A coal body blasting and large-diameter drilling cooperative pressure relief method in high stress area of steep coal seam

Abstract

A kind of coal body blasting and large-diameter drilling collaborative pressure relief method in high stress area of steep coal seam, steps include: obtaining mine geological survey data and ground stress test data, determining high stress area roadway construction area according to comprehensive index method, drill cuttings method, stress monitoring method;Multiple blasting holes are arranged along the trend of roadway in the high stress area roadway side, and coal body blasting is carried out;After coal body blasting is completed, large-diameter drilling is arranged in the same roadway side;The construction area is evaluated for pressure relief effect, and if the pressure relief effect evaluation reaches the set standard, the construction is completed, otherwise, the drilling density is increased until the pressure relief effect reaches the set standard.The present application can improve the construction depth of large-diameter drilling in high stress area of steep coal seam, make coal body blasting and large-diameter drilling collaborative pressure relief form effective pressure relief zone, reduce the stress concentration degree of the area, and further reduce the risk of rock burst in roadway.

Description

Technical Field

[0001] This invention relates to a method for synergistic pressure relief through coal body blasting and large-diameter drilling in the high-stress zone of steeply inclined coal seams, belonging to the field of coal mine rockburst prevention technology. Background Technology

[0002] Rockbursts are a common dynamic disaster in coal mining. With the increase in mining depth and intensity, especially in the deep mining stage, the risk of rockburst disasters under high ground stress and strong mining activity is becoming increasingly prominent. Large-diameter borehole stress relief technology is widely used for stress relief in roadway surrounding rock and coal seam due to its simple construction and direct effect. However, conventional large-diameter borehole construction is extremely difficult in the high-stress zone of steeply inclined coal seams. Drill rod jamming and drill bit sticking occur frequently, and the drilling depth is severely limited, often failing to reach the designed stress relief depth, resulting in a significant reduction in stress relief effect. Although coal seam blasting alone can release some stress, without the continuous guidance of subsequent boreholes, the stress is prone to re-concentration, and the stress relief effect is not lasting.

[0003] Therefore, how to increase the construction depth of large-diameter boreholes in roadways in steeply inclined coal seams with high stress zones, so that coal blasting and large-diameter boreholes can work together to relieve pressure and form an effective pressure relief zone, thereby reducing the stress concentration in the area and thus reducing the risk of rockbursts in the roadways, is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a method for stress relief through coal blasting and large-diameter drilling in the high-stress zone of steeply inclined coal seams. This method can effectively reduce the stress concentration in the high-stress zone of steeply inclined coal seams and reduce the risk of rockbursts in roadways.

[0005] To achieve the above objectives, the present invention provides a method for coordinating pressure relief through coal body blasting and large-diameter drilling in the high-stress zone of steeply inclined coal seams, comprising the following steps:

[0006] S1. Obtain mine geological survey data and geostress test data, and determine the construction area of ​​roadway in high-stress zone based on comprehensive index method, drill cuttings method and stress monitoring method;

[0007] S2. In the sidewalls of the roadway in the high-stress zone, multiple blasting holes are arranged along the roadway direction, and coal blasting is carried out.

[0008] S3. After the coal body blasting is completed, large-diameter boreholes are arranged on the sidewall of the same roadway;

[0009] S4. Evaluate the pressure relief effect in the construction area. If the pressure relief effect meets the set standard, the construction is completed; otherwise, increase the drilling density until the pressure relief effect meets the set standard.

[0010] Furthermore, in the S2 section, the coal seam blasting holes are constructed sequentially at intervals of 6-10m. The diameter of the blasting holes is 42-100mm, and the hole depth is not less than the distance from the coal wall of the roadway to the stress concentration peak point. The holes are arranged perpendicular to the roadway sidewalls, and the hole height is 1.0-1.5m above the roadway floor. The charge length does not exceed half of the drilling depth, and the sealing length is not less than 1 / 3 of the hole depth.

[0011] Coal blasting shall use permitted explosives with a safety level of not less than level II for coal mines, and the sealing material shall be water-based gunning mud, clay gunning mud, or other non-combustible, plastic loose materials.

[0012] Furthermore, in the S3 section, after the blasting holes are completed, the large-diameter borehole pressure relief is carried out in sequence along the roadway with a spacing of 1-3m, a depth of not less than 25m, a diameter of more than 100mm, and an inclination angle of 15-30°, starting and ending 3m before and after the coal blasting area.

[0013] Specifically, when the rockburst risk level is weak, the spacing between large-diameter boreholes is 3m; when the rockburst risk level is medium, the spacing between large-diameter boreholes is 2m; and when the rockburst risk level is strong, the spacing between large-diameter boreholes is 1m.

[0014] Furthermore, the method for evaluating the pressure relief effect in the construction area during step S4 is as follows:

[0015] After the coordinated depressurization is completed, the effect of depressurization in the high-stress area of ​​the steeply inclined coal seam is tested using microseismic monitoring, stress monitoring, and drill cuttings monitoring. If all early warning indicators are lower than before depressurization, that is, the set standard is met, it indicates that the depressurization effect is good and the depressurization is completed. Otherwise, it indicates that the coal seam still has the risk of rockburst, and measures such as increasing the density of large-diameter boreholes are needed to reduce the risk of rockburst until the depressurization effect test meets the set standard.

[0016] This invention utilizes coal blasting in high-stress areas of steeply inclined coal seams. The resulting coal fractures effectively release localized high stress, improving the success rate and efficiency of subsequent large-diameter drilling. Through a cyclical pattern of "blasting-drilling-re-blasting-re-drilling," the loosened area from blasting and the stress-relief area from drilling spatially overlap and connect, eliminating stress-relief gaps. The combined stress relief from coal blasting and large-diameter drilling creates an effective stress-relief zone, significantly reducing the risk of rockbursts in high-stress areas, thereby lowering the risk of rockbursts in the roadways. This has significant practical implications for the prevention and control of rockburst risks in coal mines. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the workflow of the method of the present invention;

[0018] Figure 2This is a schematic diagram of the coordinated pressure relief of coal body blasting and large-diameter drilling in an embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of the cross-section of coal body blasting and large-diameter borehole pressure relief in an embodiment of the present invention.

[0020] In the diagram: 1. Roadway sidewall, 2. Coal blasting hole, 3. Roadway, 4. Large-diameter borehole. Detailed Implementation

[0021] The invention will now be further described with reference to the accompanying drawings.

[0022] like Figure 1 As shown, a method for coordinating coal body blasting and large-diameter borehole drilling to relieve pressure in the high-stress zone of steeply inclined coal seams includes the following steps:

[0023] S1. Obtain mine geological survey data and geostress test data, and determine the construction area of ​​roadway in high-stress zone based on comprehensive index method, drill cuttings method and stress monitoring method;

[0024] S2. In the sidewalls of the roadway in the high-stress zone, multiple blasting holes are arranged along the roadway direction, and coal blasting is carried out.

[0025] S3. After the coal body blasting is completed, large-diameter boreholes are arranged on the sidewall of the same roadway;

[0026] S4. Evaluate the pressure relief effect in the construction area. If the pressure relief effect meets the set standard, the construction is completed; otherwise, increase the drilling density until the pressure relief effect meets the set standard.

[0027] Furthermore, in the S2 section, the coal seam blasting holes are constructed sequentially at intervals of 6-10m. The diameter of the blasting holes is 42-100mm, and the hole depth is not less than the distance from the coal wall of the roadway to the stress concentration peak point. The holes are arranged perpendicular to the roadway sidewalls, and the hole height is 1.0-1.5m above the roadway floor. The charge length does not exceed half of the drilling depth, and the sealing length is not less than 1 / 3 of the hole depth.

[0028] Coal blasting shall use permitted explosives with a safety level of not less than level II for coal mines, and the sealing material shall be water-based gunning mud, clay gunning mud, or other non-combustible, plastic loose materials.

[0029] Furthermore, in the S3 section, after the blasting holes are completed, the large-diameter borehole pressure relief is carried out in sequence along the roadway with a spacing of 1-3m, a depth of not less than 25m, a diameter of more than 100mm, and an inclination angle of 15-30°, starting and ending 3m before and after the coal blasting area.

[0030] Specifically, when the rockburst risk level is weak, the spacing between large-diameter boreholes is 3m; when the rockburst risk level is medium, the spacing between large-diameter boreholes is 2m; and when the rockburst risk level is strong, the spacing between large-diameter boreholes is 1m.

[0031] Furthermore, the method for evaluating the pressure relief effect in the construction area during step S4 is as follows:

[0032] After the coordinated depressurization is completed, the effect of depressurization in the high-stress area of ​​the steeply inclined coal seam is tested using microseismic monitoring, stress monitoring, and drill cuttings monitoring. If all early warning indicators are lower than before depressurization, that is, the set standard is met, it indicates that the depressurization effect is good and the depressurization is completed. Otherwise, it indicates that the coal seam still has the risk of rockburst, and measures such as increasing the density of large-diameter boreholes are needed to reduce the risk of rockburst until the depressurization effect test meets the set standard.

[0033] Example: Taking the lower roadway of the 1503 working face in a steeply inclined coal mine as an example, due to the presence of a syncline structure in the middle of the roadway, it is impossible to reach the designed depth when drilling large-diameter boreholes. Based on the high-stress zone environment of the steeply inclined coal seam where the roadway is located, this invention is used to coordinate coal blasting and large-diameter borehole decompression. The specific implementation steps are as follows:

[0034] Geological survey data of the mine was obtained. Based on the comprehensive index method, drill cuttings method, stress monitoring method and other methods, it was found that the stress in the middle of the roadway of the 1503 working face was relatively high. Coordinated pressure relief was carried out in the sidewall of the roadway.

[0035] like Figure 2 Figures and Figure 3 As shown, coal blasting holes are arranged on the lower sidewall of the 1503 working face. Coal blasting holes 2 are constructed sequentially along the direction of roadway 3 at 6m intervals. The parameters of a single coal blasting hole 2 are as follows: hole diameter 42mm, hole depth 13m, arranged perpendicular to the roadway sidewall, hole height 1.0m above the roadway floor; charge length 6m, sealing length 7m, and charge amount per hole 4.5kg.

[0036] After the coal body is blasted and depressurized, large-diameter boreholes 4 are arranged in the sidewall 1 of the roadway, starting 3m before and after the blasting area. The area is assessed as having a medium impact risk. The large-diameter boreholes 4 are spaced 2m apart, with a diameter of 133mm and a depth of 25m or until rock is encountered. The height of the boreholes is 1.5m above the roadway floor. According to the ground stress test, the direction of the maximum principal stress is perpendicular to the roadway. To ensure the depressurization effect of the large-diameter boreholes, the borehole direction is at a 20° angle to the direction perpendicular to the roadway sidewall, and the borehole inclination angle is 30°.

[0037] After the coal seam blasting and large-diameter borehole pressure relief were completed, the pressure relief effect was tested in the construction area. Microseismic monitoring results showed that no microseismic events of magnitude 4 or higher occurred during subsequent mining operations after pressure relief, and the daily frequency of microseismic events decreased from an average of 60 times per day before pressure relief to 40 times per day. Drill cuttings monitoring results showed that the amount of coal dust extracted decreased from 2.85 kg / m³ before pressure relief to 2.44 kg / m³. Stress monitoring results showed that the stress value at shallow measuring points decreased from 11.5 MPa before pressure relief to 10.5 MPa, and the stress value at deep measuring points decreased from 13.8 MPa before pressure relief to 12.2 MPa. The test results showed that all warning indicators were lower than before pressure relief, indicating that the pressure relief effect was good and the pressure relief was successfully completed.

Claims

1. A method for coordinating coal body blasting and large-diameter drilling to relieve pressure in the high-stress zone of steeply inclined coal seams, characterized in that, Includes the following steps: S1. Obtain mine geological survey data and geostress test data, and determine the construction area of ​​roadway in high-stress zone based on comprehensive index method, drill cuttings method and stress monitoring method; S2. In the sidewalls of the roadway in the high-stress zone, multiple blasting holes are arranged along the roadway direction, and coal blasting is carried out. S3. After the coal body blasting is completed, large-diameter boreholes are arranged on the sidewall of the same roadway; S4. Evaluate the pressure relief effect in the construction area. If the pressure relief effect meets the set standard, the construction is completed; otherwise, increase the drilling density until the pressure relief effect meets the set standard.

2. The method for coordinated pressure relief through coal body blasting and large-diameter drilling in the high-stress zone of steeply inclined coal seams according to claim 1, characterized in that, The coal blasting holes in S2 are constructed sequentially at intervals of 6-10m. The diameter of the blasting holes is 42-100mm, and the hole depth is not less than the distance from the coal wall of the roadway to the stress concentration peak point. They are arranged perpendicular to the roadway sidewall, and the hole height is 1.0-1.5m above the roadway floor. The charge length does not exceed half of the drilling depth, and the sealing length is not less than 1 / 3 of the hole depth. Coal blasting shall use permitted explosives with a safety level of not less than level II for coal mines, and the sealing material shall be water-based gunning mud, clay gunning mud, or other non-combustible, plastic loose materials.

3. The method for coordinated pressure relief through coal body blasting and large-diameter drilling in the high-stress zone of steeply inclined coal seams according to claim 1, characterized in that, After the blasting holes are completed, the large-diameter borehole pressure relief in S3 is carried out in sequence with a starting point of 3m before and after the coal blasting area. According to the evaluated impact hazard level, the large-diameter boreholes are constructed along the roadway with a spacing of 1-3m, a depth of not less than 25m, a diameter of more than 100mm, and an inclination angle of 15-30°. Specifically, when the rockburst risk level is weak, the spacing between large-diameter boreholes is 3m; when the rockburst risk level is medium, the spacing between large-diameter boreholes is 2m; and when the rockburst risk level is strong, the spacing between large-diameter boreholes is 1m.

4. The method for coordinated pressure relief through coal body blasting and large-diameter drilling in the high-stress zone of steeply inclined coal seams according to claim 1, characterized in that, The method for evaluating the pressure relief effect in the construction area in S4 is as follows: After the coordinated depressurization is completed, the effect of depressurization in the high-stress area of ​​the steeply inclined coal seam is tested using microseismic monitoring, stress monitoring, and drill cuttings monitoring. If all early warning indicators are lower than before depressurization, that is, the set standard is met, it indicates that the depressurization effect is good and the depressurization is completed. Otherwise, it indicates that the coal seam still has the risk of rockburst, and measures such as increasing the density of large-diameter boreholes are needed to reduce the risk of rockburst until the depressurization effect test meets the set standard.

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