A method for controlling rock burst in hard roof of coal mine tunnel

Abstract

The present invention discloses a method for controlling rock burst in a hard roof of a coal mine tunnel, the method comprising the following steps: 1. determining the position of a region to be unloaded; 2. collecting the original apparent resistivity of the region to be unloaded before unloading; 3. unloading the region to be unloaded; 4. measuring the average development height of internal cracks in the region to be unloaded after unloading; 5. judging the level of danger of unloading impact in the region to be unloaded; 6. adjusting the aperture of the unloading borehole in the region to be unloaded and unloading the pressure again; 7. supplementary unloading of the region to be unloaded; 8. completing unloading of the region to be unloaded. The rock burst control method adopted by the present invention can perform high-pressure hydraulic fracturing in the region to be unloaded, and make the average development height of the cracks in the region to be unloaded cover the entire region to be unloaded, effectively fracturing and weakening the region to be unloaded, prompting the hard roof of the coal seam to collapse in time, effectively controlling the rock burst disaster caused by the hard roof of the coal seam, having a good control effect and being easy to promote and use.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mining face roof rock burst control, and in particular relates to a method for controlling rock burst of a hard roof of a coal mine tunnel. Background Art

[0002] In recent years, with the needs of economic development, the depth of coal resource mining has increased year by year, and rock burst disasters have become increasingly severe. It has become the most important disaster affecting the safe production of coal mines in my country, and seriously threatens the safety of underground personnel and equipment. Roof fracture type rock burst is a typical rock burst disaster. The mechanism of roof fracture type rock burst is: with the mining of the working face, the hard roof is not easy to collapse in time, resulting in a large amount of elastic energy accumulating in the roof. Once the roof is unstable and fractured, it will instantly release huge elastic energy, thereby inducing coal body rupture and generating outward projection movement, which eventually causes rock burst, causing vibration and destruction of coal and rock mass, damage to supports and equipment, casualties, collapse and destruction of some tunnels and other dynamic phenomena. Rock burst will also cause or may cause other mine disasters, especially gas and coal dust explosions, fires and floods, interfere with ventilation systems, and cause ground vibrations and building damage in severe cases. At present, the methods for dealing with the rock burst disaster of hard roof are mainly divided into two categories: passive protection and active weakening. Passive protection mainly adopts increasing anchor rods or anchor cable support, filling tunnels or working faces with special materials to support hard roof rock layers to avoid sudden collapse of hard roof, but it cannot fundamentally control the hard roof; active weakening mainly includes pre-splitting blasting and water injection softening. The pre-splitting blasting method can break and collapse the roof and eliminate stress concentration, but it has problems such as large engineering volume, high cost, large amount of gunpowder, high risk factor, and blasting produces toxic gases such as CO that pollute the underground environment. There are also safety hazards for high-gas or gas outburst mines; the water injection softening method is relatively safe in construction and can be operated in parallel underground with little impact on production, but it is not very effective for hard sandstone and has poor pressure relief effect.

[0003] Therefore, there is a lack of a method with simple steps and reasonable design for controlling rock burst in hard roof of coal mine tunnels to solve the problems of high risk factor and poor control effect in the existing control of rock burst in hard roof. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for controlling rock burst caused by the hard roof of a coal mine tunnel in response to the deficiencies in the above-mentioned prior art, to perform high-pressure hydraulic fracturing on the area to be unloaded, and to make the average development height of the cracks in the area to be unloaded cover the entire area to be unloaded, to effectively weaken the area to be unloaded by fracturing, to prompt the hard roof of the coal seam to collapse in time, to effectively control the rock burst disaster caused by the hard roof of the coal seam, to have a good control effect, and to facilitate popularization and use.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for controlling rock burst in a hard roof of a coal mine tunnel, characterized in that the method comprises the following steps:

[0006] Step 1: Determine the location of the area to be depressurized;

[0007] Step 2: collecting the original apparent resistivity of the area to be depressurized before depressurization;

[0008] Step 3, depressurizing the area to be depressurized;

[0009] Step 4: measuring the average development height of the internal cracks in the area to be depressurized after depressurization;

[0010] Step 5: Determine the pressure relief impact hazard level of the pressure relief area according to the average development height of the internal cracks in the pressure relief area after pressure relief;

[0011] Step 6: Adjust the diameter of the pressure relief borehole in the pressure relief area and perform pressure relief again;

[0012] Step 7: Supplementary pressure relief to the pressure relief area;

[0013] Step 8: Complete the pressure relief in the area to be relieved.

[0014] The above-mentioned method for controlling rock burst in a hard roof of a coal mine tunnel is characterized in that: in step 1, the position of the area to be relieved is determined, and the specific process is as follows:

[0015] Determine the stratum of the hard roof of the coal seam overlying the coal mining working face. The area where the hard roof of the coal seam is located in the vertical downward movement zone is the area to be depressurized.

[0016] The above-mentioned method for controlling rock burst in a hard roof of a coal mine tunnel is characterized in that: in step 2, the original apparent resistivity of the area to be depressurized before depressurization is collected, and the specific process is as follows:

[0017] Step 201: M groups of measuring points are arranged in sequence from back to front along the length direction of the coal mining face, each group of measuring points includes a first measuring point located in the transport tunnel and a second measuring point located in the return air tunnel; wherein M is a positive integer, and M≥3;

[0018] Step 202: measuring the apparent resistivity of the area to be depressurized at M groups of measuring points respectively, and obtaining a set of original apparent resistivity sequences of the M areas to be depressurized. The measuring methods of the apparent resistivity of the area to be depressurized at the M groups of measuring points are the same. When measuring the apparent resistivity of the area to be depressurized at the mth group of measuring points, the following steps are mainly included:

[0019] Step 2021, placing a transient electromagnetic instrument at the first measuring point of the mth group of measuring points, so that the plane where the transmitting coil of the transient electromagnetic instrument is located is parallel to the vertical plane where the central axis of the transport lane is located, and then rotating the transmitting coil of the transient electromagnetic instrument by 90° clockwise. During the rotation of the transmitting coil of the transient electromagnetic instrument, the transient electromagnetic instrument measures the apparent resistivity of the area to be depressurized according to the set measuring interval, and obtains the original apparent resistivity of the area to be depressurized at different angles at the first measuring point of the mth group of measuring points; wherein m is the measuring point number, 1≤m≤M, and the measuring interval is 10°-15°;

[0020] Step 2022, placing the transient electromagnetic instrument at the second measuring point of the mth group of measuring points, so that the plane where the transmitting coil of the transient electromagnetic instrument is located is parallel to the vertical plane where the central axis of the return air tunnel is located, and then rotating the transmitting coil of the transient electromagnetic instrument counterclockwise by 90°. During the rotation of the transmitting coil of the transient electromagnetic instrument, the transient electromagnetic instrument measures the apparent resistivity of the area to be depressurized according to the set measurement interval, and obtains the original apparent resistivity of the area to be depressurized at different angles at the second measuring point of the mth group of measuring points;

[0021] Step 2023: Arrange the original apparent resistivity of the area to be depressurized at different angles at the first measuring point of the mth group of measuring points obtained in step 2021 and the original apparent resistivity of the area to be depressurized at different angles at the second measuring point of the mth group of measuring points obtained in step 2022 in the order of measurement time to obtain the original apparent resistivity sequence set ρ of the area to be depressurized at the mth group of measuring points 0m , the original apparent resistivity series set ρ 0m It includes A original apparent resistivity, and the original apparent resistivity sequence set ρ 0m The ath original apparent resistivity is denoted as ρ 0ma ; Where A is a positive integer, a is the original apparent resistivity number, 1≤a≤A.

[0022] The above-mentioned method for controlling rock burst in a hard roof of a coal mine tunnel is characterized in that: in step 3, the pressure is relieved in the area to be relieved, and the specific process is as follows:

[0023] Step 301: Determine the diameter d of the test borehole to be constructed in the area to be depressurized. 1 , a starting position and an end position, constructing a test borehole in the area to be depressurized, and performing hydraulic fracturing in the test borehole; wherein the test borehole is arranged close to the left end of the area to be depressurized, and the center of the test borehole is located on the horizontal center line of the area to be depressurized;

[0024] Step 302: According to the method described in step 202, the apparent resistivity of the area to be depressurized is measured again at the M groups of measuring points to obtain the first apparent resistivity sequence set of the M areas to be depressurized; wherein the apparent resistivity of the area to be depressurized at the m-th group of measuring points is measured to obtain the first apparent resistivity sequence set ρ of the area to be depressurized at the m-th group of measuring points 1m , the first apparent resistivity sequence set ρ 1m A first apparent resistivity sequence set ρ 1m The ath first apparent resistivity is denoted as ρ 1ma ;

[0025] Step 303: Process the first apparent resistivity sequence set and the original apparent resistivity sequence set at the M group of measuring points to obtain the effective fracturing width and effective fracturing height of the test borehole at the M group of measuring points. The method for processing the first apparent resistivity sequence set and the original apparent resistivity sequence set at the M group of measuring points is the same. The first apparent resistivity sequence set ρ at the mth group of measuring points is processed. 1m and the original apparent resistivity series set ρ 0m The data processing mainly includes the following steps:

[0026] Step 3031: For the first apparent resistivity sequence set ρ 1m The A first apparent resistivity and original apparent resistivity series set ρ 0m The A original apparent resistivities in the mth group are matched one by one, and the decrease of the A first apparent resistivities at the mth group of measuring points is calculated respectively; among them, the calculation method of the decrease of the A first apparent resistivities is the same. When calculating the decrease of the ath first apparent resistivity, the formula is used. The decrease J of the ath first apparent resistivity is calculated 1a ;

[0027] Step 3032: According to the A first apparent resistivity drop amplitudes and the first apparent resistivity sequence set ρ 1m The effective fracturing area of ​​the test borehole at the mth group of measuring points is determined by the A first apparent resistivity in the test borehole; wherein, the division basis of the effective fracturing area of ​​the test borehole is: when the ath first apparent resistivity ρ 1ma ≤35Ω·m, and the ath first apparent resistivity ρ 1ma The decline in 1a When ≥50%, the area corresponding to the ath first apparent resistivity is located within the effective fracturing area of ​​the test borehole;

[0028] Step 3033: measure the average width of the effective fracturing area of ​​the test borehole at the mth group of measuring points as the effective fracturing width b of the test borehole at the mth group of measuring points. 1m, measure the average height of the effective fracturing area of ​​the test borehole at the mth group of measuring points as the effective fracturing height h of the test borehole at the mth group of measuring points 1m ;

[0029] Step 304: According to the formula Calculate the average effective fracturing height of the test boreholes in the area to be depressurized

[0030] According to the formula Calculate the average effective fracture width of the test boreholes in the area to be depressurized

[0031] when When , execute step 305, when When , execute step 306; wherein, H 1 is the maximum height of the area to be depressurized;

[0032] Step 305: construct N rows of pressure relief boreholes along the length direction of the area to be relieved, each row of pressure relief boreholes includes one pressure relief borehole, and perform hydraulic fracturing in the N pressure relief boreholes to complete the pressure relief of the area to be relieved; wherein, Indicates rounding up, B 1 is the maximum width of the area to be depressurized. The structure of the depressurization borehole is the same as that of the test borehole. The centers of the multiple depressurization boreholes and the test boreholes are located on the same straight line. The hole spacing between two adjacent rows of depressurization boreholes is k. 1 ,

[0033] Step 306: construct N rows of pressure relief boreholes along the length direction of the area to be relieved, each row of pressure relief boreholes includes two pressure relief boreholes, and hydraulic fracturing is performed in the 2N pressure relief boreholes to complete the pressure relief of the area to be relieved; wherein the two pressure relief boreholes in each row of pressure relief boreholes are located at the upper and lower sides of the test borehole, respectively, and the hole spacing between the two pressure relief boreholes in each row of pressure relief boreholes is k 2 ,

[0034] The above-mentioned method for controlling rock burst in a hard roof of a coal mine tunnel is characterized in that: in step 4, the average development height of the internal cracks in the area to be unloaded after unloading is measured, and the specific process is as follows:

[0035] Step 401: According to the method described in step 302, the apparent resistivity of the area to be depressurized is measured again at M groups of measuring points to obtain a second apparent resistivity sequence set of M areas to be depressurized; wherein, the apparent resistivity of the area to be depressurized at the mth group of measuring points is measured to obtain a second apparent resistivity sequence set ρ of the area to be depressurized at the mth group of measuring points 2m , the second apparent resistivity series set ρ2m A second apparent resistivity sequence set ρ 2m The ath second apparent resistivity is denoted as ρ 2ma ;

[0036] Step 402: According to the method described in step 303, the second apparent resistivity sequence set and the original apparent resistivity sequence set at the M groups of measuring points are processed to obtain the effective fracturing area and effective fracturing height of the N columns of pressure relief boreholes at the M groups of measuring points; wherein the effective fracturing height of the nth column of pressure relief boreholes at the mth group of measuring points is h 2mn , n is a positive integer, and 1≤n≤N;

[0037] Step 403: According to the formula Calculate the average effective fracturing height of N rows of pressure relief boreholes at the mth group of measuring points

[0038] Step 404: According to the formula Calculate the average fracturing height of N rows of decompression boreholes in the decompression area Then the average development height H of the internal cracks in the area to be unloaded after unloading is obtained. 2 ,

[0039] The above-mentioned method for controlling rock burst in a hard roof of a coal mine tunnel is characterized in that: in step 5, the pressure relief impact hazard level of the area to be relieved is judged according to the average development height of the internal cracks in the area to be relieved after pressure relief, and the specific process is as follows:

[0040] When 0.1H 1 ≤H 2 ≤0.8H 1 When the impact hazard level of the area to be depressurized is Level I, execute step 6;

[0041] When 0.8H 1 <H 2 <H 1 When the impact hazard level of the area to be depressurized is Level II, execute step 7;

[0042] When H 2 ≥H 1 When the impact hazard level of the area to be depressurized is level III, execute step eight;

[0043] The risk of the level I impact hazard is higher than that of the level II impact hazard, and the risk of the level II impact hazard is higher than that of the level III impact hazard.

[0044] The above-mentioned method for controlling rock burst in a hard roof of a coal mine tunnel is characterized in that: in step 6, the diameter of the pressure relief borehole in the pressure relief area to be relieved is adjusted and pressure relief is performed again, and the specific process is as follows:

[0045] The diameter d of the pressure relief hole in the pressure relief area 1 Increase Δd to obtain a pressure relief borehole with an increased aperture, perform hydraulic fracturing in the pressure relief borehole with an increased aperture, and regard the pressure relief borehole with an increased aperture as a pressure relief borehole, and repeat step 4; wherein,

[0046] The above-mentioned method for controlling rock burst in a hard roof of a coal mine tunnel is characterized in that: in step seven, additional pressure relief is performed on the area to be relieved, and the specific process is as follows:

[0047] According to the effective fracturing area of ​​the N columns of pressure relief boreholes at the mth group of measuring points in step 402, the ineffective fracturing area at the mth group of measuring points after pressure relief is determined, and the ineffective fracturing area at the mth group of measuring points is regarded as the ineffective fracturing area of ​​the area to be relieved, the number of ineffective fracturing areas is Q, and the Q ineffective fracturing areas are all supplemented with pressure relief; wherein, the judgment basis of the ineffective fracturing area at the mth group of measuring points is: the area except the effective fracturing area of ​​the N columns of pressure relief boreholes in the area to be relieved at the mth group of measuring points is the ineffective fracturing area at the mth group of measuring points, Q is a positive integer, and Q≥1, the method of supplementing the pressure relief of the Q ineffective fracturing areas is the same, and when supplementing the pressure relief of the qth ineffective fracturing area, the following steps are mainly included:

[0048] Step 701: Measure the maximum width b of the qth ineffective fracturing area. 3max and the maximum height h 3max ;

[0049] Step 702: Determine the number of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area:

[0050] According to the formula The number of columns L of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is calculated.

[0051] According to the formula The number P of supplementary pressure relief boreholes in each column of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is calculated, and then the number of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is determined. The number of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is L×P; wherein, Indicates rounding up;

[0052] Step 703: construct L×P supplementary pressure relief boreholes in the qth ineffective fracturing area, and perform hydraulic fracturing in the L×P supplementary pressure relief boreholes to complete the supplementary pressure relief in the qth ineffective fracturing area; wherein the structure of the supplementary pressure relief borehole is the same as that of the test borehole, and the aperture of the supplementary pressure relief borehole is d 2 , d 2 =d 1 ;

[0053] Step 704: According to the method described in step 302, the apparent resistivity of the area to be depressurized is measured again at M groups of measuring points to obtain a third apparent resistivity sequence set of M areas to be depressurized;

[0054] Step 705: According to the method described in step 303, data processing is performed on the third apparent resistivity sequence set and the second apparent resistivity sequence set at the M groups of measuring points to obtain the effective fracturing area and effective fracturing height of the L columns of supplementary pressure relief boreholes at the M groups of measuring points; wherein the effective fracturing height of the lth column of pressure relief boreholes at the mth group of measuring points is h 3ml ; Wherein, l is a positive integer, and 1≤l≤L;

[0055] Step 706: According to the formula Calculate the average effective fracturing height of L rows of supplementary pressure relief boreholes at the mth group of measuring points

[0056] Step 707: According to the formula Calculate the average fracturing height of L rows of supplementary decompression boreholes in the area to be decompressed Then the average development height H of the internal cracks in the qth non-effective fracturing area after supplementary unloading is obtained: 3 ,

[0057] Step 708: Determine the average development height H of the internal cracks in the qth ineffective fracturing area after the supplementary unloading. 3 Is it less than the maximum height h of the qth ineffective fracturing area? 3max , if H 3 <h 3max , execute step 709; otherwise, execute step eight;

[0058] Step 709: Set the diameter d of the additional pressure relief borehole in the qth ineffective fracturing area. 2 Increase Δd to obtain a supplementary pressure relief borehole with an increased aperture, perform hydraulic fracturing in the supplementary pressure relief borehole with an increased aperture, and regard the supplementary pressure relief borehole with an increased aperture as a supplementary pressure relief borehole, and loop step 704.

[0059] The above-mentioned method for controlling rock burst in a hard roof of a coal mine tunnel is characterized in that: in step eight, pressure relief is completed in the area to be relieved, and the specific process is as follows:

[0060] Hydraulic fracturing is performed again in all depressurization boreholes to complete the depressurization of the area to be depressurized.

[0061] The above-mentioned method for controlling rock burst in a hard roof of a coal mine tunnel is characterized in that: the starting position and the ending position of the test borehole in step 301 are both located in front of the cut hole of the working face, the starting position of the test borehole is determined by the width of the coal mining working face, and the distance L between the starting position of the test borehole and the cut hole of the working face is 1 =2B 0 +L 0 , B 0 is the width of the coal mining face, L 0 To test the distance between the end position of the drill hole and the opening of the work surface, L 0 The value range is 20m~40m.

[0062] The beneficial effect of the present invention is that by determining the position of the area to be unloaded, the high-pressure hydraulic fracturing method is used to unload the area to be unloaded, and the apparent resistivity of the area to be unloaded before and after the unloading is measured respectively, and the average development height of the internal cracks in the area to be unloaded after the unloading is obtained according to the change of the apparent resistivity of the area to be unloaded before and after the unloading, and then the impact hazard level of the area to be unloaded is judged according to the average development height of the internal cracks in the area to be unloaded after the unloading, and when the impact hazard level of the area to be unloaded is greater than the impact hazard level required by the construction, the area to be unloaded is unloaded again or supplemented until the impact hazard level of the area to be unloaded is reduced. The level meets the impact hazard level required by the construction, completes the pressure relief in the area to be relieved, achieves full pressure relief in the area to be relieved, eliminates the risk of impact mine pressure caused by large-area suspended roof of the hard roof of the coal seam, avoids impact dynamic phenomena such as crushing of working face supports, hurricanes, and mine earthquakes during working face mining, effectively controls the impact ground pressure disasters caused by the hard roof, eliminates or reduces the suspended roof area of ​​the roof, and eliminates the risk of strong mine pressure in working face mining in advance. At the same time, the effective collapse of the hard roof of the entire coal seam reduces the rock pressure of the adjacent tunnels, which can simplify the tunnel support method, reduce production and maintenance costs, have good control effects, and are easy to promote and use.

[0063] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a flowchart of the method of the present invention.

[0065] Figure 2 This is a schematic diagram of the structure of Example 1 of the present invention.

[0066] Figure 3 This is a schematic diagram of the structure of Example 2 of the present invention.

[0067] Figure 4 It is a schematic diagram of the positional relationship of the area to be depressurized, the transport tunnel, the return air tunnel, the test borehole and the depressurization borehole of the present invention.

[0068] Description of reference numerals:

[0069] 1—coal mining face; 2—hard roof of coal seam; 3—vertical downward movement area;

[0070] 4—area to be depressurized; 4-1—depressurization section; 4-2—safety section;

[0071] 5—Transport tunnel; 6—Return air tunnel; 7—Transient electromagnetic instrument;

[0072] 8—test drilling hole; 9—pressure relief drilling hole; 10—first measuring point;

[0073] 11—The second measuring point. DETAILED DESCRIPTION

[0074] like Figures 1 to 4 As shown, the method for controlling rock burst in a hard roof of a coal mine tunnel according to the present invention comprises:

[0075] Step 1: Determine the location of the area to be depressurized;

[0076] Step 2: collecting the original apparent resistivity of the area to be depressurized before depressurization;

[0077] Step 3, depressurizing the area to be depressurized;

[0078] Step 4: measuring the average development height of the internal cracks in the area to be depressurized after depressurization;

[0079] Step 5: Determine the pressure relief impact hazard level of the pressure relief area according to the average development height of the internal cracks in the pressure relief area after pressure relief;

[0080] Step 6: Adjust the diameter of the pressure relief borehole in the pressure relief area and perform pressure relief again;

[0081] Step 7: Supplementary pressure relief to the pressure relief area;

[0082] Step 8: Complete the pressure relief in the area to be relieved.

[0083] The beneficial effect of the present invention is that by determining the position of the area 4 to be depressurized, the high-pressure hydraulic fracturing method is used to depressurize the area 4 to be depressurized, and the apparent resistivity of the area 4 to be depressurized before and after the depressurization is measured respectively, and the average development height of the internal cracks in the area to be depressurized after the depressurization is obtained according to the change of the apparent resistivity of the area 4 to be depressurized before and after the depressurization, and then the impact hazard level of the area to be depressurized 4 is judged according to the average development height of the internal cracks in the area to be depressurized after the depressurization, and when the impact hazard level of the area to be depressurized 4 is greater than the impact hazard level required by the construction, the area to be depressurized 4 is depressurized again or supplemented until the impact hazard level of the area to be depressurized is The hazard level meets the impact hazard level required by the construction, completes the depressurization of the area to be depressurized, achieves full depressurization in the area to be depressurized, eliminates the risk of impact mine pressure caused by large-area suspended roof of the hard roof of the coal seam, avoids impact dynamic phenomena such as crushing of working face supports, hurricanes, and mine earthquakes during working face mining, effectively controls the impact ground pressure disasters caused by the hard roof, eliminates or reduces the suspended roof area of ​​the roof, and eliminates the risk of strong mine pressure during working face mining in advance. At the same time, the effective collapse of the hard roof 2 of the entire coal seam reduces the rock pressure of the adjacent tunnel, which can simplify the tunnel support method, reduce production and maintenance costs, and has good control effects, which is easy to promote and use.

[0084] The rock burst control method adopted by the present invention can perform high-pressure hydraulic fracturing in the pressure relief area 4, and make the average development height of the cracks in the pressure relief area cover the entire pressure relief area 4, effectively fracturing and weakening the pressure relief area 4, prompting the hard roof of the coal seam to collapse in time, and effectively controlling the rock burst disaster caused by the hard roof 2 of the coal seam, with good control effect and easy to promote and use.

[0085] like Figure 2 and Figure 3 As shown, in this embodiment, the position of the area to be depressurized is determined in step 1, and the specific process is as follows:

[0086] The layer position of the hard roof 2 of the coal seam overlying the coal mining working face 1 is determined, and the area where the hard roof 2 of the coal seam is located in the vertical downward movement area 3 is the area 4 to be depressurized.

[0087] In the present embodiment, it should be noted that when determining the position of the area 4 to be unloaded, the position of the vertical downward movement zone 3 in the five overlying rock zones is first determined, and then the specific position of the area to be unloaded is determined according to the stratigraphic position of the hard roof 2 of the coal seam. The rock strata in the vertical downward movement zone 3 move perpendicularly to the ore layer under the action of gravity. The overlying rock in the vertical downward movement zone 3 is more prone to bending and deformation, and is more prone to weakening and cracking than the overlying rock in other areas. Therefore, the area with the hard roof 2 of the coal seam located in the vertical downward movement zone 3 is selected as the area 4 to be unloaded, so as to ensure the unloading effect of the hard roof 2 of the coal seam, and at the same time, can effectively reduce the unloading workload of the hard roof 2 of the coal seam.

[0088] In this embodiment, in actual use, the maximum width of the area to be relieved 4 is used as the overall width of the area to be relieved 4, so that the area to be relieved 4 has a rectangular structure, which is convenient for ensuring the pressure relief effect of the area to be relieved 4.

[0089] like Figure 3 and Figure 4 As shown, in this embodiment, in step 2, the original apparent resistivity of the area to be depressurized before depressurization is collected, and the specific process is as follows:

[0090] Step 201, M groups of measuring points are arranged in sequence from back to front along the length direction of the coal mining working face 1, each group of measuring points includes a first measuring point 10 located in the transport tunnel 5 and a second measuring point 11 located in the return air tunnel 6; wherein M is a positive integer, and M≥3;

[0091] Step 202, measuring the apparent resistivity of the area 4 to be depressurized at M groups of measuring points respectively, and obtaining a set of original apparent resistivity sequences of the M areas 4 to be depressurized. The measuring methods of the apparent resistivity of the area 4 to be depressurized at the M groups of measuring points are the same. When measuring the apparent resistivity of the area 4 to be depressurized at the mth group of measuring points, the following steps are mainly included:

[0092] Step 2021, placing the transient electromagnetic instrument 7 at the first measuring point 10 of the m-th group of measuring points, so that the plane where the transmitting coil of the transient electromagnetic instrument 7 is located is parallel to the vertical plane where the central axis of the transport tunnel 5 is located, and then rotating the transmitting coil of the transient electromagnetic instrument 7 90° clockwise. During the rotation of the transmitting coil of the transient electromagnetic instrument 7, the transient electromagnetic instrument 7 measures the apparent resistivity of the area to be depressurized 4 according to the set measuring interval, and obtains the original apparent resistivity of the area to be depressurized 4 at different angles at the first measuring point 10 of the m-th group of measuring points; wherein m is the measuring point number, 1≤m≤M, and the measuring interval is 10°~15°;

[0093] Step 2022, placing the transient electromagnetic instrument 7 at the second measuring point 11 of the m-th group of measuring points, so that the plane where the transmitting coil of the transient electromagnetic instrument 7 is located is parallel to the vertical plane where the central axis of the return air tunnel 6 is located, and then rotating the transmitting coil of the transient electromagnetic instrument 7 counterclockwise by 90°. During the rotation of the transmitting coil of the transient electromagnetic instrument 7, the transient electromagnetic instrument 7 measures the apparent resistivity of the area to be depressurized 4 according to the set measurement interval, and obtains the original apparent resistivity of the area to be depressurized 4 at different angles at the second measuring point 11 of the m-th group of measuring points;

[0094] Step 2023: Arrange the original apparent resistivity of the area 4 to be depressurized at different angles at the first measuring point 10 of the mth group of measuring points obtained in step 2021 and the original apparent resistivity of the area 4 to be depressurized at different angles at the second measuring point 11 of the mth group of measuring points obtained in step 2022 in the order of measurement time to obtain the original apparent resistivity sequence set ρ of the area 4 to be depressurized at the mth group of measuring points. 0m , the original apparent resistivity series set ρ 0m It includes A original apparent resistivity, and the original apparent resistivity sequence set ρ 0m The ath original apparent resistivity is denoted as ρ 0ma ; Where A is a positive integer, a is the original apparent resistivity number, 1≤a≤A.

[0095] In the present embodiment, it should be noted that when the transient electromagnetic instrument 7 is used to measure the apparent resistivity of the pressure relief area 4, a high-power transient electromagnetic instrument 7 is placed in the transport tunnel 5 or the return air tunnel 6 according to the principle of electromagnetic induction. The sudden change of the large current of the transient electromagnetic instrument 7 excites the transient electromagnetic field. The low-frequency part of these transient electromagnetic fields can effectively enter the rock formation where the pressure relief area 4 is located, and excite a secondary induced electromotive force in the rock formation where the pressure relief area 4 is located. The secondary induced electromotive force is related to the conductivity of the rock formation where the pressure relief area 4 is located. The secondary induced electromotive force can effectively pass through the rock formation and enter the receiving coil of the transient electromagnetic instrument 7 again. The apparent resistivity of the rock formation where the pressure relief area 4 is located is obtained by measuring the secondary induced electromotive force. The measurement is convenient, and no other drilling construction is required in the coal mine tunnel, which saves time and effort, and has high measurement accuracy, which is convenient for popularization and use.

[0096] In step 201, M groups of measuring points are arranged in sequence from back to front along the length direction of the area to be depressurized 4, the first group of measuring points in the M groups of measuring points and the end position of the test borehole 8 in the area to be depressurized 4 are located on the same vertical plane, and the last group of measuring points in the M groups of measuring points and the starting position of the test borehole 8 in the area to be depressurized 4 are located on the same vertical plane; each group of measuring points includes a first measuring point 10 and a second measuring point 11, and by measuring the apparent resistivity of the area to be depressurized 4 around the group of measuring points at the first measuring point 10 and the second measuring point 11 respectively, the apparent resistivity of the area to be depressurized 4 in a segment around the group of measuring points can be measured in all directions, and the measurement range is wide and the measurement accuracy is high;

[0097] By measuring the apparent resistivity of the area 4 to be depressurized at the M group of measuring points respectively, it is convenient to evaluate the overall depressurization effect of the area 4 to be depressurized later, and the evaluation accuracy is high;

[0098] In step 202, when measuring the apparent resistivity of the area to be depressurized 4 at each measuring point, the transient electromagnetic instrument 7 needs to be rotated to ensure that the measurement range of the transient electromagnetic instrument 7 covers the entire area to be depressurized 4, thereby improving the evaluation accuracy.

[0099] In this embodiment, in step 2021, when the transmitting coil of the transient electromagnetic instrument 7 rotates 90° clockwise, the transient electromagnetic instrument 7 rotates with its bottom edge as the center; in step 2022, when the transmitting coil of the transient electromagnetic instrument 7 rotates 90° counterclockwise, the transient electromagnetic instrument 7 rotates with its bottom edge as the center.

[0100] like Figure 2 , Figure 3 and Figure 4 As shown, in this embodiment, in step three, the pressure is released in the area to be released, and the specific process is as follows:

[0101] Step 301: Determine the diameter d of the test borehole 8 to be constructed in the pressure relief area 4. 1 , a starting position and an end position, constructing a test borehole 8 in the area to be depressurized 4, and performing hydraulic fracturing in the test borehole 8; wherein the test borehole 8 is arranged close to the left end of the area to be depressurized 4, and the center of the test borehole 8 is located on the horizontal center line of the area to be depressurized 4;

[0102] Step 302: According to the method described in step 202, the apparent resistivity of the area to be depressurized 4 is measured again at the M groups of measuring points to obtain the first apparent resistivity sequence set of the M areas to be depressurized 4; wherein the apparent resistivity of the area to be depressurized 4 at the m-th group of measuring points is measured to obtain the first apparent resistivity sequence set ρ of the area to be depressurized 4 at the m-th group of measuring points 1m , the first apparent resistivity sequence set ρ 1m A first apparent resistivity sequence set ρ 1m The ath first apparent resistivity is denoted as ρ 1ma ;

[0103] Step 303: Process the first apparent resistivity sequence set and the original apparent resistivity sequence set at the M group of measuring points to obtain the effective fracturing width and effective fracturing height of the test borehole 8 at the M group of measuring points. The method for processing the first apparent resistivity sequence set and the original apparent resistivity sequence set at the M group of measuring points is the same. The first apparent resistivity sequence set ρ at the mth group of measuring points is processed. 1m and the original apparent resistivity series set ρ 0m The data processing mainly includes the following steps:

[0104] Step 3031: For the first apparent resistivity sequence set ρ 1m The A first apparent resistivity and original apparent resistivity series set ρ0m The A original apparent resistivities in the mth group are matched one by one, and the decrease of the A first apparent resistivities at the mth group of measuring points is calculated respectively; among them, the calculation method of the decrease of the A first apparent resistivities is the same. When calculating the decrease of the ath first apparent resistivity, the formula is used. The decrease J of the ath first apparent resistivity is calculated 1a ;

[0105] Step 3032: According to the A first apparent resistivity drop amplitudes and the first apparent resistivity sequence set ρ 1m The effective fracturing area of ​​the test borehole 8 at the mth group of measuring points is determined by the A first apparent resistivity in the test borehole 8; wherein the division basis of the effective fracturing area of ​​the test borehole 8 is: when the ath first apparent resistivity ρ 1ma ≤35Ω·m, and the ath first apparent resistivity ρ 1ma The decline in 1a ≥50%, the area corresponding to the ath first apparent resistivity is located within the effective fracturing area of ​​the test borehole 8;

[0106] Step 3033: measure the average width of the effective fracturing area of ​​the test borehole 8 at the mth group of measuring points as the effective fracturing width b of the test borehole 8 at the mth group of measuring points. 1m , measure the average height of the effective fracturing area of ​​the test borehole 8 at the mth group of measuring points as the effective fracturing height h of the test borehole 8 at the mth group of measuring points 1m ;

[0107] Step 304: According to the formula Calculate the average effective fracturing height of the test borehole 8 in the area 4 to be depressurized

[0108] According to the formula Calculate the average effective fracturing width of the test borehole 8 in the area 4 to be depressurized

[0109] when When , execute step 305, when When , execute step 306; wherein, H 1 is the maximum height of the area to be depressurized 4;

[0110] Step 305: construct N rows of pressure relief boreholes along the length direction of the pressure relief area 4, each row of pressure relief boreholes includes a pressure relief borehole 9, and perform hydraulic fracturing in the N pressure relief boreholes 9 to complete the pressure relief of the pressure relief area 4; wherein, Indicates rounding up, B 1is the maximum width of the pressure relief area 4, the structure of the pressure relief borehole 9 is the same as that of the test borehole 8, the centers of the multiple pressure relief boreholes 9 and the centers of the test boreholes 8 are located on the same straight line, and the hole spacing between two adjacent rows of pressure relief boreholes is k 1 ,

[0111] Step 306: construct N rows of pressure relief boreholes along the length direction of the pressure relief area 4, each row of pressure relief boreholes includes two pressure relief boreholes 9, and perform hydraulic fracturing in the 2N pressure relief boreholes 9 to complete the pressure relief of the pressure relief area 4; wherein the two pressure relief boreholes 9 in each row of pressure relief boreholes 9 are located at the upper and lower sides of the test borehole 8, respectively, and the hole spacing between the two pressure relief boreholes 9 in each row of pressure relief boreholes is k. 2 ,

[0112] In this embodiment, in actual use, in step 3, a test borehole 8 is constructed in the pressure relief area 4, and hydraulic fracturing is performed in the test borehole 8. The original apparent resistivity sequence set and the first apparent resistivity sequence set measured before and after the construction of the test borehole 8 are compared to determine the average effective fracturing height of the test borehole 8 in the pressure relief area 4. and the average effective fracture width And according to the average effective fracturing width of the test borehole 8 in the pressure relief area 4 Determine the number of columns of decompression boreholes to be constructed, based on the average effective fracturing height of the test boreholes 8 in the decompression area 4 The number of pressure relief boreholes 9 included in each column of pressure relief boreholes is determined.

[0113] In this embodiment, when The average effective fracturing height of test borehole 8 is shown as It cannot cover the maximum height of the pressure relief area 4. If only one pressure relief borehole 9 is constructed in each row, it is difficult to achieve the ideal pressure relief effect after the pressure relief area 4 is relieved. When two pressure relief holes 9 are constructed in each row, the pressure relief area 4 is effectively relieved, saving time and effort; The average effective fracturing height of test borehole 8 is shown as The height that can cover the hard roof 2 of the coal seam, theoretically, one pressure relief borehole 9 is constructed in each row, and the pressure relief area 4 can achieve an ideal pressure relief effect after the pressure relief is completed.

[0114] In this embodiment, the area to be depressurized 4 includes a depressurization section 4-1 and a safety section 4-2. The test borehole 8 and the depressurization borehole 9 are both located in the depressurization section 4-1. The safety section 4-2 is located between the depressurization section 4-1 and the working face opening. The distance between the end position of the test borehole 8 and the working face opening is the length of the safety section 4-2. By setting the safety section 4-2, it is avoided that the normal operation of the working face opening is affected when the test borehole 8 and the depressurization borehole 9 are injected with water in the depressurization section 4-1, and a safety range is left, which has good safety.

[0115] In this embodiment, the test borehole 8 and the pressure relief borehole 9 are both directional long-distance boreholes. The diameter of the pressure relief borehole 9 is equal to the diameter of the test borehole 8. The starting position of the pressure relief borehole 9 is the same as the starting position of the test borehole 8. The ending position of the pressure relief borehole 9 is the same as the ending position of the test borehole 8.

[0116] In this embodiment, hydraulic fracturing is implemented in the pressure relief borehole 9 to pre-form multiple fracturing cracks in the pressure relief area 4, so that the strength of the hard roof 2 of the coal seam is reduced along the crack direction, which makes the hard roof 2 of the coal seam easy to collapse, reduces the hanging length of the hard roof 2 of the coal seam, and thus the impact ground pressure strength of the hard roof 2 of the coal seam.

[0117] In this embodiment, in step 4, the average development height of the internal cracks in the area to be unloaded after unloading is measured, and the specific process is as follows:

[0118] Step 401: According to the method described in step 302, the apparent resistivity of the area to be depressurized 4 is measured again at M groups of measuring points to obtain a second apparent resistivity sequence set of M areas to be depressurized 4; wherein the apparent resistivity of the area to be depressurized 4 is measured at the m-th group of measuring points to obtain a second apparent resistivity sequence set ρ of the area to be depressurized 4 at the m-th group of measuring points 2m , the second apparent resistivity series set ρ 2m A second apparent resistivity sequence set ρ 2m The ath second apparent resistivity is denoted as ρ 2ma ;

[0119] Step 402: According to the method described in step 303, the second apparent resistivity sequence set and the original apparent resistivity sequence set at the M groups of measuring points are processed to obtain the effective fracturing area and effective fracturing height of the N columns of pressure relief boreholes 9 at the M groups of measuring points; wherein the effective fracturing height of the nth column of pressure relief boreholes 9 at the mth group of measuring points is h 2mn , n is a positive integer, and 1≤n≤N;

[0120] Step 403: According to the formula Calculate the average effective fracturing height of N rows of pressure relief boreholes at the mth group of measuring points

[0121] Step 404: According to the formula Calculate the average fracturing height of N rows of decompression boreholes in the decompression area 4 Then the average development height H of the internal cracks in the area to be unloaded after unloading is obtained. 2 ,

[0122] In this embodiment, it should be noted that the effective fracturing height of the nth column of relief boreholes 9 at the mth group of measuring points in step 402 refers to the sum of the effective fracturing heights of all relief boreholes 9 in the nth column of relief boreholes 9 at the mth group of measuring points.

[0123] In this embodiment, in step 4, the apparent resistivity of the area to be unloaded 4 after the pressure relief is completed is measured by the transient electromagnetic instrument 7 to obtain a second apparent resistivity sequence set, and the original apparent resistivity sequence set collected before and after the pressure relief in the area to be unloaded 4 and the second apparent resistivity sequence set are compared to obtain the average development height H of the cracks in the area to be unloaded 4 2 , the average development height H of the cracks in the area to be relieved 4 2 is the average fracturing height of N rows of pressure relief boreholes at M groups of measuring points The average value of the average development height H of the cracks in the area to be relieved 4 2 It can effectively and accurately represent the development height of the internal cracks of the entire pressure relief area 4 after the pressure relief is completed, and the measurement result has good accuracy.

[0124] In this embodiment, in step 5, the pressure relief impact hazard level of the pressure relief area to be relieved is determined according to the average development height of the internal cracks in the pressure relief area after pressure relief. The specific process is as follows:

[0125] When 0.1H 1 ≤H 2 ≤0.8H 1 When the impact hazard level of the area 4 to be depressurized is level I, execute step 6;

[0126] When 0.8H 1 <H 2 <H 1 When the impact hazard level of the area 4 to be depressurized is level II, execute step 7;

[0127] When H 2 ≥H 1 When the impact hazard level of the area 4 to be depressurized is level III, execute step eight;

[0128] The risk of the level I impact hazard is higher than that of the level II impact hazard, and the risk of the level II impact hazard is higher than that of the level III impact hazard.

[0129] In this embodiment, it should be noted that in step 5, the average development height H of the internal cracks in the area to be unloaded after unloading is determined. 2 The maximum height H of the pressure relief area 4 1 The impact hazard level of the area 4 to be decompressed is determined by the relationship between the size of H 2 ≥H 1 When the pressure relief area 4 is less affected by the stress disturbance of the mining face 1, it meets the impact hazard level required by the construction. At this time, the impact hazard level of the pressure relief area 4 is level III impact hazard; when 0.8H 1 <H 2 <H 1 When the pressure is released, the impact of the stress disturbance of the mining face 1 on the unloading area 4 increases. At this time, the impact hazard level of the unloading area 4 is level II, which does not meet the impact hazard level required by the construction. 1 ≤H 2 ≤0.8H 1 , the area 4 to be depressurized after depressurization is highly affected by the stress disturbance of the coal mining face 1. At this time, the impact hazard level of the area 4 to be depressurized is Level I impact hazard, which does not meet the impact hazard level required by the construction.

[0130] In this embodiment, in step six, the diameter of the pressure relief borehole in the pressure relief area is adjusted and pressure relief is performed again. The specific process is as follows:

[0131] The diameter d of the pressure relief hole 9 in the pressure relief area 4 is 1 Increase Δd to obtain a pressure relief borehole with an increased aperture, perform hydraulic fracturing in the pressure relief borehole with an increased aperture, and regard the pressure relief borehole with an increased aperture as pressure relief borehole 9, and repeat step 4; wherein,

[0132] In this embodiment, when the impact hazard level of the area to be depressurized 4 is Level I impact hazard, it means that the height of the fracturing cracks generated by the hydraulic fracturing in the depressurization borehole 9 is relatively small, resulting in poor overall depressurization effect in the area to be depressurized 4. It is necessary to increase the aperture of the depressurization borehole 9, and implement hydraulic fracturing again in the depressurization borehole with the increased aperture.

[0133] In this embodiment, in step seven, additional pressure relief is performed on the area to be relieved, and the specific process is as follows:

[0134] According to the effective fracturing area of ​​the N columns of pressure relief boreholes at the mth group of measuring points in step 402, the ineffective fracturing area at the mth group of measuring points after pressure relief is determined, and the ineffective fracturing area at the mth group of measuring points is regarded as the ineffective fracturing area of ​​the area 4 to be relieved, the number of ineffective fracturing areas is Q, and the Q ineffective fracturing areas are all supplemented with pressure relief; wherein, the judgment basis of the ineffective fracturing area at the mth group of measuring points is: the area in the area 4 to be relieved at the mth group of measuring points except the effective fracturing area of ​​the N columns of pressure relief boreholes 9 is the ineffective fracturing area at the mth group of measuring points, Q is a positive integer, and Q ≥ 1, the method of supplementing the pressure relief of the Q ineffective fracturing areas is the same, and when the qth ineffective fracturing area is supplemented with pressure relief, the following steps are mainly included:

[0135] Step 701: Measure the maximum width b of the qth ineffective fracturing area. 3max and the maximum height h 3max ;

[0136] Step 702: Determine the number of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area:

[0137] According to the formula The number of columns L of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is calculated.

[0138] According to the formula The number P of supplementary pressure relief boreholes in each column of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is calculated, and then the number of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is determined. The number of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is L×P; wherein, Indicates rounding up;

[0139] Step 703: construct L×P supplementary pressure relief boreholes in the qth ineffective fracturing area, and perform hydraulic fracturing in the L×P supplementary pressure relief boreholes to complete the supplementary pressure relief in the qth ineffective fracturing area; wherein the structure of the supplementary pressure relief borehole is the same as that of the test borehole 8, and the aperture of the supplementary pressure relief borehole is d 2 , d 2 =d 1 ;

[0140] Step 704, according to the method described in step 302, the apparent resistivity of the area 4 to be depressurized is measured again at M groups of measuring points to obtain a third apparent resistivity sequence set of M areas 4 to be depressurized;

[0141] Step 705: According to the method described in step 303, data processing is performed on the third apparent resistivity sequence set and the second apparent resistivity sequence set at the M group of measuring points to obtain the effective fracturing area and effective fracturing height of the L column of supplementary pressure relief boreholes at the M group of measuring points; wherein the effective fracturing height of the pressure relief borehole 9 in the lth column at the mth group of measuring points is h 3ml ; Wherein, l is a positive integer, and 1≤l≤L;

[0142] Step 706: According to the formula Calculate the average effective fracturing height of L rows of supplementary pressure relief boreholes at the mth group of measuring points

[0143] Step 707: According to the formula Calculate the average fracturing height of L rows of supplementary decompression boreholes in the decompression area 4 Then the average development height H of the internal cracks in the qth non-effective fracturing area after supplementary unloading is obtained: 3 ,

[0144] Step 708: Determine the average development height H of the internal cracks in the qth ineffective fracturing area after the supplementary unloading. 3 Is it less than the maximum height h of the qth ineffective fracturing area? 3max , if H 3 <h 3max , execute step 709; otherwise, execute step eight;

[0145] Step 709: Set the diameter d of the additional pressure relief borehole in the qth ineffective fracturing area. 2 Increase Δd to obtain a supplementary pressure relief borehole with an increased aperture, perform hydraulic fracturing in the supplementary pressure relief borehole with an increased aperture, and regard the supplementary pressure relief borehole with an increased aperture as a supplementary pressure relief borehole, and loop step 704.

[0146] In this embodiment, when the impact hazard level of the area to be unloaded 4 is level II impact hazard, it means that the height of the fracturing cracks generated by the hydraulic fracturing in the unloading borehole 9 is average, resulting in an average overall unloading effect in the area to be unloaded 4. It is necessary to drill a supplementary unloading borehole in the non-effective fracturing area of ​​the area to be unloaded 4, and implement hydraulic fracturing in the supplementary unloading borehole to fracture the non-effective fracturing area, so that the non-effective fracturing area is converted into an effective fracturing area.

[0147] In this embodiment, the pressure relief in the area to be relieved is completed in step eight, and the specific process is as follows:

[0148] Hydraulic fracturing is performed again in all the pressure relief boreholes 9 to complete the pressure relief in the area 4 to be relieved.

[0149] In this embodiment, the starting position and the ending position of the test borehole 8 in step 301 are both located in front of the cut hole of the working face. The starting position of the test borehole 8 is determined by the width of the coal mining working face 1, and the distance L between the starting position of the test borehole 8 and the cut hole of the working face is 1 =2B 0 +L 0 , B 0 is the width of coal mining face 1, L 0 To test the distance between the end position of the drill hole 8 and the cut hole on the working surface, L 0 The value range is 20m~40m.

[0150] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for controlling rock burst in a hard roof of a coal mine tunnel, characterized in that: The method comprises the following steps: Step 1: Determine the location of the area to be depressurized; Step 2: collecting the original apparent resistivity of the area to be depressurized before depressurization; Step 3, depressurizing the area to be depressurized; Step 4: measuring the average development height of the internal cracks in the area to be depressurized after depressurization; Step 5: Determine the pressure relief impact hazard level of the pressure relief area according to the average development height of the internal cracks in the pressure relief area after pressure relief; Step 6: Adjust the diameter of the pressure relief borehole in the pressure relief area and perform pressure relief again; Step 7: Supplementary pressure relief to the pressure relief area; Step 8: Complete the pressure relief in the area to be relieved; In step 2, the original apparent resistivity of the area to be depressurized is collected before depressurization. The specific process is as follows: Step 201: M groups of measuring points are arranged in sequence from back to front along the length direction of the coal mining working face (1), each group of measuring points includes a first measuring point (10) located in the transport tunnel (5) and a second measuring point (11) located in the return air tunnel (6); wherein M is a positive integer, and M≥3; Step 202, measuring the apparent resistivity of the area to be relieved (4) at M groups of measuring points respectively, to obtain a set of original apparent resistivity sequences of the M areas to be relieved (4), wherein the measuring methods of the apparent resistivity of the areas to be relieved (4) at the M groups of measuring points are the same, and when measuring the apparent resistivity of the area to be relieved (4) at the mth group of measuring points, the following steps are included: Step 2021, placing the transient electromagnetic instrument (7) at the first measuring point (10) of the m-th group of measuring points, so that the plane where the transmitting coil of the transient electromagnetic instrument (7) is located is parallel to the vertical plane where the central axis of the transport tunnel (5) is located, and then rotating the transmitting coil of the transient electromagnetic instrument (7) 90° clockwise. During the rotation of the transmitting coil of the transient electromagnetic instrument (7), the transient electromagnetic instrument (7) measures the apparent resistivity of the area to be depressurized (4) according to the set measurement interval, and obtains the original apparent resistivity of the area to be depressurized (4) at different angles at the first measuring point (10) of the m-th group of measuring points; wherein m is the measuring point number, 1≤m≤M, and the measurement interval is 10° to 15°; Step 2022, placing the transient electromagnetic instrument (7) at the second measuring point (11) of the m-th group of measuring points, so that the plane where the transmitting coil of the transient electromagnetic instrument (7) is located is arranged parallel to the vertical plane where the central axis of the return air tunnel (6) is located, and then rotating the transmitting coil of the transient electromagnetic instrument (7) counterclockwise by 90°. During the rotation of the transmitting coil of the transient electromagnetic instrument (7), the transient electromagnetic instrument (7) measures the apparent resistivity of the area to be depressurized (4) according to the set measurement interval, and obtains the original apparent resistivity of the area to be depressurized (4) at different angles at the second measuring point (11) of the m-th group of measuring points; Step 2023: Arrange the original apparent resistivity of the area to be depressurized (4) at different angles at the first measuring point (10) of the m-th group of measuring points obtained in step 2021 and the original apparent resistivity of the area to be depressurized (4) at different angles at the second measuring point (11) of the m-th group of measuring points obtained in step 2022 in the order of measurement time to obtain an original apparent resistivity sequence set ρ of the area to be depressurized (4) at the m-th group of measuring points. 0m , the original apparent resistivity series set ρ 0m It includes A original apparent resistivity, and the original apparent resistivity sequence set ρ 0m The ath original apparent resistivity is denoted as ρ 0ma ; Where A is a positive integer, a is the original apparent resistivity number, 1≤a≤A; In step 3, the pressure in the area to be relieved is relieved. The specific process is as follows: Step 301, determining the aperture d1, the starting position and the ending position of a test borehole (8) to be constructed in the area to be depressurized (4), constructing a test borehole (8) in the area to be depressurized (4), and performing hydraulic fracturing in the test borehole (8); wherein the test borehole (8) is arranged close to the left end of the area to be depressurized (4), and the center of the test borehole (8) is located on the horizontal center line of the area to be depressurized (4); Step 302: According to the method described in step 202, the apparent resistivity of the area to be depressurized (4) is measured again at M groups of measuring points to obtain a first apparent resistivity sequence set of M areas to be depressurized (4); wherein the apparent resistivity of the area to be depressurized (4) at the mth group of measuring points is measured to obtain a first apparent resistivity sequence set ρ of the area to be depressurized (4) at the mth group of measuring points 1m , the first apparent resistivity sequence set ρ 1m A first apparent resistivity sequence set ρ 1m The ath first apparent resistivity is denoted as ρ 1ma ; Step 303: Data processing is performed on the first apparent resistivity sequence set and the original apparent resistivity sequence set at the M group of measuring points to obtain the effective fracturing width and effective fracturing height of the test borehole (8) at the M group of measuring points. The data processing method for the first apparent resistivity sequence set and the original apparent resistivity sequence set at the M group of measuring points is the same. The first apparent resistivity sequence set ρ at the mth group of measuring points is processed. 1m and the original apparent resistivity series set ρ 0m The data processing includes the following steps: Step 3031: For the first apparent resistivity sequence set ρ 1m The A first apparent resistivity and original apparent resistivity series set ρ 0m The A original apparent resistivities in the mth group are matched one by one, and the decrease of the A first apparent resistivities at the mth group of measuring points is calculated respectively; among them, the calculation method of the decrease of the A first apparent resistivities is the same. When calculating the decrease of the ath first apparent resistivity, the formula is used. The decrease J of the ath first apparent resistivity is calculated 1a ; Step 3032: According to the A first apparent resistivity drop amplitudes and the first apparent resistivity sequence set ρ 1m The effective fracturing area of ​​the test borehole (8) at the mth group of measuring points is determined by the A first apparent resistivity in the test borehole (8); wherein the effective fracturing area of ​​the test borehole (8) is divided according to: when the ath first apparent resistivity ρ 1ma ≤35Ω·m, and the ath first apparent resistivity ρ 1ma The decline in 1a When ≥50%, the area corresponding to the ath first apparent resistivity is located within the effective fracturing area of ​​the test borehole (8); Step 3033: measure the average width of the effective fracturing area of ​​the test borehole (8) at the mth group of measuring points as the effective fracturing width b of the test borehole (8) at the mth group of measuring points. 1m , measure the average height of the effective fracturing area of ​​the test borehole (8) at the mth group of measuring points as the effective fracturing height h of the test borehole (8) at the mth group of measuring points 1m ; Step 304: According to the formula Calculate the average effective fracturing height of the test borehole (8) in the area to be depressurized (4) According to the formula Calculate the average effective fracturing width of the test borehole (8) in the area to be depressurized (4) when When , execute step 305, when When , step 306 is executed; wherein H1 is the maximum height of the area to be depressurized (4); Step 305: construct N rows of pressure relief boreholes along the length direction of the pressure relief area (4), each row of pressure relief boreholes includes a pressure relief borehole (9), and perform hydraulic fracturing in the N pressure relief boreholes (9) to complete the pressure relief of the pressure relief area (4); wherein: represents rounding up, B1 is the maximum width of the pressure relief area (4), the structure of the pressure relief borehole (9) is the same as that of the test borehole (8), the centers of the plurality of pressure relief boreholes (9) and the center of the test borehole (8) are located on the same straight line, and the hole spacing between two adjacent rows of pressure relief boreholes is k1, Step 306: construct N rows of pressure relief boreholes along the length direction of the pressure relief area (4), each row of pressure relief boreholes including two pressure relief boreholes (9), and implement hydraulic fracturing in the 2N pressure relief boreholes (9) to complete the pressure relief of the pressure relief area (4); wherein the two pressure relief boreholes (9) in each row of pressure relief boreholes (9) are respectively located at the upper and lower sides of the test borehole (8), and the hole spacing between the two pressure relief boreholes (9) in each row of pressure relief boreholes is k2, In step 5, the pressure relief impact hazard level of the area to be relieved is determined based on the average development height of the internal cracks in the area to be relieved after pressure relief. The specific process is as follows: When 0.1H1≤H2≤0.8H1, the impact hazard level of the area to be depressurized (4) is level I impact hazard, and step 6 is executed; When 0.8H1<H2<H1, the impact hazard level of the area to be depressurized (4) is level II impact hazard, and step 7 is executed; When H2≥H1, the impact hazard level of the area to be depressurized (4) is level III impact hazard, and step eight is executed; The risk of the level I impact hazard is higher than that of the level II impact hazard, and the risk of the level II impact hazard is higher than that of the level III impact hazard.

2. A method for controlling rock burst in a hard roof of a coal mine tunnel according to claim 1, characterized in that: In step 1, the location of the area to be depressurized is determined. The specific process is as follows: The layer position of the hard roof (2) of the coal seam overlying the coal mining working face (1) is determined, and the area of ​​the hard roof (2) of the coal seam located in the vertical downward movement area (3) is the area to be depressurized (4).

3. A method for controlling rock burst in a hard roof of a coal mine tunnel according to claim 1, characterized in that: In step 4, the average height of the internal cracks in the area to be unloaded is measured after unloading. The specific process is as follows: Step 401: According to the method described in step 302, the apparent resistivity of the area to be depressurized (4) is measured again at M groups of measuring points to obtain a second apparent resistivity sequence set of M areas to be depressurized (4); wherein the apparent resistivity of the area to be depressurized (4) is measured at the m-th group of measuring points to obtain a second apparent resistivity sequence set ρ of the area to be depressurized (4) at the m-th group of measuring points. 2m , the second apparent resistivity series set ρ 2m A second apparent resistivity sequence set ρ 2m The ath second apparent resistivity is denoted as ρ 2ma ; Step 402: According to the method described in step 303, data processing is performed on the second apparent resistivity sequence set and the original apparent resistivity sequence set at the M groups of measuring points to obtain the effective fracturing area and effective fracturing height of the N columns of pressure relief boreholes (9) at the M groups of measuring points; wherein the effective fracturing height of the nth column of pressure relief boreholes (9) at the mth group of measuring points is h 2mn , n is a positive integer, and 1≤n≤N; Step 403: According to the formula Calculate the average effective fracturing height of N rows of pressure relief boreholes at the mth group of measuring points Step 404: According to the formula Calculate the average fracturing height of N rows of decompression boreholes in the decompression area (4) Then the average development height H2 of the internal cracks in the area to be unloaded after unloading is obtained.

4. A method for controlling rock burst in a hard roof of a coal mine tunnel according to claim 3, characterized in that: In step 6, the diameter of the pressure relief borehole in the pressure relief area is adjusted and pressure relief is performed again. The specific process is as follows: The aperture d1 of the pressure relief borehole (9) in the pressure relief area (4) is increased by Δd to obtain a pressure relief borehole with an increased aperture, hydraulic fracturing is performed in the pressure relief borehole with an increased aperture, and the pressure relief borehole with an increased aperture is regarded as the pressure relief borehole (9), and step four is repeated; wherein Δd=5cm-10cm.

5. A method for controlling rock burst in a hard roof of a coal mine tunnel according to claim 3, characterized in that: In step seven, additional pressure relief is performed on the area to be relieved. The specific process is as follows: According to the effective fracturing area of ​​the N rows of pressure relief boreholes at the mth group of measuring points in step 402, the ineffective fracturing area at the mth group of measuring points after pressure relief is determined, and the ineffective fracturing area at the mth group of measuring points is regarded as the ineffective fracturing area of ​​the area to be relieved (4), the number of ineffective fracturing areas is Q, and the Q ineffective fracturing areas are all supplemented with pressure relief; wherein, the basis for determining the ineffective fracturing area at the mth group of measuring points is: the area except the effective fracturing area of ​​the N rows of pressure relief boreholes (9) in the area to be relieved (4) at the mth group of measuring points is the ineffective fracturing area at the mth group of measuring points, Q is a positive integer, and Q≥1, the method for supplementing the pressure relief of the Q ineffective fracturing areas is the same, and when supplementing the pressure relief of the qth ineffective fracturing area, the following steps are included: Step 701: Measure the maximum width b of the qth ineffective fracturing area. 3max and the maximum height h 3max ; Step 702: Determine the number of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area: According to the formula The number of columns L of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is calculated. According to the formula The number P of supplementary pressure relief boreholes in each column of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is calculated, and then the number of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is determined. The number of supplementary pressure relief boreholes to be constructed in the qth ineffective fracturing area is L×P; wherein, Indicates rounding up; Step 703, constructing L×P supplementary pressure relief boreholes in the qth ineffective fracturing area, and performing hydraulic fracturing in the L×P supplementary pressure relief boreholes, to complete the supplementary pressure relief in the qth ineffective fracturing area; wherein the structure of the supplementary pressure relief borehole is the same as that of the test borehole (8), and the aperture of the supplementary pressure relief borehole is d2, d2=d1; Step 704: According to the method described in step 302, the apparent resistivity of the area to be depressurized (4) is measured again at M groups of measuring points to obtain a third apparent resistivity sequence set of the M areas to be depressurized (4); Step 705: According to the method described in step 303, data processing is performed on the third apparent resistivity sequence set and the second apparent resistivity sequence set at the M groups of measuring points to obtain the effective fracturing area and effective fracturing height of the L columns of supplementary pressure relief boreholes at the M groups of measuring points; wherein the effective fracturing height of the lth column of pressure relief boreholes (9) at the mth group of measuring points is h 3ml ; Wherein, l is a positive integer, and 1≤l≤L; Step 706: According to the formula Calculate the average effective fracturing height of L rows of supplementary pressure relief boreholes at the mth group of measuring points Step 707: According to the formula Calculate the average fracturing height of L rows of supplementary decompression boreholes in the decompression area (4) Then the average development height H3 of the internal fractures in the qth non-effective fracturing area after supplementary unloading is obtained. Step 708: Determine whether the average development height H3 of the internal cracks of the qth ineffective fracturing area after the supplementary unloading is less than the maximum height h 3max , if H3<h 3max , execute step 709; otherwise, execute step eight; Step 709, increase the aperture d2 of the supplementary pressure relief borehole in the qth non-effective fracturing area by Δd to obtain a supplementary pressure relief borehole with an increased aperture, perform hydraulic fracturing in the supplementary pressure relief borehole with an increased aperture, and regard the supplementary pressure relief borehole with an increased aperture as a supplementary pressure relief borehole, and loop step 704.

6. A method for controlling rock burst in a hard roof of a coal mine tunnel according to claim 1, characterized in that: In step eight, the pressure relief in the area to be relieved is completed. The specific process is as follows: Hydraulic fracturing is performed again in all the pressure relief boreholes (9) to complete the pressure relief in the area to be relieved (4).

7. A method for controlling rock burst in a hard roof of a coal mine tunnel according to claim 1, characterized in that: In step 301, the starting position and the ending position of the test borehole (8) are both located in front of the cut hole of the working face. The starting position of the test borehole (8) is determined by the width of the coal mining working face (1). The distance L1 between the starting position of the test borehole (8) and the cut hole of the working face is 2B0+L0, where B0 is the width of the coal mining working face (1), and L0 is the distance between the ending position of the test borehole (8) and the cut hole of the working face. The value range of L0 is 20m to 40m.

Images