Method and system for evaluating influence of working face mining on adjacent large fault stability

Abstract

The invention discloses a method and system for evaluating the influence of working face mining on adjacent large fault stability, and belongs to the field of coal mine safety mining. The method for evaluating the influence of working face mining on the stability of the adjacent large fault comprises the steps that a goaf-protective coal pillar-fault overburden strata space structure model is constructed, and external bearing stress borne by the protective coal pillar after working face mining is conducted is classified; comprise self-weight stress, lateral bearing stress transferred by overlying strata in a goaf and fault concentrated stress formed by a large fault; quantitative analysis is carried out on the lateral bearing stress of the goaf and the fault concentrated stress, and the average external bearing stress borne by the protective coal pillar after the working face is mined out is calculated; carrying out quantitative analysis on the internal bearing strength of the protective coal pillar, and calculating the average value of the internal bearing strength of the protective coal pillar; and evaluating the stability of the protective coal pillar based on the average external bearing stress borne by the protective coal pillar after the working face is mined out and the average value of the internal bearing strength of the protective coal pillar.

Description

Technical Field

[0001] The invention belongs to the field of safe mining of coal mines, and in particular relates to an evaluation method and system for the impact of working face mining on the stability of adjacent large faults. Background Art

[0002] In recent years, in order to maintain the "demand-supply" balance of coal resources, the intensity of coal mining has been continuously increased. However, due to the gradual depletion of shallow and easy-to-mine resources in the early stage, the next step will continue to face the problem of deep and complex coal mining conditions, such as the presence of fault structures in the mined coal seams. Faults are a common geological structure that can play a "controlling" role in coal seam mining design and safe mining. Under normal circumstances, the greater the fall and the closer the distance of the fault adjacent to the working face (or mining area), the more significant the impact on the mining of the working face, and often different degrees of mining fault instability (activation, movement, etc.) effects can be formed. Therefore, faults, as the main controlling factors that induce strong dynamic disasters such as rock burst, coal and gas outbursts, and roof water inrush, need to be evaluated in the pre-mining design stage to provide a basis for the implementation of necessary control in the later stage. At present, there is no technical means that can completely and effectively prevent and control the instability of mining-induced faults. The main engineering methods adopted are a combination of "assessment + prevention" before the working face is mined and "monitoring + control" during the working face is mined. "Monitoring + control" during the working face is often used. Microseismic monitoring of mines and fault grouting reinforcement management are passive means. "Assessment + prevention" before the working face is mined is an active means. What kind of assessment model and its adaptive prevention method to adopt has long been a problem that has plagued production units and scientific researchers. Summary of the invention

[0003] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method and system for evaluating the impact of working face mining on the stability of adjacent large faults, thereby solving the problems in the prior art.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] The method for evaluating the impact of working face mining on the stability of adjacent large faults includes the following steps:

[0006] A spatial structural model of goaf-protective coal pillar-fault overburden was constructed to classify the external support stress on the protective coal pillar after the working face was mined, including self-weight stress, lateral support stress transferred from the goaf overburden, and fault concentration stress formed by large faults.

[0007] Quantitatively analyze the lateral support stress and fault concentration stress in the goaf area, and calculate the average external support stress of the protective coal pillar after the working face is goafed;

[0008] Conduct quantitative analysis on the internal bearing strength of the protective coal pillar and calculate the average value of the internal bearing strength of the protective coal pillar;

[0009] The stability of the protective coal pillar is evaluated based on the average external support stress of the protective coal pillar after the working face is mined and the average internal bearing strength of the protective coal pillar.

[0010] Further, the steps of calculating the average external support stress of the protective coal pillar after the working face is mined include:

[0011] S21, quantitative analysis of lateral support stress in goaf;

[0012] S22, quantitative analysis of fault concentrated stress;

[0013] S23, determine the external support stress on the protective coal pillar after the working face is mined out, and calculate the average external support stress on the protective coal pillar after the working face is mined out.

[0014] Furthermore, the calculation formula of the lateral support stress σ′ of the goaf is:

[0015] σ′=Δσ+σ q

[0016]

[0017]

[0018] Where Δσ is the stress increment, Δσ=Σσ i ; σ i is the pressure transmitted from the exposed part of the i-th key layer to the coal body on one side, i = 1~n; σ q is the self-weight stress; σ maxi is the maximum bearing pressure of the i-th key layer on the coal body on one side of the goaf, σ maxi =Q i / H i cotα; α is the overburden movement angle, M i is the thickness of the i-th key layer; H i is the distance from the thickness center of the i-th key layer to the bottom of the coal seam, H i =h+M i / 2+ΣM j (j=1~i-1); L is the width of the goaf; Q i is half of the weight of the exposed part of the i-th key layer in the goaf, Q i =L i M i γ / 2; L i is the overhang length of the center position of the thickness of the i-th key layer in the goaf, L i =L+2H i cotα; γ is the bulk density of the rock layer; the stress increment Δσ generated by the exposed part of n key layersi Superposition is performed to obtain the stress increment Δσ; H is the mining depth, and h is the height of the lower rock layer of the working face from the coal seam.

[0019] Furthermore, the calculation formula of fault concentration stress σ″ is:

[0020]

[0021] Among them, a is the unilateral influence range, and k is the fault concentration stress coefficient.

[0022] Furthermore, the external support stress σ of the protective coal pillar after the working face is mined is:

[0023] σ=σ′+σ″

[0024] Average external support stress of the protective coal pillar after the working face is mined for:

[0025]

[0026] Where D is the width of the protective coal pillar, They are the average values ​​of lateral support stress in goaf and fault concentration stress respectively.

[0027] Furthermore, the calculation formula for the average value R of the internal bearing strength of the protective coal pillar is:

[0028]

[0029] Where [σ] is the uniaxial compressive strength of the coal body, t is the width of the elastic zone of the coal pillar, and ρ is the width of the plastic zone on one side of the coal pillar. b is the coal seam mining height, δ is the coal wall side pressure coefficient, is the friction angle inside the coal body, c is the cohesion inside the coal body, f is the friction coefficient between the top and bottom plates and the coal seam contact surface, It is the internal friction angle between the contact surface between the roof and floor plates and the coal seam.

[0030] Furthermore, when evaluating the stability of the protective coal pillar, I C To quantitatively characterize the feasibility index of protecting the overall instability of the coal pillar:

[0031]

[0032] in, is the average external support stress of the protective coal pillar after the working face is mined, and R is the average internal bearing strength of the protective coal pillar; I C The larger the value, the more feasible it is to protect the coal pillar from overall impact. C <1.0, the overall protection coal pillar remains stable; 1.0≤I C <1.5, protect the overall weak impact of coal pillar; 1.5≤IC <2.0, moderate impact on the overall protection coal pillar; 2.0≤I C , protecting the coal pillar from strong impact as a whole.

[0033] The assessment system for the impact of working face mining on the stability of adjacent large faults includes:

[0034] Spatial structure model construction module: Construct goaf-protective coal pillar-fault overburden spatial structure model, and classify the external support stress of the protective coal pillar after the working face is goafed, including: self-weight stress, lateral support stress transferred from the goaf overburden, and fault concentration stress formed by large faults;

[0035] External support stress calculation module: quantitatively analyze the lateral support stress and fault concentration stress of the goaf area, and calculate the average external support stress of the protective coal pillar after the working face is goafed;

[0036] Internal bearing strength calculation module: quantitatively analyze the internal bearing strength of the protective coal pillar and calculate the average value of the internal bearing strength of the protective coal pillar;

[0037] And, the stability assessment module: assesses the stability of the protective coal pillar based on the average external support stress on the protective coal pillar after the working face is mined and the average internal bearing strength of the protective coal pillar.

[0038] The above-mentioned method for evaluating the impact of working face mining on the stability of adjacent large faults is applied in improving the stability of large faults.

[0039] A computer storage medium stores a readable program, which can execute the above-mentioned method for evaluating the impact of working face mining on the stability of adjacent large faults when the program is running.

[0040] Beneficial effects of the present invention:

[0041] The present invention aims at the impact rock burst coal mining working face with graben (large fault) structure, and the related working face mining impact assessment and stability prevention of adjacent large faults. By establishing a model and analyzing mechanical parameters, a method for assessing the impact of working face mining on the stability of adjacent large faults is proposed, and a method for improving stability by adopting corresponding strategies based on the assessment results is provided, thereby providing methods and technologies for solving the problems of fault instability prediction and control in mining rock burst working faces. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 is a stability assessment and stability improvement flow chart of the present invention;

[0044] Figure 2 It is a schematic diagram of the spatial structure model of goaf-protective coal pillar-fault overburden of the present invention;

[0045] Figure 3 is a fault stress distribution state diagram of the present invention;

[0046] Figure 4 It is the approximate curve of the internal bearing strength of the protective coal pillar of the present invention;

[0047] Figure 5 This is a scheme diagram of the present invention for improving the stability of large faults by blasting and fracturing high-level rock formations;

[0048] Figure 6 This is a scheme diagram of improving the stability of large faults by grouting the separation layer in the goaf area of ​​the present invention;

[0049] Figure 7 It is the lateral support stress distribution diagram of the goaf area of ​​the present invention;

[0050] Figure 8 It is the distribution diagram of the fault concentration stress of the present invention;

[0051] Fig. 9 It is the distribution diagram of the external support stress of the protective coal pillar of the present invention;

[0052] Fig.10 It is the internal bearing strength distribution diagram of the protective coal pillar of the present invention;

[0053] Fig.11 This is a stability analysis diagram of the protective coal pillar of the present invention. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] Example 1

[0056] After the working face is mined to a certain extent, the rock layers above the coal seam collapse and gradually form goafs, and then form the "goaf-protective coal pillar-fault" overburden space structure. It is not difficult to find that the stress (or load) borne by the protective coal pillar at this time mainly includes: the deadweight of the overburden, the lateral transfer of the overburden structure of the adjacent goaf, and the stress concentration caused by the adjacent faults. After the working face is mined, the stress of the protective coal pillar will inevitably be redistributed and concentrated. If the width of the protective coal pillar is unreasonable, it may cause local instability of the coal pillar, and then cause a larger range of "goaf-protective coal pillar-fault" overburden space structure movement, which is very likely to cause large fault activation movement and induce rock burst. This phenomenon has been basically verified by summarizing several cases of rock burst accidents caused by fault instability caused by mining.

[0057] In order to prevent the impact of mining on the stability of adjacent large faults, the protective coal pillars left behind need to meet certain safety requirements: controlling the stability of the spatial structure of the overburden of "goaf-protective coal pillars-faults". Therefore, when evaluating before the working face is mined, stress indicators are considered to analyze whether the width of the protective coal pillars meets the above safety requirements.

[0058] like Figure 1 As shown in the figure, the method for evaluating the impact of working face mining on the stability of adjacent large faults includes the following steps:

[0059] S1, construct the spatial structure model of goaf-protective coal pillar-fault overburden, and classify the external support stress of the protective coal pillar after the working face is goafed, including: self-weight stress, lateral support stress transferred from the overburden of the goaf, and fault concentration stress formed by large faults;

[0060] like Figure 2 As shown in the goaf-protective coal pillar-fault overburden spatial structure model, the mining depth is H (unit: m), the width of the working face (goaf) is L (unit: m), the width of the protective coal pillar is D (unit: m), the overburden movement angle is α (unit: °), the low-level rock layer ("collapse zone" + "fracture zone") of the working face is h (unit: m) from the coal seam, and the high-level rock layer ("bend sinking zone") is Hh (unit: m) from the coal seam. The average thickness, average length, and average height from the coal seam of any group of key layers in the high-level rock layer are M respectively. i , L i , H i (Unit: m);

[0061] The empirical formula in the "Regulations on Coal Pillar Retention and Coal Mining in Buildings, Water Bodies, Railways and Main Wells and Lanes" is used to classify and predict the sum of the heights of the "collapse zone" and the "fracture zone": the overburden belongs to the "hard" rock layer The overburden is a "medium hard" rock layer The overburden is a "weak" rock layer Where M is the thickness of the coal seam.

[0062] from Figure 2 It can be found that the external supporting stresses on the protective coal pillar after the working face is mined include: self-weight stress, lateral supporting stress caused by the transfer of overburden in the goaf, and fault concentration stress formed by large faults.

[0063] S2, quantitatively analyze the lateral support stress and fault concentration stress in the goaf area, and calculate the average external support stress of the protective coal pillar after the working face is goafed;

[0064] S21, quantitative analysis of lateral support stress in goaf;

[0065] The lateral support pressure (lateral support stress in the goaf) σ′ (unit: MPa) generated on one side of the goaf of the working face is composed of the self-weight stress σ q (unit: MPa) and stress increment Δσ (unit: MPa), namely

[0066] σ′=Δσ+σ q (1)

[0067] In the formula, the stress increment Δσ is equal to the sum of the pressures transmitted from the exposed parts of the key layers above the goaf to the coal body on one side, that is, Δσ=Σσ i ; σ i It is the pressure transmitted to the coal body on one side by the exposed part of the i-th key layer, i=1~n.

[0068] The weight of the exposed part of each key layer transferred to the coal body on the goaf side is half of its weight, and the stress increment transferred to the coal body on the goaf side is distributed in an isosceles trapezoidal shape. Then the stress increment transferred from the i-th key layer to the coal body on the goaf side is:

[0069]

[0070] Where: maxi is the maximum bearing pressure of the i-th key layer on the coal body on one side of the goaf, σ maxi =Q i / H i cotα; α is the overburden movement angle, M i is the thickness of the i-th key layer; H i is the distance from the thickness center of the i-th key layer to the bottom of the coal seam, H i =h+M i / 2+ΣM j (j=1~i-1); L is the width of the goaf; Q i is half of the weight of the exposed part of the i-th key layer in the goaf, Q i =L i M i γ / 2; Li is the overhang length of the center position of the thickness of the i-th key layer in the goaf, L i =L+2H i cotα;γ is the bulk density of the rock formation.

[0071] The stress increment Δσ generated by the exposed part of n key layers i Superposition results in the stress increment Δσ.

[0072] Stress due to deadweight q for:

[0073]

[0074] Among them, H is the mining depth, and h is the height of the lower rock layer of the working face from the coal seam.

[0075] S22, quantitative analysis of fault concentrated stress;

[0076] According to basic experience such as the stress concentration distribution characteristics near general faults, fault drop is the main factor affecting the stress redistribution of the working face. Its corresponding stress concentration coefficient and influence range are as follows: Figure 3 As shown in Table 1, the distribution is roughly symmetrical with the fault plane as the boundary. The actual parameter selection needs to consider the fault structure distribution and the hardness of the coal and rock mass, as shown in Table 1.

[0077] Table 1 Relationship between fault drop, stress concentration factor and impact range

[0078]

[0079] In order to quantitatively analyze the stress distribution on both sides of the fault, the stress distribution on both sides of the fault is approximated as an isosceles triangle distribution. The fault stress concentration coefficient is expressed by k (dimensionless). Then the stress near both sides of the fault (fault concentration stress) σ″ (unit: MPa) can be expressed by the following piecewise function:

[0080]

[0081] Among them, a is the unilateral influence range of fault concentrated stress, and k is the fault stress concentration coefficient.

[0082] S23, combined with formulas (1) to (4), can quantitatively determine the external support stress σ (unit: MPa) of the protective coal pillar after the working face is mined:

[0083] σ=σ′+σ″ (5)

[0084] The average external support stress of the protective coal pillar after the working face is mined (Unit: MPa):

[0085]

[0086] Where D is the width of the protective coal pillar, They are the average values ​​of lateral support stress in goaf and fault concentration stress respectively.

[0087] S3, quantitatively analyzing the internal bearing strength of the protective coal pillar and calculating the average value of the internal bearing strength of the protective coal pillar;

[0088] like Figure 4 As shown in the figure, according to the methods and conclusions of relevant research, it is approximately believed that the coal body in the original rock stress zone in the middle of the protective coal pillar is in a three-dimensional stress state, and its ultimate bearing strength σ 3C (Unit: MPa) is approximately the uniaxial compressive strength of coal [σ] (Unit: MPa) times (dimensionless), the average value of the impact prone coal seam is 4, that is, σ 3C ≈4[σ]; the fracture at the edge of the coal pillar and the coal body in the plastic zone are in a progressive transition state of "unconstrained-unidirectional-two-dimensional-three-dimensional", and its ultimate bearing strength increases linearly from 0 to σ 3C , the “elastic-plastic” boundary is taken as σ 2C =2[σ], the width of the plastic zone on one side of the coal pillar is ρ (unit: m), the width of the elastic zone is t (unit: m), then the width of the original rock stress zone is D-2ρ-2t. Then the "internal bearing strength" of the protective coal pillar is σ S (Unit: MPa) The approximate expression is (the result of half width of coal pillar is calculated here, and the other half can be processed by symmetrical distribution)

[0089]

[0090] Where [σ] is the uniaxial compressive strength of the coal body, t is the width of the elastic zone of the coal pillar, and ρ is the width of the plastic zone on one side of the coal pillar. b is the coal seam mining height, δ is the coal wall side pressure coefficient, is the friction angle inside the coal body, c is the cohesion inside the coal body, f is the friction coefficient between the top and bottom plates and the coal seam contact surface, It is the internal friction angle between the contact surface between the roof and floor plates and the coal seam.

[0091] According to the above analysis, the average value of the internal bearing strength of the protective coal pillar R (unit: MPa) is approximately

[0092]

[0093] S4, based on the average external support stress of the protective coal pillar after the working face is mined out calculated by S2 and the average internal bearing strength of the protective coal pillar calculated by S3, to evaluate the stability of the protective coal pillar;

[0094] (1) Criteria for stability of protective coal pillar

[0095] If the width of the protective coal pillar is not set reasonably, the overall impact instability of the coal pillar may occur, that is, the "external support stress" acting on the coal body of the protective coal pillar exceeds the "internal bearing strength" of the coal body of the protective coal pillar, reaching the mechanical starting condition of the overall impact instability. The instability criterion is obtained by combining equations (7) to (8):

[0096]

[0097] (2) Results of stability assessment of protective coal pillars

[0098] use It represents the feasibility index of protecting the overall instability of the coal pillar, I C The larger the value, the more likely it is that an overall shock will occur. C <1.0, the overall protection coal pillar remains stable; 1.0≤I C <1.5, protect the overall weak impact of coal pillar; 1.5≤I C <2.0, moderate impact on the overall protection coal pillar; 2.0≤I C , protecting the coal pillar from strong impact as a whole.

[0099] Based on similar inventive concepts, an embodiment of the present invention also provides a computer storage medium storing a readable program, which, when running, can execute the above-mentioned method for evaluating the impact of working face mining on the stability of adjacent large faults.

[0100] Based on similar inventive concepts, an embodiment of the present invention provides an electronic device, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus;

[0101] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute operations corresponding to the above-mentioned method for evaluating the impact of working face mining on the stability of adjacent large faults.

[0102] Based on similar inventive concepts, an embodiment of the present invention also provides a computer program product, including computer instructions, which instruct a computing device to execute operations corresponding to the above-mentioned method for evaluating the impact of working face mining on the stability of adjacent large faults.

[0103] Example 2

[0104] Based on the evaluation method for the impact of working face mining on the stability of adjacent large faults proposed in Example 1, in this embodiment, an evaluation system for the impact of working face mining on the stability of adjacent large faults is proposed, including:

[0105] Spatial structure model construction module: Construct goaf-protective coal pillar-fault overburden spatial structure model, and classify the external support stress of the protective coal pillar after the working face is goafed, including: self-weight stress, lateral support stress transferred from the goaf overburden, and fault concentration stress formed by large faults;

[0106] External support stress calculation module: quantitatively analyze the lateral support stress and fault concentration stress of the goaf area, and calculate the average external support stress of the protective coal pillar after the working face is goafed;

[0107] Internal bearing strength calculation module: quantitatively analyze the internal bearing strength of the protective coal pillar and calculate the average value of the internal bearing strength of the protective coal pillar;

[0108] And, the stability assessment module: assesses the stability of the protective coal pillar based on the average external support stress on the protective coal pillar after the working face is mined and the average internal bearing strength of the protective coal pillar.

[0109] Example 3

[0110] In this embodiment, based on the evaluation results of the evaluation method for the impact of working face mining on the stability of adjacent large faults proposed in Example 1, a method for improving the stability of large faults is disclosed, such as Figure 1 As shown, including the following:

[0111] 1. Prevention methods for different types of instability

[0112] According to the above model and method, the impact of working face mining on the stability of adjacent large faults can be quantitatively evaluated before the working face is mined, and the stability of the protective coal pillar, that is, the possibility of fault activation movement, can be determined. If it is judged that the protective coal pillar may be unstable (fault activation movement), certain preventive measures need to be taken. According to the evaluation results:

[0113] (1) The overall stability of the protective coal pillar is maintained, and normal mining can be carried out without taking additional measures.

[0114] (2) To protect the overall weak impact of the coal pillar, measures should be taken to control the "local range" roof movement and the spatial structure distribution of the overburden before mining. Commonly used roof breaking techniques include blasting and hydraulic fracturing.

[0115] (3) To protect the coal pillar from medium to strong impact, a “large-scale” control of roof movement and the spatial structure distribution of the overburden rock is adopted before mining. Commonly used filling and roof control technical methods include goaf filling, separation grouting filling, etc.

[0116] 2. Prevention methods for medium to strong impacts on protective coal pillars

[0117] Taking the blasting roof breaking method as an example, blasting roof breaking (usually called forced roof caving) is a common method to control the "local range" roof movement and the spatial structure distribution of the overburden rock. Figure 5 As shown in the figure, the effects of not breaking the roof before mining and breaking the roof before mining on the roof of the goaf are compared. First, the rock layer that needs to be broken is determined through the evaluation model, and then the high-position rock layer is broken by blasting before mining before the working face is mined. This can weaken the physical and mechanical properties of the roof rock layer, promote the movement of "hanging roof" to "collapse", reduce the exposed range of the spatial structure of the overburden in the goaf, reduce the transfer of overburden load, help reduce the "external support stress" of the protective coal pillar, and improve the stability of the protective coal pillar (avoid fault activation movement); Figure 5 (a) and (b) in the figure respectively represent the method of not cutting the top before mining and the method of cutting the top before mining.

[0118] 3. Methods for preventing weak impact of the overall protection coal pillar

[0119] Taking the separation layer grouting method as an example, separation layer grouting is a common method to control the "large-scale" roof movement and the spatial structure distribution of the overburden rock, such as Figure 6 As shown in the figure, the effects of grouting before mining on the goaf roof are compared when no grouting is used and when grouting is used before mining. First, the overall instability feasibility index of the coal pillar is determined by the evaluation model, and whether it is a medium impact or a strong impact. Then, the filling rate of the goaf grouting is determined before the working face is mined (the ratio of the filling volume V to the goaf volume U is defined as the filling rate, and the larger the instability feasibility index, the larger the filling rate). The filling rate for medium impact is 50-70%, and the filling rate for strong impact is 70-100%. Appropriate grouting can form a "downward pressure + upward support" effect on the overburden in the goaf, change the overburden load transfer effect, promote the "hanging top" load to transfer to the goaf and touch the gangue downward for compaction, eliminate the overhanging state of the spatial structure of the overburden in the goaf, "release" the external support stress of the protective coal pillar on a large scale, and ensure the stability of the protective coal pillar (avoid fault activation movement). Figure 6 (a) and (b) in the figure respectively represent the schemes of not adopting separation grouting before mining and adopting separation grouting before mining.

[0120] Example 4

[0121] The following is an example of an actual coal mining project in a certain place to specifically explain the technical solution of the present invention;

[0122] 1. Basic conditions of the project

[0123] The background of this project is the 836 working face, which is located in the northeast part of the mining area. The mining depth H of the 836 mining working face area is 376-477m, with an average of about H=426.5m. The width of the goaf is 61-114m, with an average of about L=87.5m. The 3 coal seams are nearly horizontally distributed with an average coal seam thickness of M=6.0m, a protective coal pillar width of D=115m, and an average bulk density of the overburden γ=25KN / m 3The overburden movement angle α is 80°. The SDF17 large fault adjacent to the protective coal pillar is a normal fault with a drop of 10 to 100 m. The uniaxial compressive strength of the coal body of the protective coal pillar is [σ] = 12.464 MPa, and the coal seam has an impact tendency.

[0124] 2. Quantitative analysis of “external support stress” on coal protection pillars

[0125] (1) Quantitative analysis of lateral support stress σ′ in goaf

[0126] The lateral support pressure σ′ (unit: MPa) generated on one side of the goaf of the working face is composed of the deadweight stress σ q (unit: MPa) and stress increment Δσ (unit: MPa), namely

[0127] σ′=Δσ+σ q

[0128] Since the overlying rock layer on the roof of coal 3 is hard sandstone, the sum of the heights of the "collapse zone" and "fracture zone" h is calculated according to the empirical formula in the "Regulations on Coal Pillar Retention and Coal Mining for Buildings, Water Bodies, Railways and Main Wells and Lanes", and the height of the low rock layer of the working face is The average is about 65.2m, and the height of the high rock layer at the working face Hh is 361.3m. Combined with formula (2) and relevant data, the lateral support stress σ′ of the goaf is quantitatively analyzed (when conducting the quantitative analysis of the lateral support stress of the goaf, the key layer overlying the goaf is calculated as a whole hard rock layer), x is the distance from the coal body protecting the coal pillar to the side boundary of the goaf.

[0129]

[0130] Combining formula (3) and substituting relevant data into the stress σ generated by self-weight q Conduct quantitative analysis

[0131]

[0132] Combining equations (10) to (11) and substituting relevant data, we can obtain the piecewise function of the lateral support pressure σ′ generated on one side of the goaf area of ​​the working face and the lateral support stress distribution diagram of the goaf area (such as Figure 7 As shown in the figure, it can be found that due to the influence of overburden load transfer, the lateral support pressure of the coal body protecting the coal pillar has obvious pressure reduction zone (0-30m away from the boundary of the goaf), pressure increase zone (30-86.7m away from the boundary of the goaf), and original rock stress zone (86.7-115m away from the boundary of the goaf). The maximum impact distance of overburden load transfer in the goaf is about 86.7m.

[0133]

[0134] 2. Quantitative analysis of fault concentrated stress σ″

[0135] According to the actual engineering conditions, the stress concentration coefficient k = 1.4, the unilateral influence range a = 30m, combined with formula (4) and the relevant data, the fault concentration stress is quantitatively analyzed to obtain the piecewise function of the fault concentration stress σ″ and the fault concentration stress distribution diagram (such as Figure 8 shown).

[0136]

[0137] 3. Protect the "external support stress" of the coal pillar

[0138] Combining equations (12) to (13) and equation (5) and bringing in relevant data, a quantitative analysis is performed on the “external support stress σ” of the protective coal pillar after the working face is mined (σ′ and σ″ are stress superimposed, i.e., σ=σ′+σ″), and the piecewise function of the “external support stress σ” and the distribution diagram of the “external support stress σ” are obtained (e.g. Fig. 9 shown).

[0139]

[0140] Combined with formula (6), the average "external support stress" of the protective coal pillar after the working face is mined is obtained:

[0141]

[0142] 4. Quantitative analysis of the “internal bearing strength” of the protective coal pillar

[0143] For the quantitative calculation of the "internal bearing strength" of the protective coal pillar, the coal seam mining height b = 6m, the coal wall side pressure coefficient δ = 0.6, and the internal friction angle of the coal body Coal body cohesion c = 0.87MPa, internal friction angle of the contact surface between the roof and the bottom plate and the coal seam Friction factor of the contact surface between roof and floor and coal seam The width of the plastic zone is 5.73m, the width of the elastic zone is 6.25m, and the width of the original rock stress zone is 91.04m. Combining formula (7) and substituting relevant data, the internal bearing strength σ of the protective coal pillar is obtained. s "The piecewise function and the internal bearing strength σ of the protective coal pillar s "Distribution map (such as Fig.10 shown);

[0144]

[0145] Combining formula (8) we can get the average value R of the “internal bearing strength” of the protective coal pillar.

[0146]

[0147] 5. Analysis of stability of protective coal pillar

[0148] (1) Comparison between “external support stress” and “internal bearing strength” of protective coal pillar

[0149] According to the previous article Fig. 9 , Fig.10 The “external support stress” of the protective coal pillar and the “internal bearing strength” of the protective coal pillar are used to analyze the stability of the protective coal pillar. Fig.11 As shown in the figure:

[0150] 1) The “external support stress” of the protective coal pillar is distributed in the following order: rise → fall → rise → fall:

[0151] From 0 to 11.49 m, the "external support stress" of the protective coal pillar starts from 12.3 MPa and gradually increases, reaching a peak of 25.84 MPa at 43.35 m.

[0152] From 11.49m to 85m, the "external support stress" of the protective coal pillar starts from 25.84MPa and gradually shows a downward trend, reaching 21.70MPa at 85m;

[0153] From 85m to 100m, the "external support stress" of the protective coal pillar starts from 21.70MPa and shows an upward trend, reaching 25.54MPa at 100m;

[0154] From 100m to 115m, the external support stress starts from 25.54MPa and shows a downward trend, reaching 21.14MPa at 115m.

[0155] 2) The "internal bearing strength" of the protective coal pillar is approximately in a trapezoidal distribution state of rising → horizontal → descending:

[0156] From 0 to 11.98 m, the “internal bearing strength” of the protective coal pillar starts from 0 MPa and gradually shows an upward trend, reaching a peak of 49.856 MPa at 11.98 m;

[0157] From 11.98m to 108.75m, the “internal bearing strength” of the protective coal pillar remained at a peak value of 49.856MPa, showing a horizontal state;

[0158] From 108.75m to 115m, the “internal bearing strength” of the protective coal pillar starts from 49.856MPa and shows a downward trend, reaching the lowest value of 0MPa at 115m.

[0159] 3) At 0-2.97m and 109.76-115m from the side boundary of the goaf, the "internal bearing strength" of the protective coal pillar is lower than the "external supporting stress" it is subjected to. The protective coal pillar is prone to "local" instability due to impact, and the impact is relatively small. Monitoring (microseismic monitoring, etc.) can be strengthened during the mining process.

[0160] (2) Results of stability assessment of protective coal pillars

[0161] Substituting the relevant data into equation (9), we get the instability criterion: Protect the overall stability of the coal pillar, the same as below Fig.11 As shown, the "internal bearing strength" of the protective coal pillar in most areas is much higher than the "external supporting stress" of the protective coal pillar. The protective coal pillar remains stable as a whole and can be mined normally without taking additional measures (i.e., there is no need to use roof breaking or filling techniques).

[0162] At present, the 836 working face has been mined safely. During the mining process, the protective coal pillar and the SDF17 large fault remained relatively stable, and no large fault instability was observed, which was consistent with the pre-mining assessment results, verifying the rationality and reliability of the proposed method and model.

[0163] The method of the present invention may be implemented in hardware, firmware, or as software or computer code that may be stored in a recording medium (such as a CDROM, RAM, floppy disk, hard disk, or magneto-optical disk), or as computer code that is originally stored in a remote recording medium or a non-temporary machine-readable medium downloaded over a network and will be stored in a local recording medium, so that the method described herein may be stored in such software processing on a recording medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware (such as an ASIC or FPGA). It is understood that a computer, processor, microprocessor controller, or programmable hardware includes a storage component (e.g., RAM, ROM, flash memory, etc.) that can store or receive software or computer code, and when the software or computer code is accessed and executed by a computer, processor, or hardware, the method described herein is implemented. In addition, when a general-purpose computer accesses the code for implementing the method shown herein, the execution of the code converts the general-purpose computer into a dedicated computer for executing the method shown herein.

[0164] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for evaluating the impact of working face mining on the stability of adjacent large faults, characterized in that: The following steps are involved: A spatial structural model of goaf-protective coal pillar-fault overburden was constructed to classify the external support stress on the protective coal pillar after the working face was mined, including self-weight stress, lateral support stress transferred from the goaf overburden, and fault concentration stress formed by large faults. Quantitatively analyze the lateral support stress and fault concentration stress in the goaf area, and calculate the average external support stress of the protective coal pillar after the working face is goafed; Conduct quantitative analysis on the internal bearing strength of the protective coal pillar and calculate the average value of the internal bearing strength of the protective coal pillar; The stability of the protective coal pillar is evaluated based on the average external support stress of the protective coal pillar after the working face is mined and the average internal bearing strength of the protective coal pillar.

2. The method for evaluating the impact of working face mining on the stability of adjacent large faults according to claim 1 is characterized in that: The steps for calculating the average external support stress of the protective coal pillar after the working face is mined include: S21, quantitative analysis of lateral support stress in goaf; S22, quantitative analysis of fault concentrated stress; S23, determine the external support stress on the protective coal pillar after the working face is mined out, and calculate the average external support stress on the protective coal pillar after the working face is mined out.

3. The method for evaluating the impact of working face mining on the stability of adjacent large faults according to claim 2 is characterized in that: The calculation formula of the lateral support stress σ′ in the goaf is: σ′=Δσ+σ q Where Δσ is the stress increment, Δσ=Σσ i ; σ i is the pressure transmitted from the exposed part of the i-th key layer to the coal body on one side, i = 1~n; σ q is the self-weight stress; σ maxi is the maximum bearing pressure of the i-th key layer on the coal body on one side of the goaf, σ maxi =Q i / H i cotα; α is the overburden movement angle, M i is the thickness of the i-th key layer; H i is the distance from the thickness center of the i-th key layer to the bottom of the coal seam, H i =h+M i / 2+ΣM j (j=1~i-1); L is the width of the goaf; Q i is half of the weight of the exposed part of the i-th key layer in the goaf, Q i =L i M i γ / 2; L i is the overhang length of the center position of the thickness of the i-th key layer in the goaf, L i =L+2H i cotα; γ is the bulk density of the rock layer; the stress increment Δσ generated by the exposed part of n key layers i Superposition is performed to obtain the stress increment Δσ; H is the mining depth, and h is the height of the lower rock layer of the working face from the coal seam.

4. The method for evaluating the impact of working face mining on the stability of adjacent large faults according to claim 3 is characterized in that: The calculation formula of fault concentration stress σ″ is: Among them, a is the unilateral influence range of fault concentrated stress, and k is the fault stress concentration coefficient.

5. The method for evaluating the impact of working face mining on the stability of adjacent large faults according to claim 4, characterized in that: The external support stress σ of the protective coal pillar after the working face is mined is: σ=σ′+σ″ Average external support stress of the protective coal pillar after the working face is mined for: Where D is the width of the protective coal pillar, They are the average values ​​of lateral support stress in goaf and fault concentration stress respectively.

6. The method for evaluating the impact of working face mining on the stability of adjacent large faults according to claim 4, characterized in that: The calculation formula for the average value R of the internal bearing strength of the protective coal pillar is: Where [σ] is the uniaxial compressive strength of the coal body, t is the width of the elastic zone of the coal pillar, and ρ is the width of the plastic zone on one side of the coal pillar. b is the coal seam mining height, δ is the coal wall side pressure coefficient, is the friction angle inside the coal body, c is the cohesion inside the coal body, f is the friction coefficient between the top and bottom plates and the coal seam contact surface, It is the internal friction angle between the contact surface between the roof and floor plates and the coal seam.

7. The method for evaluating the impact of working face mining on the stability of adjacent large faults according to claim 1, characterized in that: When evaluating the stability of the protective coal pillar, I C To quantitatively characterize the feasibility index of protecting the overall instability of the coal pillar: in, is the average external support stress of the protective coal pillar after the working face is mined, and R is the average internal bearing strength of the protective coal pillar; I C The larger the value, the more feasible it is to protect the coal pillar from overall impact. C <1.0, the overall protection coal pillar remains stable; 1.0≤I C <1.5, protect the overall weak impact of coal pillar; 1.5≤I C <2.0, protect the overall moderate impact of the coal pillar; 2.0≤I C , protecting the coal pillar from strong impact as a whole.

8. An evaluation system for the impact of working face mining on the stability of adjacent large faults, characterized in that: include: Spatial structure model construction module: Construct goaf-protective coal pillar-fault overburden spatial structure model, and classify the external support stress of the protective coal pillar after the working face is goafed, including: self-weight stress, lateral support stress transferred from the goaf overburden, and fault concentration stress formed by large faults; External support stress calculation module: quantitatively analyze the lateral support stress and fault concentration stress of the goaf area, and calculate the average external support stress of the protective coal pillar after the working face is goafed; Internal bearing strength calculation module: quantitatively analyze the internal bearing strength of the protective coal pillar and calculate the average value of the internal bearing strength of the protective coal pillar; And, the stability assessment module: assesses the stability of the protective coal pillar based on the average external support stress on the protective coal pillar after the working face is mined and the average internal bearing strength of the protective coal pillar.

9. Application of the method for evaluating the impact of working face mining on the stability of adjacent large faults as described in any one of claims 1 to 7 in improving the stability of large faults.

10. A computer storage medium storing a readable program, characterized in that: When the program is running, it can execute the method for evaluating the impact of working face mining on the stability of adjacent large faults as described in any one of claims 1-7.

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