Method for identifying and grading rock burst in mines based on equivalent depth

Abstract

The present invention relates to a method for identifying and grading rock burst mines based on equivalent depth, and belongs to the field of prevention of rock burst disasters in coal mining. The present invention proposes to use the mining depth of the mine as a basic indicator, and consider four types of geological factors, namely coal seam factors, geological structure factors, impact tendency factors, and overlying rock factors, to obtain the equivalent depth of the mine. By comparing the equivalent depth of the mine with the critical depth at which rock burst occurs, it is determined whether the mine is rock burst and the grade is divided. Grading management measures are taken for different grades, thereby achieving the goal of graded management of rock burst mines. The method is scientific, simple, intuitive, and highly operable. It can be used as a method for identifying and grading rock burst mines by rock burst mine identification units, as well as to guide coal mine safety production and serve as an important basis for coal mine safety supervision, inspection, and rock burst prevention and control. It is of great significance to avoiding coal mine rock burst accidents and ensuring coal mine safety production.

Description

Technical Field

[0001] The present invention belongs to the field of prevention of rock burst disasters in coal mining, and in particular relates to a method for identifying and grading rock burst mines based on equivalent depth. Background Art

[0002] With increasing energy demand and mining depths in my country, the majority of mines will enter deep mining in the coming decades. Deep coal mining, characterized by complex geological conditions, is increasingly associated with rock burst disasters. Rock bursts are sudden, instantaneous, and extremely destructive, causing significant property losses and casualties to coal mine safety. Therefore, determining whether a mine is a rock burst site is a crucial prerequisite and foundation for rock burst prevention and control. Scientifically identifying rock burst sites and categorizing rock burst sites has become a critical requirement for safe deep coal mining.

[0003] At present, rock burst mines in my country are identified based on the occurrence of rock burst dynamic phenomena or the results of coal seam rock burst tendency identification and rock burst hazard assessment. The rock burst dynamic phenomena are difficult to determine. If a rock burst accident occurs and then a mine is determined to be a rock burst mine, it will have caused significant property losses or casualties. The method of coal seam rock burst tendency identification and rock burst hazard assessment is difficult to adapt to the current coal mining conditions under the new situation in my country. The method is complex, has many influencing factors, and is greatly affected by human factors, resulting in an unscientific identification process for rock burst mines, causing rock burst in non-rock burst mines or excessive rock burst prevention and control, which brings troubles and difficulties to rock burst prevention and control in mines.

[0004] Research has found that the occurrence of rock burst is influenced by a combination of geological factors, including mining depth, coal seam factors, geological structure factors, rock burst propensity factors, and overlying rock strata factors. Rock burst is a controlling variable that influences whether a mine experiences rock burst, an objective and unchanging factor, and an internal cause of rock burst. Therefore, proposing a method for identifying and grading rock burst mines based on mining depth, and thereby scientifically standardizing the process of identifying and grading rock burst mines, is an important prerequisite for determining whether and to what extent rock burst prevention and control measures should be implemented in current mines. It is also an important research direction for the development of rock burst source control and is of great significance for preventing property losses and casualties caused by rock burst disasters. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to propose a method for identifying and grading rock burst mines based on equivalent depth, so as to achieve the purpose of scientifically, simply and intuitively determining whether a mine is a rock burst mine.

[0006] The object of the present invention is achieved through the following technical solution: a method for identifying and grading rock burst mines based on equivalent depth, comprising the following steps:

[0007] Step 1: Parameter collection. Collect the geological environment parameters of the mine, including the thickness, inclination, and coefficient of variation of the coal seam factors; the complexity of the mine geological structure and the ratio of the stress increment to the normal stress value in the geological structure factors; the impact tendency results of the coal seam and the roof and floor in the impact tendency factors; the thickness characteristic parameters of the roof rock layer above the coal seam in the overburden rock layer factors; the distance parameters of the hard thick rock layer in the fracture zone from the coal seam; the uniaxial compressive strength of coal in each coal seam; the bulk density of the overburden rock layer (which can be calculated using the average bulk density of the rock or based on the actual mine stratum comprehensive histogram), the impact energy index of the coal, and the mining depth of the mining working face during the mine planning period;

[0008] Step 2: Calculate the critical depth of rock burst. Calculate the critical depth H of rock burst in the mine according to formula (1): cr :

[0009]

[0010] Where, σ c is the uniaxial compressive strength of the coal body, in MPa; γ is the bulk density of the overlying rock strata, which can be calculated using the average bulk density of the rock or based on the comprehensive histogram of the mine strata, in MP / m; K E is the impact energy index of coal, which is obtained based on the impact tendency of coal and is dimensionless; η1 is the correction coefficient, which is related to the uniaxial compressive strength of coal. When multiple coal seams are mined, the critical depths for rock burst are calculated separately, and the minimum critical depth is selected as the indicator for the identification method of the present invention.

[0011] Step 3: Calculate the equivalent depth. Taking the maximum mining depth h of the mining face during the mine planning period as the basic indicator, the equivalent depth is obtained by considering the coal seam factors, geological structure factors, impact tendency factors, and overlying rock factors. The equivalent depth H is calculated using the formula (2):

[0012] H=(1+q1L1+q2L2+q3L3+q4L4)×h (2)

[0013] In the formula, each parameter is determined according to the planned mining working face of the mine in the next three years, h is the maximum depth of the working face during the mine planning period, in meters; q1 is the weight of the coal seam factor, dimensionless; L1 is the value of the coal seam factor, dimensionless; q2 is the weight of the geological structure factor, dimensionless; L2 is the value of the geological structure factor, dimensionless; q3 is the weight of the impact tendency factor, dimensionless; L3 is the value of the impact tendency factor, dimensionless; q4 is the weight of the overburden stratum factor, dimensionless; L4 is the value of the overburden stratum factor, dimensionless.

[0014] The calculation process of coal seam factor weight q1, geological structure factor weight q2, impact tendency factor weight q3, and overlying rock stratum factor weight q4 is as follows:

[0015] ① Construct the judgment matrix of rock burst influencing factors. According to the rock burst situation of the mine, the four types of factors for judging the mine are compared in pairs to obtain the importance of the occurrence of rock burst in the mine, and the judgment matrix P of each factor is constructed. ij The following formula (3):

[0016]

[0017] Among them, the right diagonal elements of the matrix P 12 It indicates the importance of coal seam factors compared with geological structure factors in determining mine rock burst; P 13 It indicates the importance of coal seam factors compared with the impact tendency factors in determining the impact rock pressure in the mine; P 14 P represents the importance of coal seam factors compared with overlying rock factors in determining mine rock burst; 23 It indicates the importance of geological structural factors compared with impact tendency factors in determining rock burst in mines; P 24 It indicates the importance of geological structure factors compared with overlying rock factors in determining mine rock burst; P 33 It indicates the importance of the impact tendency factor compared with the overlying rock strata factor in determining the impact rock pressure in the mine; similarly, the definition of the left diagonal elements of the matrix is opposite to that of the right diagonal elements, and its value is the reciprocal of the right diagonal value.

[0018] P ij The value range of each element in the matrix is an integer between 1 and 9 or its reciprocal; 1 means that the two elements have the same importance; 3 means that the former is slightly more important than the latter; 5 means that the former is obviously more important than the latter; 7 means that the former is strongly more important than the latter; 9 means that the former is extremely more important than the latter; other values represent the degree of importance between adjacent importance levels; similarly, the reciprocal of the integer between 1 and 9 represents the degree of importance of the latter over the former.

[0019] ② Calculate the weight q of each influencing factor: Calculate the weight of the four factors as shown in formula (4);

[0020]

[0021] In the formula, i ranges from 1 to 4, corresponding to the coal seam factor weight value q1, the geological structure factor weight value q2, the impact tendency factor weight value q3 and the overlying rock stratum factor weight value q4.

[0022] The value range of coal seam factor L1, geological structure factor value L2, impact tendency factor value L3, and overburden stratum factor value L4 is 0 to 1, and the value selection process is as follows:

[0023] ① The coal seam factor is divided into three sub-factors: coal mine thickness factor, inclination factor, and coal seam thickness variation factor. The value range of the three sub-factor indicators is divided, and the value result of the coal seam factor L1 is obtained by comparing it with the actual situation of the mine. The coal seam factor L1 = coal seam thickness factor L 11 + Coal seam dip factor L 12 + Coal thickness variation factor L 13 .

[0024] ② The geological structure factor is divided into two sub-factors: the complexity of the mine geological structure and the ratio of the stress increment caused by the structure to the normal stress value. The value range of the two sub-factor indicators is divided, and the value result of the geological structure factor L2 is obtained by comparing it with the actual situation of the mine. The geological structure factor L2 = the complexity of the mine geological structure L 21 +Ratio of stress increment caused by construction to normal stress value L 22 .

[0025] ③ Impact tendency factor L3 is divided into three sub-factors: coal impact tendency factor, roof rock impact tendency factor, and floor rock impact tendency factor. The three sub-factor index value ranges are divided and compared with the actual situation of the mine to obtain the impact tendency factor value results. Impact tendency factor L3 = coal impact tendency factor L 31 + Roof rock impact tendency factor L 32 +Floor rock impact tendency factor L 33 .

[0026] ④ The overlying rock layer factor L4 is divided into two sub-factors: the characteristic parameter factor of the thickness of the roof rock layer above the coal seam and the distance factor of the hard thick rock layer in the overlying fracture zone from the coal seam. The value range of the two sub-factor indicators is divided, and the overlying rock layer factor value result is obtained by comparing with the actual situation of the mine. The overlying rock layer factor L4 = the characteristic parameter factor L of the thickness of the roof rock layer above the coal seam 41 +The distance factor L between the hard and thick rock layer in the overlying fracture zone and the coal seam 42 .

[0027] Step 4: Determine whether the mine is a rock burst mine. cr For comparison, when the mine equivalent depth H≥H cr When the mine is at a depth of H <H cr When the mine is judged to be a non-rock burst mine.

[0028] Step 5: Identify the rock burst mine grade. When a mine is identified as a rock burst mine, the rock burst mine grade is divided into three levels: weak rock burst mine, medium rock burst mine, and strong rock burst mine.

[0029] When H cr ≤H<1.5H cr When , it is judged to be a weak rock burst mine;

[0030] When 1.5H cr ≤H<2H cr When the rock burst is detected, it is judged as a medium rock burst mine;

[0031] When H≥2H cr When the mine is detected, it is judged to be a mine with strong rock burst.

[0032] The beneficial effects of the present invention are as follows: The present invention uses the mining depth of a mine as a basic indicator, considers four factors: coal seam factors, geological structure factors, impact propensity factors, and overlying rock factors, to obtain the equivalent depth of the mine. By calculating the critical depth at which rock burst occurs in the mine, the equivalent depth and the critical depth are compared. When the equivalent depth of the mine is greater than or equal to the critical depth at which rock burst occurs, the mine is identified as a rock burst mine; when the equivalent depth of the mine is less than the critical depth at which rock burst occurs, the mine is identified as a non-rock burst mine. For rock burst mines, the rock burst level is determined by determining whether the equivalent depth is within the critical depth range. The above scheme realizes the identification and grading of rock burst mines, and adopts graded management measures for different levels to achieve the goal of graded management of rock burst mines. The scheme is scientific, simple, intuitive, and highly operational. It can be used as a method for identifying rock burst mines, guiding coal mine safety production, and serving as an important basis for coal mine safety supervision, inspection, and rock burst prevention and control. It is of great significance for avoiding coal mine rock burst accidents and ensuring coal mine safety production. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart for identifying and grading rock burst mines based on equivalent depth. DETAILED DESCRIPTION

[0034] Step S1: Collect the basic parameters of a coal mine. The coal mine is a single coal seam mining. Through the mine rock burst analysis, based on the mining working face conditions in the next three-year planning period of the coal mine, it was collected that the average thickness of the coal seam is 6.5m, the average inclination of the coal seam is 3°, and the coefficient of variation of the coal seam thickness is 0.22. After consulting the mine geological description, it was found that the mine geological structure complexity is medium; after consulting the mine ground stress test report, it was found that the maximum principal stress of the mine is 31.2MPa; after consulting the coal seam rock burst tendency identification report, it was found that the coal burst tendency is strong, the roof rock burst tendency is weak, and the bottom rock burst has no burst tendency; after consulting the mine comprehensive histogram and combining the geological drilling histogram, it was found that the characteristic parameter of the roof rock thickness above the coal seam is 62m, the distance between the hard and thick rock layer in the overlying fracture zone and the coal seam is 40m; and the uniaxial compressive strength of the coal is σ c The pressure is 29.23 MPa, the impact energy index of coal is 19.97, the average bulk density of the overlying strata is 0.025 MP / m, and the planned maximum mining depth of the mining face is 750 m.

[0035] Step S2: According to the formula The critical depth H of rock burst is calculated cr =1.262×29.23×(1+1 / 19.97) / 2 / 0.025=775m.

[0036] Step S3: Constructing a judgment matrix of factors affecting rock burst in the mine, which is specifically divided into the following steps:

[0037] (1) Taking into account the rock burst situation in the mine, the four factors were compared in pairs to obtain their importance to the rock burst, and the judgment matrix of each factor was constructed, as shown in Table 1.

[0038] Table 1 Judgment matrix of rock burst influencing factors

[0039] Factors affecting rock burst Coal seam factor 1 Geological structural factors 2 Impact Propensity Factor 3 Overburden factors 4 Coal seam factor 1 1 1 / 5 1 / 7 4 Geological structural factors 2 5 1 1 / 3 2 Impact Propensity Factor 3 7 3 1 1 / 5 Overburden factors 4 1 / 4 1 / 2 5 1

[0040] (2) Calculate the weight q of the impact factors of the mine rock burst. According to the formula, the weight value of coal seam factor q1 = 0.014, the weight value of geological structure factor q2 = 0.404, the weight value of impact tendency factor q3 = 0.508, and the weight value of overlying rock stratum factor q4 = 0.076 are calculated.

[0041] (3) Determine the value L of each influencing factor of the mine, and the value range of each factor is 0~1.

[0042] 1) As shown in Table 2, the coal seam factor is divided into three sub-factors and four-level indicators: coal seam thickness factor, coal seam inclination factor, and coal seam thickness variation factor. The coal seam thickness factor indicator is divided into thin coal seam, thick coal seam, medium-thick coal seam, and extra-thick coal seam; the coal seam inclination factor indicator is divided into nearly horizontal coal seam, gently inclined coal seam, inclined coal seam, and steeply inclined coal seam; the coal seam variation factor indicator is divided according to the variation range of coal seam thickness. Referring to the basic parameters of the average coal seam thickness of 6.5m, the average coal seam inclination of 3°, and the coal seam thickness variation coefficient of 0.22 in step S1, the coal seam factor = the coal seam thickness factor value of 0.22 + the coal seam inclination factor value of 0.00 + the coal thickness variation factor value of 0.11, and the coal seam factor value result L1 = 0.33.

[0043] Table 2 Coal seam factor indicators and values

[0044]

[0045] Note: For multi-coal seam mining, calculate the value of each coal layer separately and select the maximum value as L1; Coal thickness variation coefficient Where n is the total number of coal points, x i To see the coal point and measure the coal thickness, Average coal thickness.

[0046] 2) As shown in Table 3, the geological structure factor is divided into two sub-factors and four-level indicators: the complexity of the mine geological structure and the ratio of the stress increment caused by the structure to the normal stress value. The geological structure complexity index is divided into simple, medium, complex, and extremely complex, and the value is determined according to the conclusion of the mine geological description; the stress increment to normal stress value ratio index is divided into four levels, and the value is determined according to the conclusion of the mine ground stress test report and the bulk density of the overlying rock strata. In step S1, the mine geological structure complexity is medium, the maximum principal stress of the mine in the ground stress test is 31.2 MPa, the average bulk density of the overlying rock strata is 0.025 MP / m, and the planned maximum mining depth of the mining working face is 750 m. The basic parameters are as follows: the geological structure factor = the mine geological structure complexity value of 0.17 + the ratio of the stress increment caused by the structure to the normal stress value of 0.17, and the geological structure factor value result L2 = 0.34.

[0047] Table 3 Geological structural factor indicators and values

[0048]

[0049] Note: Mine geological complexity L 21 Select according to the mine geological description; P = (σ max -σ) / σ=(31.2-0.025×750) / (0.025×750)=0.64, where σ maxis the maximum principal stress, σ is the vertical stress, σ=γH, γ is the bulk density of the overlying rock.

[0050] 3) As shown in Table 4, the impact tendency factor L3 is divided into three sub-factors and three-level indicators: the impact tendency factor of coal, the impact tendency factor of roof rock strata, and the impact tendency factor of floor rock strata. The impact tendency of coal, roof rock strata, and floor rock strata are obtained through experiments in accordance with the national standards "Methods for the determination, monitoring and prevention of rock burst pressure - Part 1: Classification and determination method of roof rock burst tendency and index" (GB / T 25217.1) and "Methods for the determination, monitoring and prevention of rock burst pressure - Part 2: Classification and determination method of coal seam burst tendency and index" (GB / T 25217.2). In control step S1, the impact tendency of coal is strong impact tendency, the impact tendency of roof rock layer is weak impact tendency, and the bottom rock layer has no impact tendency basic parameters. The impact tendency factor = coal impact tendency factor 0.33 + roof rock layer impact tendency factor 0.17 + bottom rock layer impact tendency factor 0.00, and the impact tendency factor value is 0.50.

[0051] Table 4 Impact tendency factor indicators and values

[0052]

[0053] Note: For multi-seam mining, calculate the impact tendency factor score of each layer separately and select the maximum value as L3.

[0054] 4) As shown in Table 5, the overlying stratum factor L4 is divided into two sub-factors and four-level indicators: the characteristic parameter factor of the thickness of the roof rock layer above the coal seam and the distance factor of the hard thick rock layer in the overlying fracture zone from the coal seam. Among them, the characteristic parameter index of the thickness of the roof rock layer above the coal seam and the distance index of the hard thick rock layer in the overlying fracture zone from the coal seam are divided according to the thickness of the hard rock layer, and are obtained according to the comprehensive histogram of the mine and the geological drill hole histogram; referring to the basic parameters of the thickness characteristic parameter of the roof rock layer above the coal seam of 62m and the distance of the hard thick rock layer in the overlying fracture zone from the coal seam of 40m in step S1, the overlying stratum factor = the characteristic parameter factor of the thickness characteristic parameter of the roof rock layer above the coal seam 0.17 + the distance factor of the hard thick rock layer in the overlying fracture zone from the coal seam 0.33, and the overlying stratum factor value is 0.50.

[0055] Table 5 Overlying rock strata factor indicators and values

[0056]

[0057] Note: The calculation of overburden rock factor T is based on the mine comprehensive histogram and the mining situation of multiple coal seams. The overburden rock factor score of each coal layer is calculated separately, and the maximum value is selected as the T value. The characteristic parameter of the roof rock layer thickness above the coal seam is T = Σhi r i , h i is the thickness of the i-th rock layer above the roof, r i is the weak plane decline coefficient of the given rock formation. During the T calculation process, the mining influence range above the coal seam is selected, which should be no less than 100m.

[0058] (4) Calculate the equivalent depth of the mine. Based on the above data, the equivalent depth of the mine is calculated as follows: H = (1 + q1L1 + q2L2 + q3L3 + q4L4) × h = (1 + 0.014 × 0.33 + 0.404 × 0.34 + 0.508 × 0.50 + 0.076 × 0.50) × 750 = 1075m

[0059] Step S4: Determine whether the mine is a rock burst mine. The calculated equivalent depth is H = 1075m, and the critical depth for rock burst is 775m. cr Therefore, it is judged to be a rock burst mine.

[0060] Step S5: Determine the rock burst level of the mine. Rock burst mines are classified into three levels: weak rock burst mines, moderate rock burst mines, and strong rock burst mines. A mine with a rock burst level of 775m < equivalent depth H = 1075m ≤ 775 × 1.5m is considered weak.

[0061] For mines identified as having weak rock burst levels, they should be managed as weak rock burst mines during mine supervision, inspection, and on-site rock burst prevention and control. Coal mines should focus on monitoring and early warning based on rock burst hazard assessment and rock burst prevention design. When monitoring indicates danger, mitigation measures must be taken. At the same time, the superior departments of the coal mines should appropriately increase the frequency of supervision and inspection to ensure that no rock burst accidents occur in the coal mine.

[0062] The various sub-factors and their classification indicators, as well as the rock burst mine classification in the embodiments of the present invention, are for reference only. Practical applications are not limited to the above parameters. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for identifying and grading rock burst mines based on equivalent depth, characterized in that: The following steps are involved: Step 1: Parameter collection: Collect mine geological environment parameters; Step 2: Calculate the critical depth of rock burst: Calculate the critical depth H of rock burst according to formula (1): cr : Where, σ c is the uniaxial compressive strength of the coal body, in MPa; γ is the bulk density of the overlying rock, in MP / m; K E is the impact energy index of coal; η1 is the correction coefficient, Step 3: Calculate the equivalent depth H: Calculate the equivalent depth H according to formula (2): H=(1+q1L1+q2L2+q3L3+q4L4)×h (2) Wherein, h is the maximum depth of the mining face during the mine planning period, in meters; q1 is the weight of the coal seam factor; L1 is the value of the coal seam factor; q2 is the weight of the geological structure factor; L2 is the value of the geological structure factor; q3 is the weight of the impact tendency factor; L3 is the value of the impact tendency factor; q4 is the weight of the overburden factor; L4 is the value of the overburden factor; Step 4: Determine whether the mine is a rock burst mine: Substitute the equivalent depth H obtained in step 3 with the critical depth H of rock burst obtained in step 2. cr For comparison, when the mine equivalent depth H≥H cr When the mine is at a depth of H <H cr When , it is judged as a non-rock burst mine; Step 5: Identify the rock burst mine grade: When a mine is identified as a rock burst mine, the rock burst mine grade is divided into three levels: weak rock burst mine, medium rock burst mine, and strong rock burst mine; When H cr ≤H<1.5H cr When , it is judged to be a weak rock burst mine; When 1.5H cr ≤H<2H cr When the rock burst is detected, it is judged as a medium rock burst mine; When H≥2H cr When the mine is detected, it is judged to be a mine with strong rock burst.

2. The method for identifying and grading rock burst mines based on equivalent depth according to claim 1, characterized in that: The mine geological environment parameters described in step 1 include: the thickness, inclination and coefficient of variation of the coal seam factors in the mine, the complexity of the mine geological structure and the ratio of the stress increment to the normal stress value in the geological structure factors, the impact tendency results of the coal seam and the roof and floor plates in the impact tendency factors, the characteristic parameters of the thickness of the roof rock layer above the coal seam in the overburden rock layer factors, the distance parameters of the hard and thick rock layer in the fracture zone from the coal seam, as well as the uniaxial compressive strength of coal in each coal seam, the bulk density of the overburden rock layer, the impact energy index of the coal, and the mining depth of the mining face during the mine planning period.

3. The method for identifying and grading rock burst mines based on equivalent depth according to claim 1, characterized in that: The calculation process of the coal seam factor weight q1, geological structure factor weight q2, impact tendency factor weight q3, and overlying rock layer factor weight q4 in step 3 is as follows: ① Construct the judgment matrix of rock burst influencing factors: According to the rock burst situation of the mine, the four main control factors of the mine are compared pairwise to obtain the importance of the occurrence of rock burst in the mine, and the judgment matrix P of each factor is constructed. ij Formula (3): Among them, the right diagonal elements of the matrix P 12 It indicates the importance of coal seam factors compared with geological structure factors in determining mine rock burst; P 13 It indicates the importance of coal seam factors compared with the impact tendency factors in determining the impact rock pressure in the mine; P 14 P represents the importance of coal seam factors compared with overlying rock factors in determining mine rock burst; 23 It indicates the importance of geological structural factors compared with impact tendency factors in determining rock burst in mines; P 24 It indicates the importance of geological structure factors compared with overlying rock factors in determining mine rock burst; P 33 It indicates the importance of the impact tendency factor compared with the overburden factor in determining the rock burst in the mine. Similarly, the definition of the left diagonal elements of the matrix is opposite to that of the right diagonal elements, and its value is the reciprocal of the right diagonal value. P ij The value range of each element in the matrix is an integer between 1 and 9 or its reciprocal; 1 means that the two elements are equally important; 3 means that the former is slightly more important than the latter; 5 means that the former is significantly more important than the latter; 7 means that the former is strongly more important than the latter; 9 means that the former is extremely more important than the latter; other values represent the degree of importance between adjacent importance levels; similarly, the reciprocal of the integer between 1 and 9 represents the degree of importance of the latter over the former. ② Calculate the weight q of each influencing factor: Calculate the weight of the four factors as shown in formula (4); In the formula, i ranges from 1 to 4, corresponding to the coal seam factor weight value q1, the geological structure factor weight value q2, the impact tendency factor weight value q3 and the overlying rock stratum factor weight value q4.

4. The method for identifying and grading rock burst mines based on equivalent depth according to claim 1, characterized in that: In step 3, the coal seam factor value L1, the geological structure factor value L2, the impact tendency factor value L3, and the overburden stratum factor value L4 range from 0 to 1, and the value selection process is as follows: ① The coal seam factor is divided into three sub-factors: coal seam thickness factor, inclination factor, and coal seam thickness variation factor. The value range of the three sub-factor indicators is divided and compared with the actual situation of the mine to obtain the coal seam factor L m The result of the value selection is that the coal seam factor L1 = the coal seam thickness factor L 11 + Coal seam dip factor L 12 + Coal thickness variation factor L 13 ; ② The geological structure factor is divided into two sub-factors: the complexity of the mine geological structure and the ratio of the stress increment caused by the structure to the normal stress value. The value range of the two sub-factor indicators is divided, and the value result of the geological structure factor L2 is obtained by comparing it with the actual situation of the mine. The geological structure factor L2 = the complexity of the mine geological structure L 21 +Ratio of stress increment caused by construction to normal stress value L 22 ; ③ Impact tendency factor L3 is divided into three sub-factors: coal impact tendency factor, roof rock impact tendency factor, and floor rock impact tendency factor. The three sub-factor index value ranges are divided and compared with the actual situation of the mine to obtain the impact tendency factor value results. Impact tendency factor L3 = coal impact tendency factor L 31 + Roof rock impact tendency factor L 32 +Floor rock impact tendency factor L 33 ; ④ Overlying rock layer factor L4 is composed of two sub-factors: the characteristic parameter factor of the thickness of the roof rock layer above the coal seam and the distance factor of the hard thick rock layer in the overlying fracture zone from the coal seam. The value range of the two sub-factor indicators is divided and the overlying rock layer factor value result is obtained by comparing with the actual situation of the mine. Overlying rock layer factor L4 = characteristic parameter factor L of the thickness of the roof rock layer above the coal seam 41 +The distance factor L between the hard and thick rock layer in the overlying fracture zone and the coal seam 42 .

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