A large-diameter borehole pressure relief method in a high horizontal stress area of regional structure

Abstract

A large-diameter borehole pressure relief method for high-level stress areas in regional structures, comprising the steps of: (1) exploring the stress state of the roadway side through in-situ stress testing methods, determining the stress concentration state and distribution law of the roadway side, and obtaining the direction of the maximum horizontal principal stress; (2) determining the construction direction of the pressure relief borehole according to the direction of the maximum horizontal principal stress obtained in step (1), and the construction direction of the pressure relief borehole is perpendicular to the direction of the maximum horizontal principal stress; (3) determining the construction parameters of the pressure relief borehole according to the geological conditions and stress environment factors in the area where the coal seam is located, and based on the construction direction of the pressure relief borehole determined in step (2), the construction parameters of the pressure relief borehole include the depth of the pressure relief borehole, the diameter of the pressure relief borehole, the spacing of the pressure relief boreholes, and the arrangement method of the pressure relief boreholes; for the spacing of the pressure relief boreholes in high-level stress areas, it is determined according to the impact hazard level. This method can maximize the deformation of the boreholes, achieve the best pressure relief effect, and reduce the impact hazard of the coal body in the working face.

Description

Technical Field

[0001] The present invention relates to a method for relieving pressure by large-diameter drilling in a high-level stress area of regional structure, belonging to the technical field of coal mine safety. Background Art

[0002] With the increasing demand for coal, the intensity of coal mining has gradually increased, and many mining areas have gradually shifted to deep mining. After the coal mine enters deep mining, the coal and rock mass is in a high-level stress state for a long time, and its internal structure and behavioral characteristics have changed, which is likely to cause accidents such as rock bursts, seriously restricting the safe production of coal mines.

[0003] Coal seam pressure relief blasting and large-diameter borehole pressure relief are the main methods for preventing coal body impact in the working face. The disturbance generated by coal seam pressure relief blasting changes the static load of the coal body, and the pressure relief time is short. The cracks will be recompacted within a period of time, and the stress state will be restored again, so the pressure relief effect is not obvious. The large-diameter borehole pressure relief technology forms a weakening area inside the shallow surrounding rock of the roadway by means of artificial drilling, transfers the high stress around it to the deep stable surrounding rock, and at the same time provides a compensation space for the swelling deformation of the surrounding rock to reduce the roadway deformation. The disturbance generated by the borehole pressure relief construction will cause cracks in the surrounding rock of the borehole, resulting in stress redistribution. The borehole deformation will cause the surrounding rock to break and stress redistribution, achieving the pressure relief effect.

[0004] As a kind of in-gallery stress transfer technology, when performing large-diameter borehole pressure relief, in order to ensure that the drilling rig has enough working space, it is necessary to move the fully mechanized heading equipment backward a certain distance and construct alternately, resulting in low operation efficiency. In addition, since the traditional borehole pressure relief constructs pressure relief boreholes perpendicular to the two sides of the roadway through the drilling rig, the pressure relief boreholes are not easy to deform and cannot reduce the maximum horizontal principal stress to the greatest extent, and the pressure relief effect is not ideal. Summary of the Invention

[0005] Aiming at the problems existing in the above-mentioned prior art, the present invention provides a method for relieving pressure by large-diameter drilling in a high-level stress area of regional structure, which can maximize the deformation of the borehole, achieve the best pressure relief effect, and reduce the impact risk of the coal body in the working face.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a method for relieving pressure by large-diameter drilling in a high-level stress area of regional structure, including the following steps:

[0007] (1) Explore the stress state of the roadway side through the in-situ stress test method, determine the stress concentration state and distribution law of the roadway side, and obtain the direction of the maximum horizontal principal stress;

[0008] (2) According to the direction of the maximum horizontal principal stress obtained in step (1), calculate the construction direction of the pressure relief borehole, and the construction direction of the pressure relief borehole is perpendicular to the direction of the maximum horizontal principal stress;

[0009] (3) According to the geological conditions and stress environment factors in the area where the coal seam is located, and based on the construction direction of the pressure-relief boreholes determined in step (2), determine the construction parameters of the pressure-relief boreholes. The construction parameters of the pressure-relief boreholes include the depth of the pressure-relief boreholes, the diameter of the pressure-relief boreholes, the spacing of the pressure-relief boreholes, and the layout method of the pressure-relief boreholes. For the spacing of the pressure-relief boreholes in the high horizontal stress area, it is also necessary to determine according to the impact hazard level.

[0010] Furthermore, in step (1), the direction of the maximum horizontal principal stress is measured by the stress relief method for in-situ stress measurement. The measurement system adopts the hollow inclusion strain gauge method of the borehole wall deformation method, specifically as follows:

[0011] 201) Use a sleeve borehole or a cut groove in the rock mass of the chamber or roadway to separate part of the rock sample from the surrounding rock. Monitor and record the strain value of the rock sample through a strain gauge. According to the existing stress-strain relationship and the elastic modulus of the rock sample, obtain the magnitude and direction of the in-situ stress at the measuring point.

[0012] 202) According to the magnitude and direction of the in-situ stress at the measuring point obtained in step 201), there will be two principal stresses in the nearly horizontal direction at each measuring point, indicating that the horizontal tectonic stress dominates. Use the least squares linear fitting to perform a regression analysis on the stress values of each measuring point, and obtain the fitting formula between the maximum horizontal principal stress at the measuring point and the buried depth of the measuring point as follows:

[0013] σ h，max = mH + n;

[0014] Among them, σ h，max is the maximum horizontal principal stress at the measuring point; H is the buried depth of the measuring point; m and n are constants, and unique values are obtained through the least squares fitting line.

[0015] Furthermore, in step (2), in the high horizontal stress area, let the angle between the maximum horizontal principal stress and the axial direction of the roadway be α, then the calculation formula for determining the angle between the construction direction of the pressure-relief borehole and the axial direction of the roadway is:

[0016] γ = α + 90°.

[0017] Furthermore, in step (3), the impact hazard level is divided into a weak impact hazard area, a medium impact hazard area, and a strong impact hazard area through impact hazard assessment.

[0018] Furthermore, in step (3), the construction requirement for the depth of the pressure-relief borehole to meet the minimum impact hazard index is as follows: The attenuation of energy is in a power-law relationship with the propagation distance. For simplified analysis, without considering the difference in energy attenuation, the calculation formula for the impact hazard index after borehole pressure relief is obtained as:

[0019]

[0020] Wherein, a 1 is the area of the first high-stress region, with the unit of m 2 ; l 1 is the distance between the center of the first high-stress region and the roadway side; a 2 is the area of the second high-stress region, with the unit of m 2 ; l 2 is the distance between the center of the second high-stress region and the roadway side, with the unit of m; when the relief borehole satisfies the minimum impact risk index, the relief effect is the most obvious;

[0021] The diameter of the relief borehole is taken as 110 mm;

[0022] The construction requirement for the spacing of the relief boreholes to form a weakening region around each borehole is as follows: when large-diameter borehole relief is carried out in the high horizontal stress area, a stress reduction area is formed on one side of each borehole. After the stress reduction areas are interconnected, a whole-through coal body softening area is formed, which is the weakening region;

[0023] The construction requirement for the layout method of the relief boreholes to satisfy the superposition of the relief circles and ensure the relief range is as follows: when a single-row borehole layout is adopted, a stress reduction area is formed around each borehole, and the stress reduction areas around each borehole are connected to form a larger stress reduction area.

[0024] The present invention explores the stress state of the roadway side through the in-situ stress testing method, determines the stress concentration state and distribution law of the roadway side. After obtaining the direction of the maximum horizontal principal stress, the construction direction of the relief borehole is determined, and it is ensured that the construction direction of the relief borehole is always perpendicular to the direction of the maximum horizontal principal stress, so that the relief borehole deforms to the greatest extent, achieving the best effect of large-diameter borehole relief in the high horizontal stress area, and greatly reducing the impact risk of the coal body in the working face. Description of the Drawings

[0025] Figure 1 is a schematic diagram for determining the construction of the relief borehole in the present invention;

[0026] Figure 2 is Figure 1 the sectional schematic diagram in the A-A direction of

[0027] In the figure: 1, roadway side; 2, maximum horizontal principal stress; 3, relief borehole; 4, roadway; 5, roadway floor. Detailed Embodiments

[0028] The present invention will be further described below in conjunction with the drawings.

[0029] As Figure 1 shown, a large-diameter borehole relief method for the high horizontal stress area of regional structure includes the following steps:

[0030] (1) Explore the stress state of roadway rib 1 through in-situ stress testing methods, determine the stress concentration state and distribution law of roadway rib 1, and obtain the direction of the maximum horizontal principal stress 2;

[0031] (2) According to the direction of the maximum horizontal principal stress obtained in step (1), calculate the construction direction of the pressure relief borehole 3, and the construction direction of the pressure relief borehole is perpendicular to the direction of the maximum horizontal principal stress;

[0032] (3) According to the geological conditions and stress environment factors in the area where the coal seam is located, and based on the construction direction of the pressure relief borehole determined in step (2), determine the construction parameters of the pressure relief borehole. The construction parameters of the pressure relief borehole include the depth of the pressure relief borehole, the diameter of the pressure relief borehole, the spacing of the pressure relief boreholes, and the layout method of the pressure relief boreholes; for the spacing of the pressure relief boreholes in the high horizontal stress area, it is also necessary to determine according to the impact hazard level.

[0033] Further, in step (1), the direction of the maximum horizontal principal stress is measured by the stress relief method for in-situ stress measurement, and the measurement system adopts the hollow inclusion strain gauge method of the borehole wall deformation method. Specifically:

[0034] 201) In the rock mass of the chamber or roadway, use a sleeve borehole or a cut groove to separate part of the rock sample from the surrounding rock, monitor and record the strain value of the rock sample through a strain gauge, and obtain the magnitude and direction of the in-situ stress at the measurement point according to the existing stress-strain relationship and the elastic modulus of the rock sample;

[0035] 202) According to the magnitude and direction of the in-situ stress at the measurement point obtained in step 201), there will be two principal stresses in the nearly horizontal direction at each measurement point, indicating that the horizontal tectonic stress dominates. Use the least squares linear fitting to perform a regression analysis on the stress values of each measurement point, and obtain the fitting formula of the maximum horizontal principal stress at the measurement point and the buried depth of the measurement point as follows:

[0036] σ h，max =mH + n;

[0037] Among them, σ h，max is the maximum horizontal principal stress at the measurement point; H is the buried depth of the measurement point; m and n are constants, and unique values are obtained through the least squares fitting line.

[0038] Further, in step (2), in the high horizontal stress area, let the included angle between the maximum horizontal principal stress and the axial direction of the roadway 4 be α, then the calculation formula for determining the included angle between the construction direction of the pressure relief borehole and the axial direction of the roadway is:

[0039] γ = α + 90°.

[0040] Further, in step (3), the impact hazard level is divided into a weak impact hazard area, a medium impact hazard area, and a strong impact hazard area through impact hazard assessment.

[0041] Furthermore, in the step (3), the construction requirement for the depth of the pressure relief borehole to satisfy the determination method with the minimum impact risk index is as follows: The attenuation of energy has a power relationship with the propagation distance. For the sake of simplified analysis, without considering the energy attenuation difference, the calculation formula for the impact risk index after borehole pressure relief is obtained as follows:

[0042]

[0043] In the formula, a 1 is the area of the high-stress area 1, with the unit of m 2 ; l 1 is the distance between the center of the high-stress area 1 and the roadway side, taking 12 m; a 2 is the area of the high-stress area 2, with the unit of m 2 ; l 2 is the distance between the center of the high-stress area 2 and the roadway side, with the unit of m; when the pressure relief borehole 3 satisfies the minimum impact risk index, the pressure relief effect is the most obvious;

[0044] The diameter of the pressure relief borehole is taken as 110 mm;

[0045] The construction requirement for the spacing of the pressure relief boreholes to satisfy the determination process of the weakening area formed around each borehole is as follows: When large-diameter borehole pressure relief is carried out in the high horizontal stress area, a stress reduction area is formed on one side of each borehole. After the stress reduction areas are interconnected, a globally continuous coal body softening area is formed, which is the weakening area;

[0046] The construction requirement for the layout method of the pressure relief boreholes to satisfy the process of the pressure relief circles overlapping and ensuring the pressure relief range is as follows: The single-row borehole layout is adopted, and a stress reduction area is formed around each single borehole. The stress reduction areas around each borehole are connected to form a larger stress reduction area.

[0047] It is determined that the direction of the pressure relief borehole is perpendicular to the direction of the maximum horizontal principal stress. In the actual production process, parameters should be reasonably set according to the actual situation of the coal mine. For the high horizontal stress area with a complex stress environment, the above steps should be repeated to determine the construction direction of the pressure relief borehole, reduce the waste of the project and the consumption of manpower, and at the same time ensure that the pressure relief borehole is most likely to deform and achieve the best pressure relief effect.

[0048] The principle of the influence of the large-diameter pressure relief borehole of the present invention on the coal body stress is as follows: The roof rock layer acts on the coal body, and the pressure on the coal body in front of the working face is represented by the curve σ z ; σ k represents the ultimate stress value for rock burst occurrence, that is, when the stress of the coal seam reaches this value, rock burst will occur. Starting from the coal wall, the overlying stress of the coal seam reaches the maximum value σ zmaxand this value is close to the ultimate stress value, indicating a very high risk of rock burst. In this case, a borehole with a diameter d = 2r and a length of l is used, and the length of the squeezed part in the middle of the borehole is a, resulting in a pressure drop of the borehole coal mass to σ sc . The stress σ z The higher it is, the greater the degree of squeezing and movement of the borehole. In the abutment pressure area, large-diameter boreholes are used for pressure relief to reduce its stress value, and small stress concentrations σ’ z appear in a local range of the borehole. When σ’ z exceeds the strength of the borehole wall, over time, the weathering and fracturing of the coal mass between the boreholes cause pressure relief within a range with a diameter of D around each borehole. Therefore, when arranging the boreholes, the spacing S is at least equal to D, so that within a certain range, the stress is reduced.

[0049] It is determined that the construction direction of the pressure relief borehole is perpendicular to the direction of the maximum horizontal principal stress. At this time, the pressure relief hole can undergo the maximum degree of deformation, and at the same time, it can also cause fracture cracks in the rock mass, achieving the best pressure relief effect and fully reducing the impact risk.

[0050] Embodiment:

[0051] As Figure 1 and Figure 2 shown, the area about 150 m in front of the 37221 working face of a certain mine is the abutment pressure area, which is a multi-occurrence area of rock burst and is the key area for prevention and control. It is ensured that in the area with the risk of rock burst, stress information in front of the working face is collected in a timely manner by means of on-line stress monitoring, drilling cuttings method, etc., and large-diameter borehole pressure relief is carried out in the area about 150 m in front of the working face in the dangerous area. After the impact risk assessment, it is determined as a strong impact risk area, and it is determined to implement large-diameter borehole pressure relief. Based on the stress environment of this working face, the large-diameter borehole pressure relief parameters of the present invention are determined, and the specific implementation steps are as follows:

[0052] (1) Explore the stress state of the roadway side by the stress relief method in the in-situ stress test method, determine the stress concentration state and distribution law of the roadway side, and obtain that the included angle between the direction of the maximum horizontal principal stress and the roadway axis is 45 degrees. By the stress relief method, the magnitude and direction of the in-situ stress of the measuring point are obtained, and the least squares linear fitting is used to perform regression analysis on the stress values of each measuring point, and the fitting formula of the direction of the maximum horizontal principal stress of the measuring point and the buried depth of the measuring point is determined as:

[0053] σ h，max = 0.046H + 0.714;

[0054] The calculation formula for determining the included angle between the construction direction of the pressure relief borehole and the roadway axis is:

[0055] γ = 45° + 90° = 135°;

[0056] (2) After monitoring the working face area by the drill cuttings method, the pulverized coal exceeded the standard, and there was a risk of rock burst. According to the calculation formula of the impact risk index after borehole pressure relief, when the borehole depth was 17 m, the borehole depth met the minimum impact risk index and complied with the safety code requirements;

[0057] The borehole diameter was 110 mm;

[0058] The construction requirement of the borehole spacing was that when a weakening area was formed around each borehole, the borehole spacing was 0.8 m, and the distance from the roadway floor was 1.2 - 1.8 m;

[0059] Based on the above-determined pressure relief borehole construction direction, borehole depth, and borehole diameter, determine the position of the pressure relief boreholes and carry out the construction of the pressure relief boreholes. Due to the influence of geological structures on this working face and the complex stress environment, when drilling boreholes in other areas of this working face, the maximum principal stress in the new area space should be repeatedly determined, and the above steps should be repeated for continuous construction. After the construction of the pressure relief boreholes, monitor and inspect the rock burst risk in the pressure relief area again to ensure that the drill cuttings do not exceed the standard and the pressure relief boreholes do not deform or rupture, so as to achieve the best pressure relief effect and reduce the impact risk of the coal body in the working face.

Claims

1. A method for pressure relief by large-diameter boreholes in the high-level stress area of regional structures, characterized in that, it includes the following steps: (1) Explore the stress state of the roadway side through the in-situ stress test method, determine the stress concentration state and distribution law of the roadway side, and obtain the direction of the maximum horizontal principal stress; (2) According to the direction of the maximum horizontal principal stress obtained in step (1), calculate the construction direction of the pressure relief boreholes, and the construction direction of the pressure relief boreholes is perpendicular to the direction of the maximum horizontal principal stress; (3) According to the geological conditions and stress environment factors in the area where the coal seam is located, and based on the construction direction of the pressure relief boreholes determined in step (2), determine the construction parameters of the pressure relief boreholes. The construction parameters of the pressure relief boreholes include the depth of the pressure relief boreholes, the diameter of the pressure relief boreholes, the spacing of the pressure relief boreholes, and the layout method of the pressure relief boreholes; for the spacing of the pressure relief boreholes in the high-level stress area, it is also necessary to determine according to the impact hazard level; The construction requirement for the depth of the pressure relief boreholes to meet the minimum impact hazard index is as follows: The attenuation of energy is in a power relationship with the propagation distance. For simplified analysis, without considering the difference in energy attenuation, the calculation formula for the impact hazard index after borehole pressure relief is obtained as follows: Where a 1 is the area of high stress area 1, with the unit of m 2 ; l 1 is the distance between the center of high stress area 1 and the roadway side; a 2 is the area of high stress area 2, with the unit of m 2 ; l 2 is the distance between the center of high stress area 2 and the roadway side, with the unit of m; when the relief borehole satisfies the minimum impact hazard index, the relief effect is the most obvious; The diameter of the pressure relief boreholes is taken as 110 mm; The construction requirement for the spacing of the pressure relief boreholes to meet the determination process of the weakening area formed around each borehole is as follows: When large-diameter borehole pressure relief is carried out in the high-level stress area, a stress reduction area is formed on one side of each borehole. After the stress reduction areas are connected to each other, a whole-penetrating coal body softening area is formed, which is the weakening area; The construction requirement for the layout method of the pressure relief boreholes to meet the superposition of the pressure relief circles and ensure the pressure relief range is as follows: Adopt a single-row borehole layout. A stress reduction area is formed around each single borehole, and the stress reduction areas around each borehole are connected to each other to form a larger stress reduction area.

2. A method for pressure relief by large-diameter boreholes in the high-level stress area of regional structures according to claim 1, characterized in that, in step (1), the direction of the maximum horizontal principal stress is measured by the in-situ stress measurement method of stress relief, and the measurement system adopts the hollow inclusion strain gauge method of the borehole wall deformation method. Specifically: 201) In the rock mass of the chamber or roadway, use a sleeve borehole or a cut groove to separate part of the rock sample from the surrounding rock, monitor and record the strain value of the rock sample through a strain gauge, and obtain the magnitude and direction of the in-situ stress at the measuring point according to the existing stress-strain relationship and the elastic modulus of the rock sample; 202) According to the magnitude and direction of the in-situ stress at the measuring point obtained in step 201), there are two principal stresses in the nearly horizontal direction at each measuring point, indicating that the horizontal tectonic stress dominates. Use the least squares linear fitting to perform a regression analysis on the stress values of each measuring point, and obtain the fitting formula of the maximum horizontal principal stress at the measuring point and the buried depth of the measuring point as follows: σ h,max = mH + n; Among them, σ h,max is the maximum horizontal principal stress of the measurement point; H is the buried depth of the measurement point; m and n are constants, and the unique values are obtained by fitting a straight line through the least squares method.

3. A method for pressure relief by large-diameter boreholes in the high-level stress area of regional structures according to claim 2, characterized in that, in step (2), in the high-level stress area, let the angle between the maximum horizontal principal stress and the axial direction of the roadway be α, then the calculation formula for determining the angle between the construction direction of the pressure relief boreholes and the axial direction of the roadway is: γ = α + 90°.

4. A method for pressure relief by large-diameter boreholes in the high-level stress area of regional structures according to claim 3, characterized in that, In the said step (3), the impact danger levels are classified into a weak impact danger area, a medium impact danger area and a strong impact danger area through impact danger assessment.

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