Method for judging influence of large-scale rhombus combined cantilever plate on mine earthquake

Abstract

The present application relates to the technical field of coal mine earthquake prediction, and particularly relates to a method for judging influence of large-scale rhombic combined cantilever plate on mine earthquake, which comprises the following steps: dividing the working face into two mining areas along the strike according to the coal seam thickness; performing key layer discrimination; calculating the thickness of the combined cantilever plate according to the height of the water flowing fractured zone; determining the position of the key layer in the combined cantilever plate, and simplifying the multiple rock layers controlled by each key layer into one soft rock group with consistent properties; calculating the fracture step distance of the combined cantilever plate; calculating the mine earthquake energy caused by the breakage of the combined cantilever plate; converting the mine earthquake energy into the Richter magnitude; and judging the influence on the mine earthquake. The present application can calculate the mine earthquake energy released when the combined cantilever plate breaks, so as to predict the mine earthquake grade induced by the breakage of the combined cantilever plate under the influence of mining. The mine can predict the mine earthquake grade according to the method, and take active and effective prevention measures according to the prediction, so as to ensure the safety production of the coal mine.

Description

Technical Field

[0001] This invention relates to the field of coal mine seismic prediction technology, specifically to a method for judging the impact of large-scale rhomboid combined cantilever plates on seismic activity. Background Technology

[0002] In some mines, mine tremors have become one of the most significant hazards. These tremors not only frequently interrupt and hinder daily production activities, leading to a sharp decline in production efficiency, but also pose a serious threat to the lives of mine workers. Furthermore, mine tremors can damage mine facilities and equipment, increasing economic losses, and in severe cases, even causing structural damage to the mine, increasing the risk of accidents. Therefore, mine tremors are not only a production obstacle but also a safety hazard that cannot be ignored.

[0003] However, effective prediction of mine tremors remains difficult due to the lack of accurate theoretical formulas for calculating their energy and magnitude. Energy and magnitude can only be obtained through monitoring instruments, which detect tremors only after they occur, making effective prediction impossible. Consequently, mines cannot implement targeted prevention and control measures. Although formulas for calculating the energy of mine tremors caused by key layer fractures have been proposed, they are difficult to apply to complex mining conditions, especially in mines with non-uniform thickness mining. Large-scale rhomboid composite cantilever plate structures may form above the stope. Due to their large size, these structures accumulate significant strain energy, and when they break during mining disturbances, they can easily trigger high-energy mine tremors, resulting in noticeable seismic responses both underground and on the surface, seriously threatening safe production. However, there is currently no research on calculating the energy of mine tremors caused by composite cantilever plate fractures. Summary of the Invention

[0004] To address the above problems, this invention proposes a method for assessing the impact of large-scale rhomboid composite cantilever plates on mine seismic activity. By calculating in advance the energy and magnitude of the seismic event caused by the failure of the composite cantilever plate, targeted measures for mine seismic disaster prevention can be formulated to ensure safe mine production. The method includes the following steps:

[0005] S1: The working face is divided into mining area A and mining area B along the strike. The average thickness of the coal seam in mining area A is m. a The average thickness of the coal seam in mining area B is m. b m a Greater than m b Coal seam recovery is carried out from mining area A to mining area B.

[0006] S2: Identify key layers in the overlying strata on the working face and determine the distribution of key layers in the overlying strata;

[0007] S3: Determine the height H of the water-conducting fracture development in mining area A.a And the height H of the water-conducting fractures in mining area B. b And calculate the thickness h of the combined cantilever plate according to formula (1);

[0008] h = H a -H b (1)

[0009] In the formula, h is the thickness of the composite cantilever plate, in meters (m); H a H represents the height of the water-conducting fractures in mining area A, in meters. b The height of the water-conducting fractures in mining area B, in meters;

[0010] S4: Determine the location of the key layers in the composite cantilever plate, and simplify the multiple rock layers controlled by each key layer into a soft rock layer group with consistent properties; determine the total number n of key layers and soft rock layer groups in the composite cantilever plate, as well as the elastic modulus, gravity density, tensile strength, and thickness parameters of each key layer and soft rock layer group;

[0011] S5: Calculate the fracture step L of the combined cantilever plate using formulas (2) and (3).

[0012]

[0013] In the formula, L is the fracture step distance (m) of the composite cantilever plate; R t q1 represents the tensile strength (Pa) of the lowest critical layer in the composite cantilever slab; q2 represents the load (N / m) borne by the lowest critical layer of the composite cantilever slab on the overlying rock strata within the composite cantilever slab. 2 E1 is the elastic modulus (Pa) of the lowest critical layer in the composite cantilever plate; E i h1 is the elastic modulus (Pa) of the i-th key layer or soft rock group from bottom to top in the composite cantilever plate; h1 is the thickness (m) of the lowest key layer in the composite cantilever plate; h i γi represents the thickness (m) of the i-th key layer or soft rock layer group from bottom to top in the composite cantilever plate; γ1 represents the gravity density (N / m2) of the lowest key layer in the composite cantilever plate. 3 );γ i The gravity density (N / m³) of the i-th key layer or soft rock group from bottom to top in the combined cantilever plate. 3 ); n is the total number of key layers and soft rock layers in the composite cantilever plate;

[0014] S6: Using formulas (4) to (8), calculate the seismic energy E caused by the failure of the combined cantilever plate.

[0015] E=η(E t +E g (4)

[0016]

[0017] In the formula, E is the seismic energy (J), and η is the conversion coefficient between elastic deformation energy and gravitational potential energy and seismic energy, typically taken as 0.26% to 3.6%. t The elastic deformation energy (J) released upon fracture of the combined cantilever plate; E g The gravitational potential energy (J) released by the combined cantilever plate during its rotation and sinking after fracture; q i The load (N / m) borne by the overlying rock strata in the composite cantilever slab, from bottom to top, on the i-th key layer or soft rock group in the composite cantilever slab. 2 b is the working face width (m); θ is the rotation angle of the combined cantilever plate after it breaks; ρ i The average density (kg / m³) of the i-th key layer or soft rock group from bottom to top in the combined cantilever plate. 3 g is the acceleration due to gravity (m / s²). 2 ); K P I is the residual breccia coefficient of the rock; i The moment of inertia (m) of the cross-section of the i-th key layer or soft rock layer group from bottom to top in the combined cantilever plate. 4 );m b The average thickness (m) of the coal seam in mining area B;

[0018] S7: Convert the seismic energy E calculated in step S6 into Richter magnitude M using formula (9). s

[0019] lgE = 1.9M s +1.8 (9)

[0020] S8: Determine the Richter magnitude M calculated in step S7. s Does M satisfy? s ≥1.7, if satisfied, the combined cantilever plate fracture has a significant impact on mine seismic activity.

[0021] The beneficial effects of the above-described technical solution of the present invention are as follows:

[0022] This invention can pre-calculate the seismic energy released when the combined cantilever plate breaks, thereby predicting the seismic intensity induced by the failure of the combined cantilever plate under mining influence. Mines can use this method to predict the seismic intensity and take proactive and effective prevention and control measures to ensure the safe production of coal mines. Attached Figure Description

[0023] Figure 1 This is a cross-sectional view of the coal seam strike in an example of the present invention;

[0024] Figure 2 This is a schematic diagram of the cantilever state of the large-scale rhomboid combined cantilever plate in an example of the present invention;

[0025] Figure 3 This is a schematic diagram of the fracture state of a large-scale rhomboid combined cantilever plate in an example of the present invention.

[0026] In the diagram, KS1 represents subcritical layer 1; KS2 represents subcritical layer 2; KS3 represents subcritical layer 3; and KS4 represents subcritical layer 4. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0028] This invention proposes a method for judging the impact of large-scale rhomboid composite cantilever plates on mine seismic activity, such as... Figure 1-3 As shown, the method includes the following steps:

[0029] S1: Collect borehole columnar data above the working face, and determine the lithology and thickness of the overlying rock layers based on the borehole columnar data, as shown in Table 1, which is one example of borehole columnar data; Figure 1-2 As shown, the thickness variation of the coal seam along the strike of the working face is determined by referring to the borehole column data. The working face is divided into mining area A and mining area B along the strike. The average thickness of the coal seam in mining area A is m. a The average thickness of the coal seam in mining area B is m. b And the average thickness of the coal seam in mining area A is m. a The average thickness of the coal seam in mining area B is significantly greater than that in m. b The coal seams in mining areas A and B are simplified to uniform thickness, and coal seams are mined from mining area A to mining area B.

[0030] In this embodiment, as Figure 1-2 As shown, the average thickness of the coal seam in mining area A is m. a =40m, the average thickness of the coal seam in mining area B is m b =20m.

[0031] S2: Identify key layers in the overlying strata on the working face to determine the distribution of key layers in the overlying strata. The results of the key layer identification are shown in Table 1. Figure 2 As shown;

[0032] Table 1. Borehole columnar data and key strata identification results

[0033]

[0034]

[0035] S3: Using the method of predicting the height of water-conducting fracture zones based on the location of key strata (Xu Jialin, Zhu Weibing, Wang Xiaozhen. Method for predicting the height of water-conducting fracture zones based on the location of key strata [J]. Journal of Coal Science and Technology, 2012, 37(5):762-769.), the height H of the water-conducting fracture development in the strata above mining area A is predicted. a And the height H of the water-conducting fractures in the rock strata above mining area B. b And calculate the combined cantilever plate thickness h formed due to non-uniform thickness mining according to formula (1);

[0036] h = H a -H b (1)

[0037] Where h is the thickness (m) of the composite cantilever plate; H a H represents the height (m) of the water-conducting fractures in the rock strata above mining area A; b The height (m) of the water-conducting fractures in the rock strata above mining area B;

[0038] Regarding the concept of combined cantilever plates, please refer to... Figure 2 As the coal seam thickness decreases during the transition from mining area A to mining area B, a difference in the height of the water-conducting fracture zone occurs at the transition point. This height difference forms a combination of several rock layers with a thickness of h, which exhibits a cantilever structure before fracturing. Subsequent calculations simplify this structure as a cantilever plate, hence the term "combined cantilever plate." Figure 3 As shown, when it breaks, it is approximately rhomboid in vertical cross-section, hence it is called a rhomboid composite cantilever plate.

[0039] In this embodiment, as shown in Table 1 and Figure 2 As shown, by determining the development height of water-conducting fractures in the overlying strata based on approximately 7 times the coal seam thickness and considering the location of key strata, the development height H of water-conducting fractures in mining area A can be obtained. a =279.25m, developed to the bottom interface of the subcritical layer 4; the height of the water-conducting fractures in mining area B is H. b =147.05m, developed to the bottom interface of the subcritical layer 2; substituting into formula (1), the thickness of the combined cantilever plate is h =132.2m.

[0040] S4: Determine the location of the key layers in the composite cantilever plate, and simplify the multiple rock layers controlled by each key layer into a soft rock layer group with consistent properties; determine the total number n of key layers and soft rock layer groups in the composite cantilever plate, as well as the elastic modulus, gravity density, tensile strength, and thickness parameters of each key layer and soft rock layer group;

[0041] In this embodiment, as Figure 2-3As shown, the composite cantilever plate has two key layers, namely sub-key layer 2 and sub-key layer 3. The rock strata controlled by sub-key layer 2 are the rock strata between sub-key layer 2 and sub-key layer 3, which are simplified into a soft rock stratum group with consistent properties. The rock strata controlled by sub-key layer 3 are the rock strata between sub-key layer 3 and sub-key layer 4, which are simplified into a soft rock stratum group with consistent properties. Therefore, the total number of key layers and soft rock stratum groups in the composite cantilever plate is n = 4. The simplification is for the purpose of facilitating calculation. The focus is on analyzing the key layers that control the movement of rock strata. In this embodiment of the invention, the elastic modulus, gravity density, tensile strength, and thickness parameters of each key layer and soft rock stratum group are shown in Table 2.

[0042] Table 2 Distribution and Corresponding Parameters of Combined Cantilever Slate Layers

[0043] Serial Number Rock strata distribution Thickness / m Elastic modulus / GPa Gravitational density (N / m3) Tensile strength / MPa 4 soft rock formation 24.7 21 13000 4 3 Subcritical layer 3 14.8 24 15000 7 2 soft rock formation 62.2 23 13000 6 1 Subcritical layer 2 30.5 25 25000 14

[0044] S5: As the working face advances in mining area B, the exposed length of the combined cantilever plate gradually increases. When the ultimate exposed span is reached, the combined cantilever plate breaks along its front end, as shown below. Figure 2 and Figure 3 As shown; the fracture step L of the combined cantilever plate is calculated using formulas (2) and (3);

[0045]

[0046]

[0047] In the formula, L is the fracture step distance (m) of the composite cantilever plate; R t q1 represents the tensile strength (Pa) of the lowest critical layer in the composite cantilever slab; q2 represents the load (N / m) borne by the lowest critical layer of the composite cantilever slab on the overlying rock strata within the composite cantilever slab. 2 E1 is the elastic modulus (Pa) of the lowest critical layer in the composite cantilever plate; E i h1 is the elastic modulus (Pa) of the i-th key layer or soft rock group from bottom to top in the composite cantilever plate; h1 is the thickness (m) of the lowest key layer in the composite cantilever plate; h i γi represents the thickness (m) of the i-th key layer or soft rock layer group from bottom to top in the composite cantilever plate; γ1 represents the gravity density (N / m2) of the lowest key layer in the composite cantilever plate. 3 );γ i The gravity density (N / m³) of the i-th key layer or soft rock group from bottom to top in the combined cantilever plate. 3 ); n is the total number of key layers and soft rock layers in the composite cantilever plate;

[0048] In this embodiment, the parameters of the key layer and soft rock layer group in the composite cantilever plate in Table 2 are substituted into formula (3) to calculate the load q1 = 225904.971 N / m borne by the overlying rock layer on the lowest key layer of the composite cantilever plate. 2 ; q1 = 225904.971 N / m 2 R t Substituting 14 MPa into formula (2), the fracture step distance L of the combined cantilever plate is calculated to be 138.6 m.

[0049] S6: Calculate the seismic energy E caused by the failure of the combined cantilever plate according to the seismic energy calculation formulas (4) to (8):

[0050] E=η(E t +E g (4)

[0051]

[0052] In the formula, E is the seismic energy (J), and η is the conversion coefficient between elastic deformation energy and gravitational potential energy and seismic energy, which is generally taken as 0.26% to 3.6%. Here, it is taken as 0.26% for calculation; E t The elastic deformation energy (J) released upon fracture of the combined cantilever plate; E g The gravitational potential energy (J) released by the combined cantilever plate during its rotation and sinking after fracture; q i The load (N / m) borne by the overlying rock strata in the composite cantilever slab, from bottom to top, on the i-th key layer or soft rock group in the composite cantilever slab. 2 b is the working face width (m); θ is the rotation angle of the combined cantilever plate after it breaks; ρ i The average density (kg / m³) of the i-th key layer or soft rock group from bottom to top in the combined cantilever plate. 3 g is the acceleration due to gravity (m / s²). 2 ); K P I is the residual fragmentation coefficient of the rock, which is taken as 1.11 here; i The moment of inertia (m) of the cross-section of the i-th key layer or soft rock layer group from bottom to top in the combined cantilever plate. 4 ).

[0053] In this embodiment, the elastic deformation energy and gravitational potential energy released by the fracture of each rock layer of the combined cantilever plate are calculated using formulas (5) to (8). The working face width b is taken as 100m and substituted into the calculation. The calculation results are shown in Table 3.

[0054] Table 3. Elastic deformation energy and gravitational potential energy released by the fracture of each rock layer in the combined cantilever plate.

[0055] Serial Number rock strata Elastic deformation energy / J Gravitational potential energy / J 4 soft rock formation 246258765.1 8511477975 3 Subcritical layer 3 60544701.6 5884609500 2 soft rock formation 4307053152 21433762350 1 Subcritical layer 2 551974856.6 20211778125

[0056] The elastic deformation energy and gravitational potential energy released by the fracture of each rock layer are summed to obtain the total elastic deformation energy E released by the fracture of the combined cantilever plate. t =5165831475J and total gravitational potential energy E g =56041627950J, substituting into formula (4), the vibration energy caused by the failure of the combined cantilever plate is calculated to be E=159139394.505J.

[0057] S7: Convert the seismic energy E calculated in step S6 into Richter magnitude M using formula (9). s

[0058] lgE = 1.9M s +1.8 (9)

[0059] In this embodiment, the Richter magnitude of the mine earthquake caused by the failure of the combined cantilever plate is calculated to be 3.37 using formula (9).

[0060] S8: Determine the Richter magnitude M calculated in step S7. s Does M satisfy? s ≥1.7, if satisfied, the combined cantilever plate fracture has a significant impact on mine seismic activity.

[0061] In this embodiment, the Richter magnitude M of the mine earthquake caused by the failure of the combined cantilever plate is... s =3.37>1.7, indicating that the failure of the combined cantilever plate has a significant impact on mine vibration, and the mine vibration caused by the failure is likely to trigger strong vibration reactions underground and on the surface, which can seriously threaten the safe production of the mine.

Claims

1. A method for judging the influence of large-scale rhombic combined cantilever plates on mine earthquakes, characterized in that, The method comprises the following steps: S1: dividing the working face along the strike into an A mining area and a B mining area, the average thickness of the coal seam in the A mining area being greater than the average thickness of the coal seam in the B mining area; and mining the coal seam from the A mining area to the B mining area; S2: discriminating a key layer in the overburden strata of the working face to determine the distribution of the key layer in the overburden strata; S3: Determine the water-conducting fracture development height H of the A mining area a and the water-conducting fracture development height H of the B mining area b and calculate the combined cantilever plate thickness h according to formula (1); h = H a -H b (1) In the formula, h is the thickness of the combined cantilever plate, m; H a is the height of the water-conducting fracture development in the A mining area, m; H b is the height of the water-conducting fracture development in the B mining area, m S4: determining the position of the key layer in the combined cantilever plate, and simplifying the multiple strata controlled by each key layer into one soft rock group with consistent properties; determining the total number n of the key layer and the soft rock group in the combined cantilever plate, and the elastic modulus, gravity density, tensile strength and thickness parameters of each key layer and soft rock group; S5: calculating the fracture step distance L of the combined cantilever plate by using formulas (2) and (3) In the formula, L is the fracture step distance of the combined cantilever plate, m; R t is the tensile strength of the lowermost key layer in the combined cantilever plate, Pa; q1 is the load borne by the lowermost key layer in the combined cantilever plate from the overlying strata of the combined cantilever plate, N / m 2 ; E1 is the elastic modulus of the lowermost key layer in the combined cantilever plate, Pa; E i is the elastic modulus of the i-th key layer or soft rock group from bottom to top in the combined cantilever plate, Pa; h1 is the thickness of the lowermost key layer in the combined cantilever plate, m; h i is the thickness of the i-th key layer or soft rock group from bottom to top in the combined cantilever plate, m; γ1 is the gravity density of the lowermost key layer in the combined cantilever plate, N / m 3 ; gamma i G is the gravity density of the i-th key layer or soft rock layer group from bottom to top in the composite cantilever slab, N / m 3 n is the total number of key layers and soft rock layer groups in the composite cantilever slab S6: calculating the mine earthquake energy E caused by the breakage of the combined cantilever plate by using formulas (4)-(8) E = η(E t + E g ) (4) wherein E is the mine shock energy, J, η is the conversion coefficient of elastic deformation energy and gravity potential energy into shock energy, and is taken as 0.26% to 3.6%; E t is the elastic deformation energy released by the breaking of the combined cantilever slab, J; E g is the gravity potential energy released by the rotation and subsidence after the breaking of the combined cantilever slab, J; q i is the load of the overlying strata in the combined cantilever slab borne by the i-th key stratum or soft rock stratum group from bottom to top, N / m 2 ; b is the working face width, m; θ is the rotation angle after the breaking of the combined cantilever slab; ρ i is the average density of the i-th key stratum or soft rock stratum group from bottom to top in the combined cantilever slab, kg / m 3 ; g is the gravity acceleration, m / s 2 ; K P is the residual dilatancy coefficient of the rock; I i is the cross-sectional moment of inertia of the i-th key stratum or soft rock stratum group from bottom to top in the combined cantilever slab, m 4 ; m b B is the average thickness of the coal seam in the mining area, m; S7: Convert the mine shock energy E calculated in step S6 into the Richter magnitude M by formula (9) s lgE = 1.9 M s +1.8 (9) S8: judging whether the calculated local magnitude M s whether M s ≥ 1.7, if yes, the combined cantilever plate breaking has a significant impact on mine earthquake.

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