Method for identifying key stratum of mine earthquake

Abstract

The present application belongs to the technical field of coal mine earthquake and rock burst, and particularly relates to a mine earthquake key layer identification method, which comprises the following steps: S1: determining a working face to be analyzed; S2: determining a key layer position above a coal seam according to a rock stratum control key layer theory, and the number of key layers is denoted as m; wherein, n=0, E0=0; S3: n=n+1, from the bottom to the top of the coal seam, the bending energy index E of the nth key layer is calculated n ; S4: judging whether there is a free space below the nth key layer, if there is a free space, step five is entered, and if there is no free space, step six is entered; the present application can comprehensively consider factors such as rock stratum breakage, bending deformation energy, goaf range and "three zone" distribution, and can accurately determine the key layer position of a mine earthquake under different conditions in the process of coal seam mining.

Description

Technical Field

[0001] This invention belongs to the field of coal mine seismic and rockburst technology, specifically relating to a method for identifying key layers in seismic events. Background Technology

[0002] Mine tremors (hereinafter referred to as mine tremors) and rockbursts occur frequently in my country's major coal-producing areas. Mine tremors, also known as seismic events, generally refer to vibrations during coal seam mining that are felt or induce dynamic disasters in coal and rock. Rockbursts are sudden and violent destructive phenomena caused by the instantaneous release of elastic deformation energy in the coal (rock) mass surrounding mine tunnels or working faces, and mine tremors are one of the main causes of rockbursts. Therefore, controlling and mitigating the adverse effects of mine tremors has become an urgent issue for engineering sites and the scientific community to address in order to ensure the safe and efficient development of deep coal resources in my country.

[0003] A key rock stratum, or group of key strata, exists in the roof of a coal seam and plays a controlling role in the generation and distribution of mine-induced tremors; these are called the mine-induced tremor key strata. Faulting and slippage of the mine-induced tremor key strata are important causes of mine-induced tremors. Currently, methods for preventing mine-induced tremors and rockbursts mainly include underground deep-hole blasting, surface ultra-deep-hole blasting, underground hydraulic fracturing, and surface hydraulic fracturing. The primary task of these techniques is to accurately identify the target stratum (mine-induced tremor key stratum).

[0004] Among existing methods, empirical analogy lacks quantitative data support; numerical simulation methods are highly dependent on coal and rock constitutive properties and reasonable calculation step size; and theoretical models often only consider a specific geological and mining condition. Summary of the Invention

[0005] The purpose of this invention is to provide a method for identifying key seismic layers in coal seams, which can comprehensively consider factors such as rock strata fracture, bending deformation energy, goaf range, and the distribution of the "three zones" to accurately determine the location of key seismic layers in coal seam mining under different conditions.

[0006] The specific technical solution adopted by this invention is as follows:

[0007] A method for identifying key seismic layers in mines, comprising the following steps:

[0008] S1: Determine the working surface that needs to be analyzed;

[0009] When selecting borehole columnar sections, the selection criteria are that the borehole columnar sections are located within the working face or that the distance between the borehole columnar sections and the working face is small.

[0010] S2: Based on the theory of key strata control by rock strata, determine the key strata above the coal seam, and the number of key strata is denoted as m;

[0011] Let n = 0, then E0 = 0;

[0012] S3: Let n = n+1, and calculate the bending energy index E of the nth key layer from bottom to top of the coal seam. n ;

[0013] The calculation formula is:

[0014]

[0015] In the formula, E n R represents the bending energy index of the nth critical layer, in J. t-n h represents the tensile strength of the nth critical layer, in Pa. n q represents the thickness of the nth critical layer, in meters (m). n E represents the load per unit width of the nth critical layer, expressed in Pa. n Let be the elastic modulus of the nth critical layer, in Pa.

[0016] S4: Determine whether there is free space below the nth key layer. If there is free space, proceed to step five; otherwise, proceed to step six.

[0017] The judgment criteria are as follows:

[0018] H z =H c -H s ×ξ s

[0019] H c =H m +H v

[0020] In the formula, H z H represents the height of the free space below the nth critical layer, in meters. c The equivalent extraction height of the working face is expressed in meters (m); H m H represents the height of the coal seam at the working face, in meters (m). v The height of the immediate roof and follow-up collapse after the working face is mined, in meters (m); H s ξ represents the height of the breccia zone of the top strata, in meters; s The residual fragmentation coefficient of the top strata;

[0021] When H z When H is greater than 0, there is free space below the nth critical layer; when H z If the value is less than or equal to 0, then there is no free space below the nth key layer.

[0022] S5: Determine whether the nth critical layer will experience large-scale or even complete failure. If large-scale or even complete failure occurs, proceed to step seven; otherwise, proceed to step six.

[0023] The judgment criteria are as follows:

[0024]

[0025] In the formula, L w H represents the width of the goaf, in meters (m). coal H represents the coal seam burial depth, in meters (m). r The depth of the nth key stratum is given in meters (m); α is the fracture angle of the top stratum in degrees (°); h n R represents the thickness of the nth critical layer, in meters. t-n q represents the tensile strength of the nth critical layer, in Pa. n The load per unit width of the nth critical layer, expressed in Pa;

[0026] When L y When the value is greater than or equal to 0 and there is free space below the nth critical layer, the nth critical layer will have a large-scale or even complete breakage; in other cases, the nth critical layer will not have a large-scale breakage.

[0027] S6: The judgment result 1 is given: The nth key layer is located in the bending subsidence zone and will experience local fracture. It is a sub-seismic key layer.

[0028] S7: Based on the "three-hinged arch equilibrium" theory, determine whether the failure of the nth key layer will be located within the caving zone or the fracture zone; the judgment criterion is as follows:

[0029]

[0030]

[0031] In the formula, κ1 is coefficient 1; κ2 is coefficient 2; h n L represents the thickness of the nth critical layer, in meters (m). w Width of the goaf, in meters; η is the internal friction angle of the nth critical layer, in °; Δ is the free space below the critical layer, in m; η is the ratio of the compressive strength to the tensile strength of the rock block in the critical layer, taken as 8-12; K is the boundary condition coefficient, determined according to the fixed or simply supported state of the beam, and is 1 / 2-1 / 3; K′ is the ratio of the compressive strength to the compressive strength between the rock blocks in the critical layer.

[0032] When κ1 is less than or equal to 0 and κ2 is less than or equal to 0, the nth key layer is located within the fracture zone after fracture; otherwise, the nth key layer is located within the collapse zone after fracture.

[0033] S8: Determine the bending energy index E of the nth critical layer. nIs it greater than the bending energy index E of the (n-1)th critical layer? n-1 ;

[0034] In S8, if E n Greater than or equal to E n-1 Then the nth key layer is the main seismic key layer;

[0035] If E n Less than E n-1 Then the nth key layer is the sub-seismic key layer.

[0036] S9: Determine if n is less than m. If n is less than m, return to step four; if n is greater than or equal to m, the determination is complete, and the result is given.

[0037] The technical effects achieved by this invention are as follows:

[0038] The method for identifying key seismic strata in this invention is based on the theory of key strata control and the bending energy index of strata. It comprehensively considers factors such as strata fracture, bending deformation energy, goaf extent, and the distribution of the three zones of the roof, enabling accurate identification of key seismic strata in working faces under different geological and mining conditions. Furthermore, it proposes the concepts and discrimination methods for primary and sub-seismic key strata, providing a theoretical basis for determining target strata for seismic and rockburst prevention and control in coal mines. This significantly reduces the blind spots in engineering design, avoids huge waste of construction resources, and improves the scientificity and effectiveness of seismic and rockburst prevention and control, effectively ensuring the safe and efficient development of deep coal resources. Attached Figure Description

[0039] Figure 1 This is a flowchart of the method for identifying key layers in mine seismic activity according to an embodiment of the present invention;

[0040] Figure 2 This is a layer distribution diagram of the key layer in the fully mechanized longwall mining face according to Embodiment 08 of the present invention;

[0041] Figure 3 This is a stratigraphic map of the key seismic layer in the fully mechanized longwall mining face of Embodiment 08 of the present invention.

[0042] The attached diagram lists the components represented by each number as follows:

[0043] 1. Coal seam; 2. Sub-mineral seismic key layer-1; 3. Main mineral seismic key layer; 4. Sub-mineral seismic key layer-2; 5. Goaf; 6. Floor. Detailed Implementation

[0044] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0045] Example 1:

[0046] like Figures 1-3 As shown, the method for identifying key layers in mine seismic events includes the following steps:

[0047] S1: Determine the working surface that needs to be analyzed;

[0048] When selecting borehole columnar sections, the selection criteria are that the borehole columnar sections are located within the working face or that the distance between the borehole columnar sections and the working face is small.

[0049] S2: Based on the theory of key strata control by rock strata, determine the key strata above the coal seam, and the number of key strata is denoted as m;

[0050] Let n = 0, then E0 = 0;

[0051] S3: Let n = n+1, and calculate the bending energy index E of the nth key layer from bottom to top of the coal seam. n ;

[0052] The calculation formula is:

[0053]

[0054] In the formula, E n R represents the bending energy index of the nth critical layer, in J. t-n h represents the tensile strength of the nth critical layer, in Pa. n q represents the thickness of the nth critical layer, in meters (m). n E represents the load per unit width of the nth critical layer, expressed in Pa. n Let be the elastic modulus of the nth critical layer, in Pa.

[0055] S4: Determine whether there is free space below the nth key layer. If there is free space, proceed to step five; otherwise, proceed to step six.

[0056] The judgment criteria are as follows:

[0057] H z =H c -H s ×ξ s

[0058] H c =H m +H v

[0059] In the formula, H z H represents the height of the free space below the nth critical layer, in meters. cThe equivalent extraction height of the working face is expressed in meters (m); H m H represents the height of the coal seam at the working face, in meters (m). v The height of the immediate roof and follow-up collapse after the working face is mined, in meters (m); H s ξ represents the height of the breccia zone of the top strata, in meters; s The residual fragmentation coefficient of the top strata;

[0060] When H z When H is greater than 0, there is free space below the nth critical layer; when H z If the value is less than or equal to 0, then there is no free space below the nth key layer.

[0061] S5: Determine whether the nth critical layer will experience large-scale or even complete failure. If large-scale or even complete failure occurs, proceed to step seven; otherwise, proceed to step six.

[0062] The judgment criteria are as follows:

[0063]

[0064] In the formula, L w H represents the width of the goaf, in meters (m). coal H represents the coal seam burial depth, in meters (m). r The depth of the nth key stratum is given in meters (m); α is the fracture angle of the top stratum in degrees (°); h n R represents the thickness of the nth critical layer, in meters. t-n q represents the tensile strength of the nth critical layer, in Pa. n The load per unit width of the nth critical layer, expressed in Pa;

[0065] When L y When the value is greater than or equal to 0 and there is free space below the nth critical layer, the nth critical layer will have a large-scale or even complete breakage; in other cases, the nth critical layer will not have a large-scale breakage.

[0066] S6: The judgment result 1 is given: The nth key layer is located in the bending subsidence zone and will experience local fracture. It is a sub-seismic key layer.

[0067] S7: Based on the "three-hinged arch equilibrium" theory, determine whether the failure of the nth key layer will be located within the caving zone or the fracture zone; the judgment criterion is as follows:

[0068]

[0069] In the formula, κ1 is coefficient 1; κ2 is coefficient 2; h n L represents the thickness of the nth critical layer, in meters (m). wWidth of the goaf, in meters; η is the internal friction angle of the nth critical layer, in °; Δ is the free space below the critical layer, in m; η is the ratio of the compressive strength to the tensile strength of the rock block in the critical layer, taken as 8-12; K is the boundary condition coefficient, determined according to the fixed or simply supported state of the beam, and is 1 / 2-1 / 3; K′ is the ratio of the compressive strength to the compressive strength between the rock blocks in the critical layer.

[0070] When κ1 is less than or equal to 0 and κ2 is less than or equal to 0, the nth key layer is located within the fracture zone after fracture; otherwise, the nth key layer is located within the collapse zone after fracture.

[0071] S8: Determine the bending energy index E of the nth critical layer. n Is it greater than the bending energy index E of the (n-1)th critical layer? n-1 ;

[0072] In S8, if E n Greater than or equal to E n-1 Then the nth key layer is the main seismic key layer;

[0073] If E n Less than E n-1 Then the nth key layer is the sub-seismic key layer.

[0074] S9: Determine if n is less than m. If n is less than m, return to step four; if n is greater than or equal to m, the determination is complete, and the result is given.

[0075] Example 2:

[0076] The 08 fully mechanized longwall face in a certain mine is the second longwall face in the 221 mining area, with a goaf dipping width of 290m on one side. The 08 fully mechanized longwall face has a dipping length of 290m, and the average thickness of the mined 2-2 coal seam is 9.64m, with an equivalent mined body height of 12m. Based on the combined borehole columnar section and laboratory test results, the distribution of the roof strata and the physical and mechanical parameters of the working face are shown in Table 1.

[0077] Table 1. Distribution and physical and mechanical parameters of the roof strata in the 08 fully mechanized longwall face.

[0078]

[0079] Based on the theory of key strata controlling rock formations, the key strata positions of the 08 fully mechanized longwall mining face were determined, such as... Figure 2As shown, there are three key layers. The first key layer is fine-grained sandstone, 31.05m thick, located 0m from the coal seam; the second key layer is sandy mudstone, 41.2m thick, located 188.75m from the coal seam; and the third key layer is a sandstone group, 259.2m thick, located 357.45m from the coal seam. The load per unit width of the first key layer is 1214.355kPa; the load per unit width of the second key layer is 2424.548kPa; and the load per unit width of the third key layer is 6492.725kPa.

[0080] The bending energy index of each key layer was calculated from bottom to top of the coal seam. The results are as follows:

[0081]

[0082]

[0083] Determine whether there is free space below each key layer. The free spaces below the first, second, and third key layers are found to be 12m, 1.431m, and 0m, respectively, meaning there is no free space below the third key layer. According to the judgment criteria in step six, after the 08 fully mechanized longwall face is mined, the first and second key layers will experience large-scale or even complete fractures, while the third key layer will not experience large-scale fractures. According to the judgment criteria in steps seven and eight, after the first key layer fractures, it is located within the caving zone; after the second key layer fractures, it is located within the fracture zone; and after the third key layer fractures, it is located within the bending subsidence zone.

[0084] According to the process for identifying key seismic strata, the location of the key seismic strata after the mining of the 08 fully mechanized longwall face can be determined as follows: Figure 3 As shown, the first key layer is the sub-seismic key layer-1; the second key layer is the main seismic key layer; and the third key layer is the sub-seismic key layer-2.

[0085] Coal mine earthquakes and rock bursts have become major hazards encountered during coal mining. Pre-treatment of the hazard-causing rock strata is a fundamental approach to preventing and controlling these hazards. However, existing technologies suffer from limitations in accurately and completely locating these strata. The results of implementing this invention are as follows: Figure 3 As shown, the method for identifying key seismic layers proposed in this invention can accurately determine the main seismic key layers (primary disaster-causing rock layers) and sub-seismic key layers (secondary disaster-causing rock layers) during the mining process of the working face, thereby guiding the implementation of disaster control projects and improving the efficiency of prevention and control of coal mine seismic events and rockbursts.

[0086] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A method for identifying key layers in mine seismic activity, characterized by: The identification method includes the following steps: S1: Determine the working surface that needs to be analyzed; S2: Based on the theory of key strata control by rock strata, determine the key strata above the coal seam, and the number of key strata is denoted as m; Let n = 0, then E0 = 0; S3: Let n = n+1, and calculate the bending energy index E of the nth key layer from bottom to top of the coal seam. n ; S4: Determine if there is free space below the nth key layer. If free space exists, proceed to step five; otherwise, proceed to step six. The determination criterion is as follows: H z =H c -H s ×ξ s H c =H m +H v In the formula, H z H represents the height of the free space below the nth critical layer, in meters. c The equivalent extraction height of the working face is expressed in meters (m); H m H represents the height of the coal seam at the working face, in meters (m). v The height of the immediate roof and follow-up collapse after the working face is mined, in meters (m); H s ξ represents the height of the breccia zone of the top strata, in meters; s The residual fragmentation coefficient of the top strata; When H z When H is greater than 0, there is free space below the nth critical layer; when H z If the value is less than or equal to 0, then there is no free space below the nth key layer; S5: Determine whether the nth critical layer will experience large-scale or even complete failure. If large-scale or even complete failure occurs, proceed to step seven; if no large-scale failure occurs, proceed to step six. The judgment criteria are as follows: In the formula, L w H represents the width of the goaf, in meters (m). coal H represents the coal seam burial depth, in meters (m). r The depth of the nth key stratum is given in meters (m); α is the fracture angle of the top stratum in degrees (°); h n R represents the thickness of the nth critical layer, in meters. t-n q represents the tensile strength of the nth critical layer, in Pa. n The load per unit width of the nth critical layer, in Pa; When L y When the value is greater than or equal to 0 and there is free space below the nth critical layer, the nth critical layer may have a large-scale or even complete breakage; otherwise, the nth critical layer will not have a large-scale breakage. S6: The judgment result 1 is given: The nth key layer is located in the bending subsidence zone and will experience local fracture. It is a sub-seismic key layer. S7: Based on the "three-hinged arch equilibrium" theory, determine whether the failure of the nth key layer will be located within the caving zone or the fracture zone; the judgment criterion is as follows: In the formula, κ1 is coefficient 1; κ2 is coefficient 2; h n L represents the thickness of the nth critical layer, in meters (m). w Width of the goaf, in meters; η is the internal friction angle of the nth critical layer, in °; Δ is the free space below the critical layer, in m; η is the ratio of the compressive strength to the tensile strength of the rock block in the critical layer, taken as 8-12; K is the boundary condition coefficient, determined according to the fixed or simply supported state of the beam, and is 1 / 2-1 / 3; K′ is the ratio of the compressive strength to the compressive strength between the rock blocks in the critical layer. When κ1 is less than or equal to 0 and κ2 is less than or equal to 0, the nth key layer is located within the fracture zone after fracture; otherwise, the nth key layer is located within the collapse zone after fracture. S8: Determine the bending energy index E of the nth critical layer. n Is it greater than the bending energy index E of the (n-1)th critical layer? n-1 If E n Greater than or equal to E n-1 Then the nth key layer is the main seismic key layer; if E n Less than E n-1 Then the nth key layer is the sub-seismic key layer; S9: Determine if n is less than m.

2. The method for identifying key seismic layers according to claim 1, characterized in that: In step S1, a borehole columnar section is selected based on the principle that the borehole columnar section is located within the working surface or the distance between the borehole columnar section and the working surface is small.

3. The method for identifying key seismic layers according to claim 1, characterized in that: In step S9, if n is less than m, return to step four; if n is greater than or equal to m, the identification is complete and the result is given.

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