pressure relief hole and the anchor hole, which may lead to support failure, the spacing L should always be greater than l d / 2 means:

[0039]

[0040] As a further description of the above technical solution: after redesigning the spacing between the pressure relief holes and the anchor holes, when the indicator ξ meets the synergistic effect, the depth, spacing and diameter of the pressure relief holes are adjusted according to the actual production conditions on site to achieve a better synergistic anti-impact effect of the pressure relief holes and the anchor holes.

[0041] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0042] 1. In the present invention, by using numerical simulation software, the stress concentration coefficient between adjacent pressure relief holes and anchor holes and the amount of coal body movement in the roadway are calculated to determine whether the hole spacing has a synergistic effect. There is no need for on-site measured data, which saves corresponding testing time. Theoretical calculations can guide the hole spacing design in the on-site production process, which has reference value in the field of technical methods for preventing and controlling rock burst.

[0043] 2. In the present invention, by calculating the crushing zone, plastic zone range and anchor support reinforcement zone range around the pressure relief hole-anchor hole, the hole spacing is limited by these areas, thereby avoiding the phenomenon of reduced anchor support bearing capacity due to too small hole spacing or large stress concentration coefficient between holes due to too large hole spacing. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a flow chart of a method for determining the spacing between pressure relief holes and anchor holes based on unloading-supporting coordination proposed by the present invention;

[0045] Figure 2 Schematic diagram of the mechanical model for optimizing the matching of pressure relief holes and anchor holes in a method for determining the spacing between pressure relief holes and anchor holes based on unloading-supporting coordination proposed in the present invention;

[0046] Figure 3 This is a schematic diagram of the anchor rod extrusion reinforcement range in a method for determining the spacing between relief holes and anchor holes based on relief-support coordination proposed by the present invention;

[0047] Figure 4 This is a diagram showing the relationship between the pressure relief holes and anchor holes in a method for determining the spacing between pressure relief holes and anchor holes based on unloading-supporting coordination proposed in the present invention;

[0048] Figure 5 A curve diagram of the vertical stress peak value between holes under different hole spacing conditions in a method for determining the spacing between relief holes and anchor holes based on unloading-supporting coordination proposed by the present invention;

[0049] Figure 6 Schematic diagram of a numerical simulation calculation model for a method for determining the spacing between relief holes and anchor holes based on unloading-support coordination proposed in the present invention;

[0050] Figure 7 Schematic diagram of average drilling cuttings of coal body according to the method for determining the spacing between relief holes and anchor holes based on the coordination of relief and anchoring proposed by the present invention;

[0051] Figure 8 This is a schematic diagram of the anchor stress gauge measurement value in the method for determining the spacing between the stress relief hole and the anchor hole based on unloading-support coordination proposed by the present invention.

[0052] Legend:

[0053] 1. Pressure relief hole; 2. Boundary of the plastic zone of the pressure relief hole; 3. Boundary of the elastic zone of the pressure relief hole; 4. Anchor hole; 5. Boundary of the plastic zone of the anchor hole; 6. Boundary of the elastic zone of the anchor hole; 7. Coal body; 8. Anchor rod; 9. Plastic zone of the pressure relief hole; 10. Anchor rod extrusion reinforcement zone; 11. Crushing zone around the hole; 12. Sandy mudstone; 13. Coal seam; 14. Excavation tunnel; 15. Medium-fine sandstone. DETAILED DESCRIPTION

[0054] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0055] Combine Figures 1 to 5 As shown, the specific implementation of the method for determining the spacing between the pressure relief hole and the anchor hole based on the coordination of the pressure relief hole and the anchor hole provided by the present invention is described.

[0056] The existing parameters of pressure relief holes and anchor holes are usually constructed with unified specifications. In different impact risk areas, pressure relief holes are denser or anchor rods are added to reduce the possibility of impact ground pressure. However, there is little quantitative analysis of the specific spacing between pressure relief holes and anchor holes. For this problem, this technical solution determines whether the pressure relief holes and anchor holes have a synergistic effect by analyzing the stress concentration coefficient between holes and the amount of laneway side shift under the current pressure relief hole-anchor hole spacing conditions. If the stress concentration coefficient between holes is too large or the amount of laneway side shift is too large, the pressure relief hole-anchor hole spacing is redesigned through theoretical calculation. The optimal spacing between anchor holes and pressure relief holes is studied under the conditions of crushing and plastic zones around the pressure relief holes and anchor holes. In order to prevent the anchor support from failing due to too small a hole spacing, the anchor support reinforcement zone is introduced to limit the optimal spacing between the two holes. The stress distribution law between holes is analyzed and the practicability of the new method is verified by combining finite element numerical simulation software. The results show that:

[0057] (1) The calculation of the optimal spacing between the pressure relief holes and the anchor holes is to determine a balance point so that the pressure relief holes and the anchor support can work together. At this balance point, both a good pressure relief effect can be achieved and the damage to the support structure can be minimized.

[0058] (2) When the distance between the pressure relief hole and the anchor hole is less than the optimal spacing, the vertical stress of the coal body between the holes does not decrease significantly with the decrease of the hole spacing, the plastic zone around the pressure relief hole destroys the anchor support area, and the peak value of the vertical stress between adjacent holes increases nonlinearly with the increase of the hole spacing;

[0059] (3) The stress concentration coefficient between holes and the amount of laneway side shifting are used to determine whether the synergistic effect is achieved under the current stress relief hole-anchor hole spacing conditions. When the stress relief hole-anchor hole spacing is close to the theoretically calculated optimal spacing, the stress concentration coefficient between holes is low and the amount of laneway side shifting is small.

[0060] After field practice, the diameter of most anchor holes is 20mm, the spacing is within the range of 800-1000mm, and the diameter of the pressure relief holes is within the range of 100-300mm, that is, the pressure relief hole-anchor hole diameter ratio is between 5-15, and the pressure relief hole spacing is divided into 1-3m according to the regional impact hazard. Taking the strong impact hazard area as an example, the pressure relief hole spacing is 1m. After the pressure relief holes and anchor holes are constructed in the coal body, the pressure relief holes transfer the high energy accumulation area in the shallow part of the tunnel surrounding rock to the deep part, forming a buffer energy absorption area in the shallow area of ​​the tunnel surrounding rock, and the anchor support reinforces the shallow area of ​​the tunnel surrounding rock, forming a strong dynamic effect blocking area in the shallow area of ​​the tunnel surrounding rock. However, the pressure relief measures It often destroys the integrity of the roadway side and reduces the bearing capacity of the guard body. When the spacing between the pressure relief hole and the anchor hole is less than a certain critical value, it may cause excessive pressure relief, that is, damage the strong structure of the anchor support, resulting in a decrease in the strength of the anchor support. How to effectively relieve the pressure on the coal roadway side while ensuring that the strength of the anchor support structure is not reduced has become a contradiction. Therefore, it is necessary to determine a balance point so that the spacing between the pressure relief hole and the anchor hole can be coupled with each other to achieve the purpose of coordinated prevention and control. At this balance point, it can not only meet a better pressure relief effect, but also minimize the degree of damage to the anchor support structure. In order to solve this problem, the present invention provides a method for determining the spacing between the pressure relief hole and the anchor hole based on unloading-support coordination.

[0061] Taking the actual working face of a mine as an example, the design method of the spacing between pressure relief holes and anchor holes based on the synergistic effect of unloading and support is further explained. The specific steps include:

[0062] The two sides of a certain mine working face are supported by anchor bolts. The anchor bolts are MG-500 / 20×2200 left-handed fully threaded steel anchor bolts with an anchoring force of no less than 160kN. The spacing between anchor bolts is 900×900mm, with 5 anchor bolts in each row. The anchor bolts have a diameter of 20mm and a length of 2100mm. The pressure relief holes are arranged horizontally in a single row with a diameter of 200mm and a hole depth of 20m. The spacing between the pressure relief holes and the anchor holes is calculated based on the condition of tunnel surrounding rock failure, i.e. 0.35m and 0.55m.

[0063] Step A. Design the optimal spacing between the pressure relief hole and the anchor hole according to the ratio of the pressure relief hole diameter to the anchor hole diameter. First, calculate the crushing zone and plastic zone range R around the pressure relief hole and the anchor hole diameter. d 、R p 、r d 、r p ,in:

[0064]

[0065]

[0066] Where: R d 、r dare the radius of the crushing zone around the pressure relief hole and the anchor hole, p is the coal body expansion coefficient, r a is the radius of the pressure relief hole, r0 is the radius of the anchor hole;

[0067] described and The unit of is m;

[0068]

[0069] Where: R p 、r p are the radius of the plastic zone around the pressure relief hole and the anchor hole, p0 is the original rock stress, p s is the support resistance, ξ is the coefficient related only to the internal friction angle,

[0070] described and The unit of is m. and The unit is MPa;

[0071] The support resistance p provided by the anchor rod to the tunnel surface through prestress diffusion s Calculated by the following formula (5):

[0072]

[0073] Where: d is the diameter of the anchor rod, σ b is the tensile strength of the anchor rod, n1 and n2 are the anchor rod spacing and row spacing respectively;

[0074] described and The units are all mm. The unit is MPa;

[0075] Step B. Calculate the thickness range of the reinforcement area formed by the anchor bolts. The pressure relief holes loosen the coal body on the roadway surface and form a plastic failure zone. To prevent the pressure relief holes from damaging the reinforcement area formed by the anchor bolts, the distance between the pressure relief holes and the anchor holes is always greater than l. d / 2 or more;

[0076] The anchor rods are arranged radially along the roadway at a certain interval. When the surrounding rock deforms, the anchor rods will exert compressive stress on the surrounding rock. Each anchor rod will form a conical compression zone that connects and overlaps with each other to form a uniform continuous compression zone, namely, an extrusion reinforcement arch, in which:

[0077]

[0078] Where: L D is the anchor length, L d is the thickness of the reinforced arch, ld is the shortest distance between the reinforcement arch and the tunnel surface, a is the anchor spacing, then l d =(L D -L d ) / 2;

[0079] described and The unit of is m;

[0080] Step C. Calculate the optimal spacing L between the pressure relief hole and the anchor hole G , L G Substitute into step D to calculate whether the spacing between the pressure relief hole and the anchor hole is coordinated;

[0081] The optimal spacing between the pressure relief hole and the anchor hole is determined by formulas (3) and (4) to be the intersection of their plastic zones. When the plastic zones of the pressure relief hole and the anchor hole are connected, a dual-effect structure of unloading and support coordination is formed, which can prevent and control the occurrence of rock burst to the greatest extent. However, in a few projects, the plastic zone and elastic zone between the pressure relief hole and the anchor hole are not connected to each other, and there is still a part of the original rock stress zone between the two. At this time, the pressure relief structure has little effect on the transfer and energy dissipation of coal body stress, which will cause most of the transferred stress to accumulate in this area to form a stress concentration zone, resulting in insufficient pressure relief. In addition, when the crushing zone of the pressure relief hole and the anchor hole is connected to each other, it is excessive pressure relief. Therefore, the calculation formula of the pressure relief hole-anchor hole spacing is:

[0082] R d +r d ≤L≤R p +r p +R d +r d (7)

[0083] 2R d ≤L≤R p +r p +R d +r d (8)

[0084] Optimal spacing L between pressure relief hole and anchor hole G Take the average value of the L range. To avoid excessive pressure relief caused by too small a spacing between the pressure relief hole and the anchor hole, which may lead to support failure, the spacing L should always be greater than l d / 2 means:

[0085]

[0086] The optimal spacing between the pressure relief hole and the anchor hole under different aperture ratios is listed in the following table:

[0087] Table 1 Parameter analysis scheme

[0088]

[0089] After redesigning the spacing between the pressure relief holes and anchor holes, when the indicator ξ meets the synergistic effect, the depth, spacing, and diameter of the pressure relief holes are adjusted according to the actual production conditions on site to achieve a better synergistic anti-collision effect between the pressure relief holes and anchor holes;

[0090] Step D. Establish a numerical model based on the actual relief hole-anchor hole spacing at the on-site working face. Substitute the on-site relief hole-anchor hole spacing and the theoretically calculated optimal spacing into the numerical model to calculate the vertical stress concentration factor K between the holes and the amount of coal body movement D on the side of the roadway, where:

[0091]

[0092] Where: σ max is the peak vertical stress between holes, σ c is the initial ground stress, is the internal friction angle;

[0093] described and The units are all MPa. The unit of is degree;

[0094] Step E: Determine whether the spacing between the pressure relief hole and the anchor hole exerts a synergistic effect ζ based on the stress concentration factor K and the laneway side shift D, where:

[0095]

[0096] Step F. Conduct engineering verification by selecting the average amount of drill cuttings on the side of the tunnel and the state of the anchor stress gauge under different pressure relief hole-anchor hole spacing conditions on the working face to determine whether the pressure relief holes and anchor holes play a synergistic role;

[0097] The early warning value of the amount of drill cuttings on the working face is D L , the average amount of cuttings is D c , the anchor stress gauge value is F v ,but:

[0098]

[0099]

[0100] Under the condition of the aperture ratio of 10, the spacing between the pressure relief hole and the anchor hole of the working face is 0.35m, 0.45m, and 0.55m respectively. The average drilling cuttings of the coal body and the anchor stress gauge value are measured respectively. The drilling cuttings warning value is 4.6kg / m. The average drilling cuttings of the coal body is as follows: Figure 7 As shown, the anchor stress gauge value is as follows Figure 8 As shown by Figure 7 and Figure 8 It can be seen that when the hole spacing is 0.35m, the average amount of drilled cuttings in the coal body is 1.54kg / m, but the anchor stress gauge value drops to 42kN on the 13th day. When the hole spacing is 0.55m, the average amount of drilled cuttings in the coal body is 2.3kg / m, and the anchor stress gauge value does not change. When the hole spacing is 0.45m, the average amount of drilled cuttings in the coal body is 1.96kg / m, and the anchor stress gauge value does not change. When the hole spacing is 0.45m, the average amount of drilled cuttings in the coal body is low, the coal body is in a low stress state, fully unloaded, and the anchor stress gauge value does not change. The unloading hole has little damage to the anchor. When the hole spacing is 0.35m, although the average amount of drilled cuttings is low, the anchor stress gauge value drops, indicating that the unloading hole has more serious damage to the anchor, reducing the bearing capacity of the anchor. When the hole spacing is 0.55m, the increase in drilled cuttings is higher than that when the hole spacing is 0.45m, and the coal stress is higher.

[0101] In summary, the hole spacing of 0.35m between the pressure relief hole and the anchor hole meets the indicators {ζ_2, ξ_3}, the hole spacing of 0.45m between the pressure relief hole and the anchor hole meets the indicators {ζ_1, ξ_1}, and the hole spacing of 0.35m between the pressure relief hole and the anchor hole meets the indicators {ζ_2, ξ_1}. Therefore, the hole spacing of 0.45m is the optimal choice.

[0102] A method for designing the spacing between relief holes and anchor holes based on the synergistic effect of relief and support was developed through theoretical calculations, numerical simulations, and subsequent graphical and data analysis. Under anchor support conditions that fully consider the influence of the plastic zone of the relief holes, the optimal spacing between relief holes and anchor holes was determined for different hole diameter ratios. This method avoids anchor support failure caused by too small a spacing between holes or a high stress concentration factor in the coal mass caused by too large a spacing between holes. This method provides guidance for the prevention and control of rock bursts, further ensuring safe production in coal mines.

[0103] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for designing the spacing between pressure relief holes and anchor holes based on the unloading-supporting synergistic effect, characterized in that the steps include: Step A. Design the optimal spacing between the pressure relief hole and the anchor hole according to the ratio of the pressure relief hole diameter to the anchor hole diameter. First, calculate the range of the crushing zone and the plastic zone around the pressure relief hole and the anchor hole. 、 、 、 ,in: （1）； （2）； Where: 、 are the radius of the crushing zone around the pressure relief hole and anchor hole, is the coal mass expansion coefficient, is the radius of the pressure relief hole, is the radius of the anchor hole; described 、 、 and The unit of is m; （3）； （4）； Where: 、 are the plastic zone radii around the pressure relief hole and anchor hole, is the original rock stress, is the support resistance, is the coefficient related only to the internal friction angle, ; described and The unit of is m. and The unit is MPa; The support resistance provided by the anchor rod to the tunnel surface through prestress diffusion Calculated by the following formula (5): （5）； Where: is the anchor diameter, is the tensile strength of the anchor rod, 、 Specifically, the anchor spacing and row spacing; described 、 ,and The units are all mm. The unit is MPa; Step B. Calculate the thickness range of the anchor reinforcement area. The pressure relief holes loosen the coal body on the roadway surface and form a plastic failure zone. To prevent the pressure relief holes from damaging the reinforcement area formed by the anchor, the distance between the pressure relief holes and the anchor holes is always greater than above; Step C. Calculate the optimal spacing between the pressure relief hole and the anchor hole ,Will Substitute into step D to calculate whether the spacing between the pressure relief hole and the anchor hole is coordinated; Step D. Establish a numerical model based on the actual relief hole-anchor hole spacing on the working surface. Substitute the on-site relief hole-anchor hole spacing and the theoretically calculated optimal spacing into the numerical model to calculate the vertical stress concentration factor between the holes. , the amount of coal body moving closer to the road side ,in: （10）； Where: is the peak vertical stress between holes, is the initial ground stress, , is the internal friction angle; described and The units are all MPa. The unit of is degree; Step E. Based on the stress concentration factor and lane side movement Determine whether the spacing between the pressure relief hole and the anchor hole has a synergistic effect ,in: ； Step F. Conduct engineering verification by selecting the average amount of drill cuttings on the side of the tunnel and the state of the anchor stress gauge under different pressure relief hole-anchor hole spacing conditions on the working face to determine whether the pressure relief holes and anchor holes play a synergistic role; The early warning value of the amount of drill cuttings on the working face is The average amount of cuttings is , the anchor stress gauge value is ,but: ； The anchor rods are arranged radially along the roadway at a certain interval. When the surrounding rock deforms, the anchor rods will exert compressive stress on the surrounding rock. Each anchor rod will form a conical compression zone that connects and overlaps with each other to form a uniform continuous compression zone, namely, an extrusion reinforcement arch, wherein: （6）； Where: is the anchor rod length, To reinforce the arch thickness, To strengthen the closest distance between the arch and the tunnel surface, is the anchor spacing, then ; described 、 、 and The unit of is m; The optimal spacing between the pressure relief hole and the anchor hole is determined by formulas (3) and (4) to be the intersection of their plastic zones. When the plastic zones of the pressure relief hole and the anchor hole are connected, a dual-effect structure of unloading and support coordination is formed, which can prevent and control the occurrence of rock burst to the greatest extent. However, in a few projects, the plastic zone and elastic zone between the pressure relief hole and the anchor hole are not connected to each other, and there is still a part of the original rock stress zone between the two. At this time, the pressure relief structure has little effect on the transfer and energy dissipation of coal body stress, which will cause most of the transferred stress to accumulate in this area to form a stress concentration zone, resulting in insufficient pressure relief. In addition, when the crushing zone of the pressure relief hole and the anchor hole is connected to each other, it is excessive pressure relief. Therefore, the calculation formula of the pressure relief hole-anchor hole spacing is: （7）； Since the plastic zone range of the anchor hole is basically the same as the crushing zone range and is much smaller than the pressure relief hole, when the spacing L only meets When the distance between the pressure relief hole and the anchor hole is too small, the pressure relief is excessive, which may lead to support failure. The range of the spacing L can be calculated by the following formula: （8）； Optimal spacing between pressure relief holes and anchor holes Take the average value of the L range to avoid excessive pressure relief caused by too small a spacing between the pressure relief hole and the anchor hole, which may lead to support failure. Should always be greater than Right now: （9）。 2. The method for designing the spacing between pressure relief holes and anchor holes based on the unloading-supporting synergistic effect according to claim 1, characterized in that: After redesigning the spacing between the pressure relief hole and the anchor hole, the indicator When the synergistic effect is met, the depth, spacing and diameter of the pressure relief holes are adjusted according to the actual production conditions on site to achieve a better synergistic anti-impact effect of the pressure relief holes and anchor holes.

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