Surface movement and vibration prediction method for working face mining in mine with thick and hard rock strata

Abstract

The application discloses a kind of thick hard rock layer occurrence mine working face mining surface movement-vibration prediction method, comprising: mechanism analysis is carried out to the overlying high position thick hard rock fracture of stope, and elastic mechanics model is established;Analysis is carried out to the movement characteristics between multilayer rock strata;Establish the rock beam model before the initial breakage of roof strata, and determine the limit span of the initial breakage of roof strata;Analysis is carried out to the elastic energy accumulation and release law before and after the breakage of roof strata, and the elastic performance released by the initial and periodic breakage of roof strata is calculated, and the mine earthquake energy is estimated;Equivalent TNT explosive quantity is converted into mine earthquake energy, surface particle vibration velocity is calculated, mine earthquake intensity and damage degree to ground building are quantified;Concept definition and quantitative determination are carried out to the "moving circle" and "vibration circle" formed after the breakage of roof strata.The application discloses the mine earthquake mechanical mechanism and propagation law caused by the breakage of roof strata, and has important guidance to working face mining design and ground disaster prediction.

Description

Technical Field

[0001] This invention relates to the interdisciplinary fields of mining engineering and dynamic disaster prevention, specifically to a method for predicting surface movement and vibration in working faces of mines with thick, hard rock formations. Background Technology

[0002] The presence of hard, thick overlying rock strata is a common geological condition in producing mines, accounting for approximately 30% of all mines. Fracturing of these key rock strata can easily induce high-energy mine tremors and their secondary dynamic hazards, resulting in strong surface tremors and severe impacts (outbursts) at the working face, causing serious coal mine dynamic disasters. Due to the inherent characteristics of thick, hard rock strata—high strength, large thickness, wide impact range, underdeveloped joints and fissures, and significant distance from the coal seam—they can easily form large-area, hard, overhanging structures within the mining area, which are unlikely to collapse naturally in the short term.

[0003] Currently, there are no effective technologies for controlling, weakening, and treating high-altitude, thick, and hard rock strata in mining, mechanics, and other related fields. Mine earthquake prediction and early warning have become the main means of "earthquake resistance and disaster reduction." As the mining depth and intensity of such mines increase, and the surrounding environment becomes more complex, mine earthquakes and the secondary disasters they induce have become one of the major challenges affecting the safe and efficient mining of mines. Traditional mine earthquake prediction and early warning methods are insufficient to meet the accuracy requirements. Summary of the Invention

[0004] The present invention provides a more scientific and accurate method for predicting surface movement and vibration in mining faces with thick and hard rock strata, which can at least solve one of the above-mentioned technical problems.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for predicting surface movement and vibration in a working face of a mine with thick, hard rock strata includes the following steps: S1. Mechanism analysis of fractures in the high-lying, thick, hard rock overlying the mining area is conducted to deduce the stress field distribution and establish an elastic mechanical model. S2. Based on the elasticity model and the load influence of multiple overlying rock layers on the roof rock layer in the mining area, analyze the motion characteristics and load limits between the multiple rock layers. S3. Based on the characteristics of rock strata movement and load limit, analyze the stress characteristics of the top slab rock strata during the failure of a conventional deep beam structure, establish a rock beam model before the initial failure of the top slab rock strata, and determine the ultimate span of the initial failure of the top slab rock strata. S4. Based on the law of conservation of energy, analyze the accumulation and release of elastic energy before and after the fracture of the roof rock layer, introduce the energy ratio mechanism of bending elastic performance, calculate the elastic performance released by the initial and periodic fracture of the roof rock layer, and estimate the seismic energy. S5. Based on the characteristics of mine seismic energy attenuation, determine the energy conversion coefficient, convert the mine seismic energy into the equivalent amount of TNT explosive, introduce the blasting vibration research mechanism, calculate the vibration velocity of surface particles, and use it to quantify the intensity of mine seismic events and the degree of damage to ground buildings. S6. Define and quantitatively determine the "movement zone" and "vibration zone" formed after the top strata are fractured.

[0006] Furthermore, in S1, the "time-space" rupture events around the mining area mainly originate from the fracturing movement of the overlying strata, and the movement of the upper strata mainly originates from the horizontal stress rise caused by the fracture of the lower strata, which in turn leads to the sudden instability of the bearing structure. Assume the initial tensile stress of the high-lying, thick, hard rock mass is... s 0, the additional stress generated by the mutation is s a The ultimate tensile strength of rock strata or rock beams at fracture is [ s The mechanism by which sudden stress changes cause fractures in high-altitude, hard rock strata can be simplified as follows: s 0+ s a >[ s (1) Based on the theory of mine pressure, the stress and strain of the elastic rock beam increase slowly before instability. The thickness of the thick, hard rock layer is greater than the mining thickness of the coal seam, and the bending deflection is less than the mining thickness of the coal seam. Therefore, the bending deflection of the thick, hard rock layer is less than its own thickness. That is, the hard roof rock layer undergoes small elastic deformation before fracture. Therefore, assuming that the overlying rock load does not change significantly during the deformation of the roof rock layer, the rock beam before instability can be transformed into an elastic mechanical model of a beam with fixed ends under uniformly distributed load.

[0007] Furthermore, in S2, multiple thick and hard rock layers exist above the working face of the mine, covering the entire mining area. The movement and load mechanism of these multiple thick and hard rock layers affect the establishment of the dynamics model of the roof rock layer movement and the study of energy release laws. Based on the load method of rock beams in mining engineering, the cooperative movement characteristics of the multiple thick and hard rock layers are analyzed, considering the overlying... n The load on the influence of layered rock layers on thick, hard rock layers ( q n )1 is represented as: (2) in, h i Indicates the thickness of the i-th overlying rock layer. E i Indicates the overlay i The elastic modulus of the rock strata c i Indicates the overlay iThe unit weight of the rock strata i for n Index of rock strata; Calculate and compare the first based on equation (2). n Does it satisfy the condition when there is +1 layer? q n+1 )1<( q n )1, if so, then it means the first n The +1 rock layer no longer exerts a load on the thick, hard rock layer, i.e., the first rock layer, thus determining the load-bearing capacity of the rock layer.

[0008] Furthermore, in S3, considering the mechanical conditions of the hard and thick top rock layer, the stress characteristics of the top rock layer are different from those of conventional long beam structures. The initial fracture location is subjected to the compression of adjacent rock blocks. Assuming that the effect of the support layer at the beam support end is ignored, a stress characteristic model of the top rock layer during the fracture process of a conventional deep beam structure is established to obtain a simplified solid rock beam model. Based on this solid rock beam model, the limit span before the initial fracture of the hard top rock layer is analyzed. Taking the direction of the mine working face as a unit width, approximating a plane strain problem, based on Saint-Venant's principle, the stress function of the beam fixed at both ends is obtained as follows: (3) in, Represents the stress function. x and y These represent the lengths in the horizontal and vertical directions, respectively. A , B , C , D , P , F , S , Q and K They represent the undetermined coefficients; The stress function should satisfy the Laplace differential equation. Considering the boundary conditions of the solid rock beam model, the analytical expression for the stress field distribution of thick, hard rock layers under volume forces is obtained as follows: (4) in, This indicates the tensile stress in the horizontal direction of the fixed rock beam. This indicates the tensile stress in the vertical direction of the fixed rock beam. This indicates that the shear stress of the fixed rock beam is... c The unit weight of the rock strata, h For the thickness of the rock strata, l It is half the ultimate span of the rock strata; Based on the strength characteristics of the rock, it possesses: tensile strength. s <Shear strength t < compressive strengthR Therefore, the main failure mode of the top strata is tensile failure. Considering the characteristics of the bending moment distribution in the two-end fixed rock beams in mechanics of materials, as the span increases, the bending moment at the upper position embedded at both ends of the rock beam... x =± l , y =- h At point / 2, the negative bending moment is the largest, and the wire is the first to break. Therefore, the tensile stress at this location is calculated. s 1, that is, when x =± l , y =- h The tensile stress at / 2 is: (5) When the maximum tensile stress in a thick, hard rock stratum reaches its tensile strength, fractures occur. According to the maximum tensile stress strength theory in rock mechanics, the safe span for the top stratum to remain intact without fracture must meet the following condition: (6) in,[ s [This refers to] the ultimate tensile strength of thick, hard rock strata; This yields the ultimate breaking span. L S The calculation formula is: (7) The ultimate fracture span of each rock layer is calculated and compared based on equation (7).

[0009] Furthermore, in S4, complex energy transformations occur in the rock strata or rock beams during bending, fracturing, and movement. According to the law of conservation of energy, the energy released by the fracturing and instability of thick, hard rock strata is: U O = U I - U P - U C (8) in, U O The energy released by the fracturing and instability of thick, hard rock layers. U I This refers to the energy accumulated during the elastic deformation of thick, hard rock layers. U P This refers to the energy consumed by the rock mass during the deformation of thick, hard rock layers. U C The residual strain that remains after fracture; Taking the top strata at the time of the initial fracture as the research object, a stress and energy conservation analysis was performed on it. In this top strata... UI The energy includes the work done by the additional load from the overlying rock strata and the work done by its own weight during fracture and subsidence. U P Energy includes the energy consumed by plastic deformation and the energy consumed by shearing and friction due to objective joints during motion. Therefore, equation (8) is expressed as: U O = U q +U g －U s －U j －U c (9) in, U q The work done on the top strata by the additional load on the overlying strata. U g This represents the work done by the weight of the rock on the top strata during fracture. U s The energy consumed by the plastic deformation of the roof strata. U j Energy consumption due to objective joints in the top strata; Introducing a bending elastic energy proportion mechanism, the elastic energy released during the initial and periodic fracture of the roof strata is derived from the bulk elastic energy. U V Deformation elasticity U T and top plate bending elasticity U W Composition, the expression is: U O = U V + U T + U W (10) (11) (12) (13) in, m Poisson's ratio of the rock strata and rock mass. E The elastic modulus of the rock strata. c The density of the rock strata, H The depth of the rock strata G The shear elastic modulus of the rock strata. M Rock strata bending moment ,theThe angle at which the rock strata bend and subside; Therefore, the elastic properties released by the initial and periodic fractures of the top strata are calculated, where: Regarding the initial fracture elastic energy, we obtain: (14) Regarding the periodic fracture bending elastic energy, we obtain: (15) In the formula, q The equivalent load per unit length is the self-weight of the top stratum and the additional load of the overlying stratum. I The moment of inertia of the top strata is the cross section of the strata. L S The ultimate fracture span of the top stratum; Combining equations (14) and (15), we know that the bending elastic energy U W It is proportional to the fifth power of the ultimate fracture span of the top strata. L S The larger the value, the more energy is accumulated, thus satisfying the approximate equality condition of equation (16) in engineering: U O ≈ U W (16).

[0010] Furthermore, in S5, the seismic event causes vibration and disturbance to the surrounding rock mass. The seismic waves propagate in all directions from the source point, and the vibration is weaker the farther away from the source. The seismic waves can be regarded as plane waves. According to the attenuation law of seismic wave propagation, the relative decrease in wave energy is linearly related to the path traveled by the wave. Therefore, d U In the distance d x The change in energy is as follows: (17) in, U This refers to the energy generated by seismic activity in a mine. k The energy absorption coefficient of the medium; Integrating both sides, equation (17) becomes: U r =U O e -kx (18) in, U r This refers to the energy released from elasticity and converted into vibrational impact during mining operations. U O The seismic energy released from the fracture and instability of thick, hard rock layers; make or = e -kx Equation (18) is transformed into: U r ≈ theU O (19) in, or The energy conversion coefficient; Introducing Sadovsky's empirical formula to predict the maximum velocity of vibration: (20) in, v The peak vibrational velocity of the particle. Q This refers to the total amount of explosives used in a single detonation. r The spatial distance between the epicenter and ground facilities. a The particle vibration attenuation index; Taking the logarithm of both sides, equation (20) is transformed into: (twenty one) That is, on a logarithmic coordinate system, the dependent variable and independent variable A linear relationship exists. Is Intercept when =0 a This is the slope of the straight line; Introducing variables , and ,make , as well as Equation (21) is then transformed into a univariate linear regression equation: (twenty two) The vibration effect was estimated using an equivalent mass of elemental TNT explosive, and the relationship between the mine seismic energy and the equivalent amount of TNT explosive was established as follows: U r = Qq v (twenty three) in, q v There is a constant coefficient between the energy and mass of TNT explosives.

[0011] Furthermore, in S6, as the working face is mined and the exposed area of ​​the goaf increases, the overlying thick and hard rock layer undergoes fracture movement, forming a "moving circle" and a "vibration circle" on the surface of the mining area. The "moving circle" is formed by the subsidence of the rock layer around the surface of the mining area and is elliptical in shape. The "vibration circle" is formed by the mining vibration induced by the fracture of the thick and hard rock layer and transmitted to the surface, and is circular in shape. The formula for calculating the influence range of the "movement circle" and "seismic circle" on the Earth's surface after the fracture of thick, hard rock layers is as follows: (twenty four) in, D Z and D S These are the dip width and directional width of the Earth's surface "movement circle," respectively. L Z and L′ S These are the working face width and the pushing distance, respectively. H For coal seam burial depth, H L The vertical height of the thick, hard rock layer from the Earth's surface. α The angle of rock strata movement. r The spatial distance between the epicenter and ground facilities. r L This is the horizontal distance between the epicenter and ground facilities.

[0012] The beneficial effects of this invention are reflected in: 1. Based on the spatial structural laws of overburden, an elastic rock beam mechanical model with both ends fixed in a high-lying, thick, hard rock layer was established. Using the plane strain solution method and Saint-Venant's principle, an analytical formula for the stress field distribution of the hard, thick rock layer was derived, and a formula for calculating the fracture span of the hard, thick rock layer was obtained. Based on the tensile strength of the rock layer (stone)... s <Shear strength t < compressive strength R Based on the characteristics, a method for calculating the ultimate span of tensile failure in high-altitude, thick, and hard rock strata is proposed.

[0013] 2. Analyze the basic forms of energy accumulation and release after the unstable movement of high-altitude, thick, and hard rock strata, and derive the method for estimating the elastic energy accumulated during the initial fracture and periodic fracture of the hard roof strata and the energy converted from the seismic activity.

[0014] 3. Based on the methods of seismology and blasting science to calculate the vibration of rock mass particles around the earthquake source, the energy of the mine earthquake is converted into the equivalent mass of TNT explosives, and the method of blasting science to calculate the vibration velocity of particles is used to evaluate the intensity of the mine earthquake and the degree of damage to the external environment.

[0015] 4. Combining the laws of surface rock movement and mine seismic propagation, this paper explores the laws governing the fracture movement of key thick and hard rock strata induced by mining disturbance, which causes surface "movement" and "vibration," as well as simple calculation methods. Attached Figure Description

[0016] The accompanying drawings, which are provided to further illustrate this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0017] Figure 1 This is a distribution diagram of the initial pressure microseismic events at the overburden working face according to an embodiment of the present invention.

[0018] Figure 2 This is a distribution map of microseismic events at the initial exposure of the overburden working face according to an embodiment of the present invention.

[0019] Figure 3 This is a mechanical model diagram of the initial fracture of a high-level, thick, hard top rock stratum according to an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram illustrating the calculation of the elastic performance of a high-thickness, hard initial collapse according to an embodiment of the present invention.

[0021] Figure 5 This is a schematic diagram illustrating the calculation of elastic performance during high-density, hard, periodic collapse according to an embodiment of the present invention.

[0022] Figure 6 This is a diagram showing the energy distribution of the seismic source plane wave according to an embodiment of the present invention.

[0023] Figure 7 This is a schematic diagram illustrating the potential "movement" and "vibration" damage to the Earth's surface after a high-altitude, thick, and hard rock layer breaks.

[0024] Figure 8 This is a schematic diagram of the "movement circle" and "vibration circle" on the ground caused by mining in an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that the meaning of "and / or" throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, "multiple" refers to two or more. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0027] This invention provides a method for predicting surface movement and seismic activity in working faces of mines with thick, hard rock strata. Taking the high-lying, thick, hard rock strata of the 16101 working face in a Hebei mine as an example, based on the spatial structural characteristics of the overlying strata and the movement patterns of the rock strata, a mechanical model of a rock beam with fixed ends is established. This model yields a model of energy conversion and induced seismic activity during the fracture process of the high-lying, thick, hard rock strata, which has been verified in engineering practice, providing a theoretical basis for the prediction and prevention of seismic activity and secondary dynamic disasters. The specific implementation steps are as follows: Step 1: Obtain an overview of the actual project conditions.

[0028] A mine in Hebei Province is mining the No. 6 coal seam in the central part of the Taiyuan Formation. The coal is anthracite. The 16101 working face is the first working face in the mining area. It is located in front of the goaf in the north wing. The opening is far from the old goaf. The working face is 500m from the surface on average. The strike length is about 770m and the dip length is 150m. The average dip angle of the coal seam is 16° and the average thickness is 6m. The immediate roof is a 6.4m thick carbonaceous mudstone, and the old roof is a 13m thick composite rock stratum of silt and medium sand mudstone. The "strike longarm mining method" is adopted. The roof is managed by the fully mechanized longwall top coal caving method.

[0029] The strata exposed by boreholes and on the surface within the mining area, from oldest to youngest, are: the Mesoproterozoic Changcheng System Gaoyuzhuang Formation (Chg), the Mesoproterozoic Jixian System Wumishan Formation (Jxw), the Paleozoic Cambrian (∈), the Paleozoic Ordovician (O), the Paleozoic Carboniferous (C), the Mesozoic Jurassic (J), and the Cenozoic Quaternary (Q). The mining area is affected by a magmatic intrusion (CBI), and two thick, hard rock layers (igneous rock and limestone) cover the entire mining area above the No. 6 coal seam. The average thickness of the limestone roof of the No. 6 coal seam is 100m, with an average distance of 60m from the coal seam; the average thickness of the igneous rock roof of the No. 6 coal seam is 320m, with an average distance of 160m from the coal seam. Igneous rock directly lies above the limestone. The uniaxial tensile strengths of the limestone and igneous rock are 6.7MPa and 8.4MPa, respectively.

[0030] Step 2: Mechanism analysis of fractures in high-altitude, thick, and hard rock.

[0031] The essence of high-level, thick, hard rock fractures in the mining area: Mining of the working face causes horizontal stress concentration above the face. As the working face is further mined, the exposed area of ​​the goaf continuously increases, the fracture range of the overlying strata expands, and the vertical fracture height increases, causing the horizontal stress to rise continuously. This rising horizontal stress leads to abrupt stress changes in the bearing strata above. Based on the practical application of the field microseismic monitoring system, it is shown that the "time-space" (time T, energy J, coordinates) around the mining area... x , y , z Rupture events mainly originate from the fracturing of overlying strata, such as... Figure 1-Figure 2 As shown, the main reason for the movement of the high-level rock strata is the fracture of the lower rock strata, which causes the horizontal stress to rise and then leads to the sudden instability of the bearing structure.

[0032] Assume the initial tensile stress of the high-lying, thick, hard rock mass is... s 0, the additional stress generated by the mutation is s a The ultimate tensile strength of rock strata or rock beams at fracture is [ s The mechanism by which sudden stress changes cause fractures in high-altitude, hard rock strata can be simplified as follows: s 0+ s a >[ s (1) Based on the theory of mine pressure, the stress and strain of the elastic rock beam increase slowly before instability. The thickness of the thick, hard rock layer is generally greater than the mining thickness of the coal seam, and the bending deflection is much smaller than the mining thickness of the coal seam. Therefore, the bending deflection of the thick, hard rock layer is less than its own thickness. That is, the hard roof rock layer undergoes small elastic deformation before fracture. Therefore, assuming that the overlying rock load does not change significantly during the deformation of the roof rock layer, the rock beam before instability can be transformed into an elastic mechanical model of a beam with fixed ends under uniformly distributed load.

[0033] Step 3: Breaking distance of high-altitude, thick, hard rock layers.

[0034] Based on the conditions, the key layer above the working face mainly consists of two thick, hard rock layers, as shown in Table 1 below. Whether these two rock layers undergo delamination or form a composite roof with synchronous movement has a crucial impact on the subsequent establishment of the roof movement mechanical model and the study of energy release laws.

[0035] Table 1. Physical and mechanical parameters of rocks in key strata

[0036] The characteristics of the coordinated movement of two thick, hard rock layers were analyzed using the load-bearing method of rock beams in mining engineering, taking into account the overlying layers. n The loads on the influence of layered rock layers on the hard top layer ( qn )1 is represented as: (2) in, h i Indicates the thickness of the i-th overlying rock layer. E i Indicates the overlay i The elastic modulus of the rock strata c i Indicates the overlay i The unit weight of the rock strata i for n Index of rock strata.

[0037] The load borne by the independent movement of key layer 1 (limestone) is: (3) Assuming that key layer 2 (igneous rock) moves synchronously with key layer 1 (limestone), the load borne by key layer 1 (limestone) is: (4) because( q 2)1< q 1. This indicates that the lower limestone moves independently of the upper igneous rocks. Therefore, during the mining process, the first key layer of limestone, which is close to the coal seam, first undergoes delamination and fracture movement, and then the second key layer of igneous rocks, which is higher up, breaks when the overhang reaches the limit span.

[0038] Step 4: Model of the rock beam before the initial fracture.

[0039] The thin roof of the working face can collapse as mining progresses, and the composite roof is relatively close to the coal seam, allowing for normal collapse during mining. The high-lying, exposed, thick key strata possess physical characteristics such as hardness, integrity, and thickness, and can be approximated as a continuous medium in a mechanical calculation model. Since the ratio of the goaf size to the key strata thickness does not satisfy the assumptions of the elastic thin-plate mechanical model (the goaf size is 5-8 times or more the thickness of the roof strata), it is considered as an elastic rock beam structure supported on the coal seam or rock strata.

[0040] After the 16101 working face has been pushed forward a certain distance, a goaf area has been formed in space. From the strike profile, the high-lying, thick, hard rock strata are supported on one side of the goaf by boundary coal pillars and underlying rock strata, while on the other side they act on the coal face and overlying rock strata. From the dip profile, the angle of rock strata movement caused by mining is... α Low-lying rock strata along fracture angle β The fractures formed a series of fractures. The high-level, thick, hard rock strata were supported by the coal walls on both sides and the rock strata below them, while the middle strata were exposed due to the collapse and subsidence of the low-level rock strata.

[0041] Considering the hardness and thickness of the roof strata, the stress characteristics of the roof strata differ from those of conventional long beam structures. The initial fracture location is subjected to the compressive force of adjacent rock blocks. Assuming the effect of the support layer at the beam support end is ignored, a stress characteristic model of the roof strata during the fracture process of a conventional deep beam structure is established. (The model is then used in conjunction with other methods.) Figure 3 The simplified fixed-supported rock beam model shown is used to analyze the ultimate span before the initial fracture of the hard roof. c The unit weight of the rock strata (kN•m) -3 ), h The thickness of the rock strata (m) l It is half the ultimate span of the rock strata (m).

[0042] Step 5: Solving for the ultimate fracture span.

[0043] Taking the direction of the mine working face as a unit width, approximating a plane strain problem, based on Saint-Venant's principle, the stress function of the beam fixed at both ends is obtained as follows: (5) in, Represents the stress function. x and y These represent the lengths in the horizontal and vertical directions, respectively. A , B , C , D , P , F , S , Q and K They represent the undetermined coefficients; The stress function should satisfy the Laplace differential equation. Considering the boundary conditions of the solid rock beam model, the analytical expression for the stress field distribution of thick, hard rock layers under volume forces is obtained as follows: (6) in, This indicates the tensile stress in the horizontal direction of the fixed rock beam. This indicates the tensile stress in the vertical direction of the fixed rock beam. This indicates that the shear stress of the fixed rock beam is... c The unit weight of the rock strata, h For the thickness of the rock strata, l It is half the ultimate span of the rock strata; Based on the strength characteristics of the rock, it possesses: tensile strength. s <Shear strength t < compressive strength R Therefore, the main failure mode of the top strata is tensile failure. Based on the characteristics of bending moment distribution in a rock beam with fixed ends in mechanics of materials, as the span increases, the bending moment distribution at the upper position of the fixed ends of the rock beam... x =± l , y =- h At point / 2, the negative bending moment is the largest, and the wire is the first to break. Therefore, the tensile stress at this location is calculated. s 1, that is, when x =± l , y =- h The tensile stress at / 2 is: (7) When the maximum tensile stress in a thick, hard rock stratum reaches its tensile strength, fractures occur. According to the maximum tensile stress strength theory in rock mechanics, the safe span for the top stratum to remain intact without fracture must meet the following condition: (8) in,[ s [This refers to] the ultimate tensile strength of thick, hard rock strata; This yields the ultimate breaking span. L S The calculation formula is: (9) Substituting the physical and mechanical parameters of the key rock layer into equation (9), the ultimate fracture spans of limestone and igneous rocks were calculated as follows: L 1S =174m, L 2S =317m, meaning that the limestone fractured for the first time when the working face was pushed to the first single-square position during the mining process, and the higher igneous rocks began to fracture after the second single-square position.

[0044] Step 6: Energy conversion and elastic energy calculation for rock strata fracture.

[0045] Before and after the rock strata bend and stretch and break, there is a process of accumulation and release of elastic energy. During the process of roof breaking or sliding, a large amount of elastic energy is suddenly released, forming strong vibrations and inducing dynamic disasters such as mine tremors and shocks.

[0046] Rock strata or ridges undergo complex energy transformations during bending, fracturing, and movement. According to the law of conservation of energy, the energy released by the fracturing and instability of thick, hard rock strata is: U O = U I - U P - U C (10) in, U O The energy released by the fracturing and instability of thick, hard rock layers. U I This refers to the energy accumulated during the elastic deformation of thick, hard rock layers. U P This refers to the energy consumed by the rock mass during the deformation of thick, hard rock layers. U C The residual strain that remains after fracture.

[0047] Taking the top strata at the time of the initial fracture as the research object, a stress and energy conservation analysis was performed on it. In this top strata... U I The energy includes the work done by the additional load from the overlying rock strata and the work done by its own weight during fracture and subsidence. U P Energy includes the energy consumed by plastic deformation and the energy consumed by shearing and friction due to objective joints during motion. Therefore, equation (10) is expressed as: U O = U q +U g －U s －U j －U c (11) in, U q The work done on the top strata by the additional load on the overlying strata. U g This represents the work done by the weight of the rock on the top strata during fracture. U s The energy consumed by the plastic deformation of the roof strata. U j This refers to the energy consumption of objective joints in the roof strata.

[0048] Based on the above energy conversion calculation formulas, the actual calculation methods for the amount of energy accumulated and released before and after the fracture of the roof strata are relatively complex. According to Professor Avelshin's ideas, the elastic energy released by the initial and periodic fracture of the roof strata is composed of bulk elastic energy. U V Deformation elasticity U T and top plate bending elasticity U W Composition, the expression is: U O = U V+ U T + U W (12) (13) (14) (15) in, m Poisson's ratio of the rock strata and rock mass. E The elastic modulus of the rock strata. c The density of the rock strata, H The depth of the rock strata G The shear elastic modulus of the rock strata. M Rock strata bending moment ,the The angle at which the rock strata bend and sink.

[0049] Therefore, the elastic properties released by the initial and periodic fractures of the top strata are calculated, where: Regarding the initial fracture flexural elastic performance, such as Figure 4 As shown, we obtain: (16) Regarding the periodic fracture flexural elasticity, such as Figure 5 As shown, we obtain: (17) In the formula, q The equivalent load per unit length is the self-weight of the top stratum and the additional load of the overlying stratum. I The moment of inertia of the top strata is the cross section of the strata. L S It represents the ultimate fracture span of the top strata.

[0050] Combining equations (16) and (17), we know that the bending elastic energy U W It is proportional to the fifth power of the ultimate fracture span of the top strata. L S The larger the thickness, the more energy is accumulated. Meanwhile, according to Professor Avelshin's research, thick, hard rock layers have large fracture strides. U W It accounts for more than 90% of the total energy. Therefore, in engineering terms, the following equation can be satisfied: U O ≈ U W (18) During the mining process, the limestone (initial fracture step distance) L 1S =174m) and igneous rocks (initial fracture step distance) L2S The elastic energy released during the initial fracture of the 317m fracture was 1.12 × 10⁻⁶ m. 12 J and 1.88×10 13 J.

[0051] Step 7: Analyze the energy attenuation characteristics of mine seismic (vibration) events.

[0052] The energy that triggers mine earthquakes by fracturing thick, hard rock layers comes from the release of elastic energy. During the rock collision process, due to the energy consumption of the rock mass and the residual strain during deformation, most of the released energy is converted into heat energy.

[0053] like Figure 6 As shown, a seismic event causes disturbance in the medium surrounding the rock strata. Seismic waves propagate and radiate in all directions from the hypocenter. At a distance from the hypocenter, the seismic waves can be approximated as plane waves. According to the seismic wave propagation attenuation law, the relative decrease in wave energy is linearly related to the path traveled by the wave. Therefore, d... U In the distance d x The change in energy is as follows: (19) in, U This refers to the energy generated by seismic activity in a mine. k The energy absorption coefficient of the medium; Integrating both sides, equation (19) becomes: U r =U O e -kx (20) in, U r This refers to the energy released from elasticity and converted into vibrational impact during mining operations. U O The seismic energy released from the fracture and instability of thick, hard rock layers; make or = e -kx Equation (20) is transformed into: U r ≈ theU O (twenty one) in, or The energy conversion coefficient varies under different conditions. or The value range is only 1% to 40%, and generally no more than 50% of the energy is converted into mineral tremors.

[0054] It is evident that when thick, hard rock layers fracture, the released elastic energy and the converted vibrational energy are related to the thickness of the rock layer ( h), breaking step distance ( L S The vibration and impact energy generated around the strata are related to the vibration transmission distance and the initial energy that induces the mine tremor. U O ) and conversion coefficient or related.

[0055] Step 8: Study the particle vibration effect induced by the propagation of mine tremors (vibrations).

[0056] like Figure 7 As shown, the shock waves generated by the fracture of thick and hard rock layers cause vibration damage to the surrounding rock mass. The vibration effect is often characterized by the velocity of the particles, because the correlation between the vibration damage to the structure and the velocity of the particles is closer than that between displacement and acceleration.

[0057] Peak velocity is used as the unit for intensity and damage degree. When predicting the maximum vibration velocity, the Sadovsky empirical formula is introduced: (twenty two) in, v The peak vibrational velocity of the particle. Q This refers to the total amount of explosives used in a single detonation. r denoted as the distance from the explosion center, k is the medium coefficient, ranging from 50 to 250, which mainly depends on the properties of the medium through which the vibration wave propagates, and a is the particle vibration attenuation index, ranging from 1 to 2. Taking the logarithm of both sides, equation (22) is transformed into: (twenty three) That is, on a logarithmic coordinate system, the dependent variable and independent variable A linear relationship exists. Is Intercept when =0 a This is the slope of the straight line; Introducing variables , and ,make , as well as Equation (23) is then transformed into a univariate linear regression equation: (twenty four) According to Xie Yushou's observational research on the seismic effects of blasting, the vibration parameters k =200, a =1.8. Therefore, the maximum vibrational velocity of the particles produced by the vibration is... v and the amount of explosives Q ,distancer It can be approximated as: (25) If we take ground villages or buildings as the research object and limit the maximum allowable vibration velocity, the formula for calculating the safe distance from mine earthquakes is as follows: (26) In general, the fields of explosion science and seismology use the explosion of an equivalent mass of elemental TNT to estimate the vibration effects, and there is a constant between the estimated energy (J) and mass (kg). q v Therefore, the relationship between the seismic energy and the equivalent amount of TNT explosive is established as follows: U r = Qq v (27) Where, q v There is a constant coefficient between the energy and mass of TNT explosive, q v =4.2×106J / kg.

[0058] Step 9: Define the fractures in thick, hard rock layers and the “movement zone” and “vibration zone” on the Earth’s surface.

[0059] As the working face is mined and the exposed area of ​​the goaf increases, the thick, hard overlying rock strata are most prone to fracturing, forming "movement zones" and "vibration zones" on the surface of the mining area, such as... Figure 8 As shown, the "movement circle" is formed by the subsidence of the surrounding rock layers in the mining area and is elliptical in shape, while the "vibration circle" is formed by the transmission of mining tremors induced by the fracture of thick and hard rock layers to the surface and is circular in shape. The formula for calculating the influence range of the "movement circle" and "seismic circle" on the Earth's surface after the fracture of thick, hard rock layers is as follows: (28) in, D Z and D S These are the dip width and directional width of the Earth's surface "movement circle," respectively. L Z and L′ S These are the working face width and the pushing distance, respectively. H For coal seam burial depth, H L The vertical height of the thick, hard rock layer from the Earth's surface. α Let r be the angle of rock strata movement, and r be the spatial distance between the epicenter and ground facilities. r L This is the horizontal distance between the epicenter and ground facilities.

[0060] Step 10: Project verification.

[0061] The impact of mine seismic activity on the initial fracture of limestone and igneous rocks was calculated based on theoretical research. The energy conversion coefficient was used. or =20%, TNT pyrolysis constant coefficient q v =4.2×10 6 J / kg, rock strata displacement angle α =70°, and the parameters of the model pile and the prototype pile are obtained, as shown in Table 2 below.

[0062] Table 2. Parameter Table of Model Pile and Prototype Pile

[0063] During the actual mining operation of the 16101 working face, frequent mine-induced tremors occurred, which were felt on the surface. When the working face advanced to near the areas of the first and second single-cubic-meter breakthroughs, very strong mine-induced tremors occurred, with strong tremors felt on the surface. The mine-induced tremor during the second single-cubic-meter breakthrough caused relatively strong tremors to be felt by residents of a village approximately 1.1 km away from the 16101 working face (no damage to houses, and particle velocities between 1 and 3 cm / s). -1 An approximately elliptical "vibration zone" was formed on the surface, and "fracture" lines appeared. The "fracture" lines were about 150 to 200 meters away from the working boundary, indicating that the igneous rocks underwent fracture movement.

[0064] In summary, this invention addresses the inaccuracy of traditional mine seismic prediction and early warning methods by providing a method for predicting surface movement and vibration in working faces of mines with thick, hard rock strata. Specifically: (1) Based on the spatial structure law of overburden, an elastic rock beam mechanical model with both ends fixed in a high-altitude, thick, hard rock layer was established. Using the plane strain solution method and Saint-Venant's principle, the analytical formula for the stress field distribution of the hard, thick rock layer was derived, and the calculation formula for the fracture span of the hard, thick rock layer was obtained. Based on the tensile strength of the rock layer (stone) s <Shear strength t < compressive strength R Based on the characteristics, a method for calculating the ultimate span of tensile failure in high-altitude, thick, and hard rock strata is proposed.

[0065] (2) Analyze the basic forms of energy accumulation and release after the unstable movement of high-altitude, thick, hard rock strata, and derive the elastic energy accumulated by the initial fracture and periodic fracture of the hard roof and the energy estimation method of the transformation of the mine earthquake.

[0066] (3) Based on the method of calculating the vibration of rock mass particles around the earthquake source using seismology and blasting science, the earthquake energy is converted into the equivalent mass of TNT explosive, and the intensity of the earthquake and the degree of damage to the outside world are evaluated by using the method of calculating the vibration velocity of the particles using blasting science.

[0067] (4) Combining the laws of surface rock movement and mine seismic propagation, we explored the laws of mining disturbance inducing fracture movement of key hard rock strata, causing surface “movement” and “vibration”, as well as simple calculation methods.

[0068] (5) Based on the law of energy release and propagation of high-altitude thick hard rock strata fracture and mine earthquake, the mine earthquake induced by mining of the 16101 working face was verified, providing a basis for monitoring and early warning of dynamic disasters such as mine earthquake. It should be understood that the examples and embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various modifications or changes based on them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for predicting surface movement and vibration in a working face of a mine with thick, hard rock strata, characterized in that, Includes the following steps: S1. Mechanism analysis of fractures in the high-lying, thick, hard rock overlying the mining area is conducted to deduce the stress field distribution and establish an elastic mechanical model. S2. Based on the elasticity model and the load influence of multiple overlying rock layers on the roof rock layer in the mining area, analyze the motion characteristics and load limits between the multiple rock layers. S3. Based on the characteristics of rock strata movement and load limit, analyze the stress characteristics of the top slab rock strata during the failure of a conventional deep beam structure, establish a rock beam model before the initial failure of the top slab rock strata, and determine the ultimate span of the initial failure of the top slab rock strata. S4. Based on the law of conservation of energy, analyze the accumulation and release of elastic energy before and after the fracture of the roof rock layer, introduce the energy ratio mechanism of bending elastic performance, calculate the elastic performance released by the initial and periodic fracture of the roof rock layer, and estimate the seismic energy. S5. Based on the characteristics of mine seismic energy attenuation, determine the energy conversion coefficient, convert the mine seismic energy into the equivalent amount of TNT explosive, introduce the blasting vibration research mechanism, calculate the vibration velocity of surface particles, and use it to quantify the intensity of mine seismic events and the degree of damage to ground buildings. S6. Define and quantitatively determine the "movement zone" and "vibration zone" formed after the top strata are fractured.

2. The method for predicting surface movement and vibration in mining faces with thick, hard rock strata as described in claim 1, characterized in that, In S1, the "time-space" rupture events around the mining area mainly come from the fracturing movement of the overlying strata, and the movement of the upper strata mainly originates from the horizontal stress rise caused by the fracture of the lower strata, which in turn leads to the sudden instability of the bearing structure. Assume the initial tensile stress of the high-lying, thick, hard rock mass is... σ 0, the additional stress generated by the mutation is σ a The ultimate tensile strength of rock strata or rock beams at fracture is [ σ The mechanism by which sudden stress changes cause fractures in thick, hard rock strata at high elevations can be simplified as follows: σ 0+ σ a >[ σ ]（1） Based on the theory of mine pressure, the stress and strain of the elastic rock beam increase slowly before instability. The thickness of the thick and hard rock layer is greater than the mining thickness of the coal seam, and the bending deflection is less than the mining thickness of the coal seam. Therefore, the bending deflection of the thick and hard rock layer is less than its own thickness. That is, the thick and hard roof rock layer undergoes small elastic deformation before fracture. Therefore, assuming that the overlying rock load does not change significantly during the deformation of the roof rock layer, the rock beam before instability can be transformed into an elastic mechanical model of a beam with fixed ends under uniformly distributed load.

3. The method for predicting surface movement and vibration in mining faces with thick, hard rock strata as described in claim 1, characterized in that, In S2, multiple thick, hard rock layers exist above the working face, covering the entire mining area. The movement and loading mechanism of these multiple thick, hard rock layers affect the establishment of a dynamic model for the roof rock layer movement and the study of energy release laws. Based on the load method of rock beams in mining engineering, the cooperative movement characteristics of the multiple thick, hard rock layers are analyzed, considering the overlying... n The load on the influence of layered rock layers on thick, hard rock layers ( q n )1 is represented as: （2） in, h i Indicates the thickness of the i-th overlying rock layer. E i Indicates the overlay i The elastic modulus of the rock strata γ i Indicates the overlay i The unit weight of the rock strata i for n Index of rock strata; Calculate and compare the first based on equation (2). n Does it satisfy the condition when there is +1 layer? q n+1 )1<( q n )1, if so, then it means the first n The +1 rock layer no longer exerts a load on the thick, hard rock layer, i.e., the first rock layer, thus determining the load-bearing capacity of the rock layer.

4. The method for predicting surface movement and vibration in mining faces with thick, hard rock strata as described in claim 1, characterized in that, In S3, considering the mechanical conditions of the hard and thick top rock layer, the stress characteristics of the top rock layer are different from those of conventional long beam structures. The initial fracture location is subjected to the compression of adjacent rock blocks. Assuming that the effect of the support layer at the beam support end is ignored, a stress characteristic model of the top rock layer during the fracture process of a conventional deep beam structure is established to obtain a simplified solid rock beam model. Based on this solid rock beam model, the limit span before the initial fracture of the hard top rock layer is analyzed. Taking the direction of the mine working face as a unit width, approximating a plane strain problem, based on Saint-Venant's principle, the stress function of the beam fixed at both ends is obtained as follows: （3） in, Represents the stress function. x and y These represent the lengths in the horizontal and vertical directions, respectively. A , B , C , D , P , F , S , Q and K They represent the undetermined coefficients; The stress function should satisfy the Laplace differential equation. Considering the boundary conditions of the solid rock beam model, the analytical expression for the stress field distribution of thick, hard rock layers under volume forces is obtained as follows: （4） in, This indicates the tensile stress in the horizontal direction of the fixed rock beam. This indicates the tensile stress in the vertical direction of the fixed rock beam. This indicates that the shear stress of the fixed rock beam is... γ The unit weight of the rock strata, h For the thickness of the rock strata, l It is half the ultimate span of the rock strata; Based on the strength characteristics of the rock, it possesses: tensile strength. σ <Shear strength τ < compressive strength R Therefore, the main failure mode of the top strata is tensile failure. Considering the characteristics of the bending moment distribution in the two-end fixed rock beams in mechanics of materials, as the span increases, the bending moment at the upper position embedded at both ends of the rock beam... x =± l , y =- h At point / 2, the negative bending moment is the largest, and the wire is the first to break. Therefore, the tensile stress at this location is calculated. σ 1, that is, when x =± l , y =- h The tensile stress at / 2 is: （5） When the maximum tensile stress in a thick, hard rock stratum reaches its tensile strength, fractures occur. According to the maximum tensile stress strength theory in rock mechanics, the safe span for the top stratum to remain intact without fracture must meet the following condition: （6） in,[ σ [This refers to] the ultimate tensile strength of thick, hard rock strata; This yields the ultimate breaking span. L S The calculation formula is: （7） The ultimate fracture span of each rock layer is calculated and compared based on equation (7).

5. The method for predicting surface movement and vibration in mining faces with thick, hard rock strata as described in claim 1, characterized in that, In S4, complex energy transformations occur in the rock strata or rock beams during bending, fracturing, and movement. According to the law of conservation of energy, the energy released by the fracturing and instability of thick, hard rock strata is: U O = U I - U P - U C （8） in, U O The energy released by the fracturing and instability of thick, hard rock layers. U I This refers to the energy accumulated during the elastic deformation of thick, hard rock layers. U P This refers to the energy consumed by the rock mass during the deformation of thick, hard rock layers. U C The residual strain that remains after fracture; Taking the top strata at the time of the initial fracture as the research object, a stress and energy conservation analysis was performed on it. In this top strata... U I The energy includes the work done by the additional load from the overlying rock strata and the work done by its own weight during fracture and subsidence. U P Energy includes the energy consumed by plastic deformation and the energy consumed by shearing and friction due to objective joints during motion. Therefore, equation (8) is expressed as: U O = U q +U g －U s －U j －U c （9） in, U q The work done on the top strata by the additional load on the overlying strata. U g This represents the work done by the weight of the rock on the top strata during fracture. U s The energy consumed by the plastic deformation of the roof strata. U j Energy consumption due to objective joints in the top strata; Introducing a bending elastic energy proportion mechanism, the elastic energy released during the initial and periodic fracture of the roof strata is derived from the bulk elastic energy. U V Deformation elasticity U T and top plate bending elasticity U W Composition, the expression is: U O = U V + U T + U W （10） （11） （12） （13） in, μ Poisson's ratio of the rock strata and rock mass. E The elastic modulus of the rock strata. γ The density of the rock strata, H The depth of the rock strata G The shear elastic modulus of the rock strata. M Rock strata bending moment θ The angle at which the rock strata bend and subside; Therefore, the elastic properties released by the initial and periodic fractures of the top strata are calculated, where: Regarding the initial fracture elastic energy, we obtain: （14） Regarding the periodic fracture bending elastic energy, we obtain: （15） In the formula, q The equivalent load per unit length is the self-weight of the top stratum and the additional load of the overlying stratum. I The moment of inertia of the top strata is the cross section of the strata. L S The ultimate fracture span of the top stratum; Combining equations (14) and (15), we know that the bending elastic energy U W It is proportional to the fifth power of the ultimate fracture span of the top strata. L S The larger the value, the more energy is accumulated, thus satisfying the approximate equality condition of equation (16) in engineering: U O ≈ U W （16）。 6. The method for predicting surface movement and vibration in mining faces with thick, hard rock strata as described in claim 1, characterized in that, In S5, the seismic event causes vibration and disturbance to the surrounding rock mass. The seismic waves propagate in all directions from the source point, and the vibration weakens with distance from the source. The seismic waves can be considered as plane waves. According to the attenuation law of seismic wave propagation, the relative decrease in wave energy is linearly related to the path traveled by the wave. Therefore, d U In the distance d x The change in energy is as follows: （17） in, U This refers to the energy generated by mine seismic vibrations. k The energy absorption coefficient of the medium; Integrating both sides, equation (17) becomes: U r =U O e -kx （18） in, U r This indicates that elastic energy is released and converted into seismic vibration energy. U O The seismic energy released from the fracture and instability of thick, hard rock layers; make η = e -kx Equation (18) is transformed into: U r ≈ ηU O （19） in, η The energy conversion coefficient; Introducing Sadovsky's empirical formula to predict the maximum velocity of vibration: （20） in, v The peak vibrational velocity of the particle. Q This refers to the total amount of explosives used in a single detonation. r The spatial distance between the epicenter and ground facilities. a The particle vibration attenuation index; Taking the logarithm of both sides, equation (20) is transformed into: （21） That is, on a logarithmic coordinate system, the dependent variable and independent variable A linear relationship exists. Is Intercept when =0 a This is the slope of the straight line; Introducing variables , and ,make , as well as Equation (21) is then transformed into a univariate linear regression equation: （22） The vibration effect was estimated using an equivalent mass of elemental TNT explosive, and the relationship between the mine seismic energy and the equivalent amount of TNT explosive was established as follows: U r = Qq v （23） in, q v There is a constant coefficient between the energy and mass of TNT explosives.

7. The method for predicting surface movement and vibration in mining faces with thick, hard rock strata as described in claim 1, characterized in that, In S6, as the working face is mined and the exposed area of ​​the goaf increases, the overlying thick and hard rock layer undergoes fracture movement, forming a "moving circle" and a "vibration circle" on the surface of the mining area. The "moving circle" is formed by the subsidence of the rock layer around the surface of the mining area and is elliptical in shape. The "vibration circle" is formed by the mining vibration induced by the fracture of the thick and hard rock layer and transmitted to the surface, and is circular in shape. The formula for calculating the influence range of the "movement circle" and "seismic circle" on the Earth's surface after the fracture of thick, hard rock layers is as follows: （24） in, D Z and D S These are the dip width and directional width of the "movement circle" on the Earth's surface, respectively. L Z and L′ S These are the working face width and the pushing distance, respectively. H For coal seam burial depth, H L The vertical height of the thick, hard rock layer from the Earth's surface. α The angle of rock strata movement. r The spatial distance between the epicenter and ground facilities. r L This is the horizontal distance between the epicenter and ground facilities.

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