Method for determining stability of caving roof during layered stoping under large-dip-angle layered mining working face

Abstract

The invention relates to the technical field of coal mining, in particular to a method for determining the stability of a caving roof during layered stoping under a large-dip-angle layered mining working face. According to the method, the coal seam stability of the working face is analyzed through calculation of the minimum staggered distance of the goaf and the working face, the shortest time of goaf compaction and fuzzy clustering analysis, and the method for determining the stability of the caving roof during layered stoping under the large-dip-angle layered mining working face is provided. Comprising the following steps: S100: carrying out basic parameter test and statistics on coal and rock masses and interfaces at a stope face and a top plate and a bottom plate of the stope face, and peeping top plates of a transportation crossheading and an air return crossheading; s200, respectively calculating the minimum staggered distance of the goaf and the working face according to the supporting pressure superposition and the stability of the goaf; s300, the shortest compaction time of the goaf is calculated; and S400, mining the stability of the regional coal seam through the fuzzy clustering index.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining, in particular to a method for determining the stability of a collapsed roof during layered mining under a large-angle layered mining working face. Background Art

[0002] The field of coal mining technology is a hot topic in coal mining research. In order to ensure the safety of coal mining, it is first necessary to determine the stability of the collapsed roof during layered mining under the high-angle layered mining face to ensure the stability of the collapsed roof, reduce accidents, and ensure personnel safety.

[0003] Aiming at the above problems, this method is a method for determining the stability of collapsed roof during stratified mining under a large-angle stratified mining face. The stability of collapsed roof during stratified mining under a large-angle stratified mining face is mainly analyzed by fuzzy clustering. Specifically, the working face profile and the mechanical properties of coal and its roof and floor rocks need to be determined first, and the roofs of the transport chute and the return air chute are observed to determine the stability of the large-angle stratified working face before mining; the minimum offset between the goaf and the working face is calculated according to the superposition of supporting pressure and the stability of the goaf; the shortest compaction time of the goaf is calculated; finally, the fuzzy clustering index is selected to analyze the stability of the collapsed roof. Summary of the invention

[0004] The present invention analyzes the stability of the coal seam on the working face by calculating the minimum offset between the goaf and the working face, the shortest time for goaf compaction and fuzzy clustering analysis, and provides a method for determining the stability of the collapsed roof during layered mining under a large-angle layered mining working face.

[0005] The present invention adopts the following technical scheme: a method for determining the stability of collapsed roof during stratified mining under a large-angle stratified mining working face, comprising: S100: Conduct basic parameter testing and statistics on the coal-rock mass and interface at the mining face and its roof and floor, and observe the roof of the transport chute and return air chute; S200: Calculate the minimum offset between the goaf and the working face according to the superposition of support pressure and the stability of the goaf; S300: Calculating the shortest compaction time of the goaf; S400: Stability of coal seams in mining areas through fuzzy clustering indicators.

[0006] In some embodiments, in step S100, the basic parameters of the coal and rock mass of the mining face and its roof and floor include the uniaxial compressive strength and softening coefficient of coal and rock, elastic modulus, Poisson's ratio, tensile strength, shear strength, cohesion and internal friction angle; the roof of the transport chute and the return air chute is inspected to judge the overall stability of the roof and determine the ideal support layer position.

[0007] In some embodiments, in step S200, The stability of the collapsed roof of the upper layer goaf is related to the strike offset between the goaf and the working face. The advanced support pressure of the lower layer working face and the interlayer stress superposition affect the stability of the collapsed roof of the upper layer goaf. The mining of the lower layer working face should lag behind the upper layer working face by a certain distance to maintain a reasonable strike offset. The influence range of upper layer mining on the stress of lower layer can be calculated according to the following equation: Where K is the stress concentration coefficient; γ is the average bulk density of the overlying rock layer; H is the buried depth of the coal seam; f is the friction factor between the layers; M is the mining height of the upper layer working face; C is the cohesion of the coal body in the upper coal seam; φ is the internal friction angle of the coal body in the upper layer; The influence range of lower coal seam support pressure: Where: γ is the average bulk density of the overburden; H is the buried depth of the coal seam; K is the stress concentration coefficient; M is the mining height of the lower layer working face; C is the cohesion of the coal body in the lower coal seam; φ is the internal friction angle of the coal body in the lower coal seam; f is the friction factor between the layers; λ is the proportional coefficient; Considering the stability of the roof of the upper layer goaf and the movement of the rock layer, the strike offset should be determined according to the stability of the roof of the upper layer goaf: La is the periodic pressure step distance of the upper layer working face; n is the safety factor; Lz is the influence range of the lower layer mining trend.

[0008] In some embodiments, in step S300, the empirical formula for calculating the stabilization time of the goaf of the fully mechanized caving long-arm working face is as follows: T=7+H / c Where c is the advancing speed, m / d; H is the coal seam burial depth, m. Thus, the shortest compaction time of the goaf can be calculated.

[0009] In some embodiments, in step S400, Fuzzy cluster analysis is used to analyze the indicators and calculate the fuzzy relationship matrix R. The fuzzy relationship matrix R is established by the correlation coefficient and is a quantitative indicator used to measure the closeness of the relationship between two variables. ij The calculation formula is as follows: Where, is the average value of each index value of the i-th sample after standardization; is the average value of each index value of the j-th sample after standardization; Clustering is to establish a fuzzy equivalence relationship matrix based on the fuzzy similarity relationship matrix R. Given different λ∈[0,1], horizontal interception is performed to obtain different classifications. The smaller λ is, the fewer and coarser the classifications are. The larger λ is, the more and finer the classifications are. When it is small to a certain extent, all samples are divided into one category. When λ=1, each sample lane is a category in itself. When predicting the coal rock stability category, the comment set is V = (category I, II, III, IV, V), with a total of 5 categories; the factor set is U = (roof strength, coal seam strength, floor strength, mining influence coefficient, tunnel burial depth, residual mining influence coefficient, rock mass integrity index, i.e., the first collapse step of the direct roof), with a total of 7 factors. The results of fuzzy comprehensive evaluation are: B=AR Where B is the fuzzy comment set of lane categories; A is the weight set of each classification index; and R is the available evaluation matrix of fuzzy relations. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The support pressure distribution of the working face of the coal seam for stratified mining; Figure 2 The small strike offset leads to the increase of coal support pressure in the lower layer working face; Figure 3 To maintain a reasonable strike offset and avoid a significant increase in the support pressure of the lower layered working face; Figure 4 Calculate the model for the influence range of the floor for upper layer mining; Figure 5 It is a calculation model for the influence range of support pressure in lower layer mining. DETAILED DESCRIPTION

[0011] The present invention provides a method for determining the stability of collapsed roof during stratified mining under a high-angle stratified mining working face. The principle of the method is to determine the stability of collapsed roof by determining fuzzy clustering indexes and performing fuzzy clustering analysis.

[0012] The above-mentioned purpose of the present invention is achieved through the following technical solutions.

[0013] S100: Test and count the basic parameters of the coal-rock mass and interface at the mining face and its roof and floor; the basic parameters of the coal-rock mass at the mining face and its roof and floor include the uniaxial compressive strength and softening coefficient of coal and rock, elastic modulus, Poisson's ratio, tensile strength, shear strength, cohesion and internal friction angle; observe the roof of the transport chute and the return air chute.

[0014] The specific process is to process the samples after sampling underground. Use an electro-hydraulic servo universal testing machine to measure the uniaxial compressive strength and softening coefficient of the samples, the elastic modulus and Poisson's ratio of the rock samples, and the tensile strength. The electro-hydraulic servo universal testing machine and the 45°, 55°, and 65° variable angle meters are used to measure the shear strength of coal and rock specimens; when peeping, insert the probe of the mining borehole imaging instrument into the borehole, observe the borehole shape on the display screen, and then push the peeping camera forward slowly to record the corresponding surrounding rock depth, and at the same time record the corresponding time and video files, so as to capture the rock formation conditions at different hole depths.

[0015] S200: Calculate the minimum offset between the goaf and the working face according to the superposition of support pressure and the stability of the goaf; The stability of the collapsed roof of the upper layer goaf is related to the strike offset between the goaf and the working face. The advanced support pressure of the lower layer working face and the interlayer stress superposition affect the stability of the collapsed roof of the upper layer goaf. The mining of the lower layer working face should lag behind the upper layer working face by a certain distance to maintain a reasonable strike offset.

[0016] The influence range of upper layer mining on the stress of lower layer can be calculated according to the following equation: Where K is the stress concentration coefficient; γ is the average bulk density of the overlying rock strata; H is the buried depth of the coal seam; f is the friction factor between the layers; M is the mining height of the upper layer working face; C is the cohesion of the coal body in the upper coal seam; φ is the internal friction angle of the coal body in the upper layer.

[0017] Considering the stability of the roof of the upper layer goaf and the movement of the rock layer, the strike offset should be determined according to the stability of the roof of the upper layer goaf: La is the periodic pressure step distance of the upper layer working face; n is the safety factor; Lz is the influence range of the lower layer mining trend.

[0018] S300: Calculating the shortest compaction time of the goaf; The empirical formula for calculating the stabilization time of the goaf in the fully mechanized caving long-arm working face is as follows: T=7+H / c Where c is the advancing speed, m / d; H is the coal seam burial depth, m. Thus, the shortest compaction time of the goaf can be calculated.

[0019] S400: Analyzing the stability of coal seams in mining areas through fuzzy clustering indicators.

[0020] Select fuzzy clustering index and its measurement method, For the selection of three surrounding rock strength indicators, the surrounding rock strength of the tunnel is calculated according to the actual measured strength. The unidirectional compressive strength of the roof and floor rocks is the weighted average of the unidirectional compressive strength of the roof and floor rock layers within 2 times and 1 times the tunnel width, respectively. For the selection of tunnel burial depth H, the tunnel burial depth refers to the vertical distance between the location of the tunnel and the ground surface. For inclined tunnels, the average value can be taken in sections. For the selection of the initial collapse step distance L of the direct roof, the surrounding rock integrity index refers to the degree of influence of the surrounding rock joints, cracks, and bedding. For the mining impact index of the mining tunnel, the mining impact is divided into the residual mining impact of the current section and the adjacent section. The mining impact index N is selected to be equal to the thickness of the direct roof divided by the mining height of the coal seam. For the width of the coal pillar protecting the tunnel (X), the actual coal pillar width on one side of the tunnel is selected.

[0021] To perform fuzzy cluster analysis, first calculate the cluster analysis matrix R, the calculation formula is as follows: In the formula, is the average value of each index value of the i-th sample after standardized processing; is the average value of each indicator value of the jth sample after standardized processing.

[0022] On the basis of the fuzzy similarity relation matrix R, a fuzzy equivalent relation matrix is ​​established. Given different λ∈[0,1], horizontal interception is performed to obtain different classifications. The smaller λ is, the fewer and coarser the classifications are; the larger λ is, the more and finer the classifications are.

[0023] The final result of fuzzy comprehensive evaluation is: B=AR Where B is the fuzzy comment set of lane categories; A is the weight set of each classification index; and R is the available evaluation matrix of fuzzy relations.

Claims

1. A method for determining the stability of collapsed roof during stratified mining under a high-angle stratified mining working face, characterized in that: include: S100: Conduct basic parameter testing and statistics on the coal-rock mass and interface at the mining face and its roof and floor, and observe the roof of the transport chute and return air chute; S200: Calculate the minimum offset between the goaf and the working face according to the superposition of support pressure and the stability of the goaf; S300: Calculating the shortest compaction time of the goaf; S400: Stability of coal seams in mining areas through fuzzy clustering indicators.

2. The method for determining the stability of collapsed roof during stratified mining under a high-angle stratified mining working face according to claim 1 is characterized in that: In step S100, the basic parameters of the coal and rock mass of the mining face and its roof and floor include the uniaxial compressive strength and softening coefficient of coal and rock, elastic modulus, Poisson's ratio, tensile strength, shear strength, cohesion and internal friction angle; the roof of the transport chute and the return air chute is inspected to judge the overall stability of the roof and determine the ideal support layer position.

3. The method for determining the stability of collapsed roof during stratified mining under a high-angle stratified mining working face according to claim 1 is characterized in that: In step S200, The stability of the collapsed roof of the upper layer goaf is related to the strike offset between the goaf and the working face. The advanced support pressure of the lower layer working face and the interlayer stress superposition affect the stability of the collapsed roof of the upper layer goaf. The mining of the lower layer working face should lag behind the upper layer working face by a certain distance to maintain a reasonable strike offset. The influence range of upper layer mining on the stress of lower layer can be calculated according to the following equation: Where K is the stress concentration coefficient; γ is the average bulk density of the overlying rock layer; H is the buried depth of the coal seam; f is the friction factor between the layers; M is the mining height of the upper layer working face; C is the cohesion of the coal body in the upper coal seam; φ is the internal friction angle of the coal body in the upper layer; The influence range of lower coal seam support pressure: Where: γ is the average bulk density of the overburden; H is the buried depth of the coal seam; K is the stress concentration coefficient; M is the mining height of the lower layer working face; C is the cohesion of the coal body in the lower coal seam; φ is the internal friction angle of the coal body in the lower coal seam; f is the friction factor between the layers; λ is the proportional coefficient; Considering the stability of the roof of the upper layer goaf and the movement of the rock layer, the strike offset should be determined according to the stability of the roof of the upper layer goaf: La is the periodic pressure step distance of the upper layer working face; n is the safety factor; Lz is the influence range of the lower layer mining trend.

4. The method for determining the stability of collapsed roof during stratified mining under a high-angle stratified mining working face according to claim 1 is characterized in that: In step S300, the empirical formula for calculating the stabilization time of the goaf of the fully mechanized caving long-arm working face is as follows: T=7+H / c Where c is the advancing speed, m / d; H is the coal seam burial depth, m. Thus, the shortest compaction time of the goaf can be calculated.

5. The method for determining the stability of collapsed roof during stratified mining under a high-angle stratified mining working face according to claim 1, characterized in that: In step S400, Fuzzy cluster analysis is used to analyze the indicators and calculate the fuzzy relationship matrix R. The fuzzy relationship matrix R is established by the correlation coefficient and is a quantitative indicator used to measure the closeness of the relationship between two variables. ij The calculation formula is as follows: In the formula, is the average value of each index value of the i-th sample after standardized processing; is the average value of each index value of the jth sample after standardized processing; Clustering is to establish a fuzzy equivalence relationship matrix based on the fuzzy similarity relationship matrix R. Given different λ∈[0,1], horizontal interception is performed to obtain different classifications. The smaller λ is, the fewer and coarser the classifications are. The larger λ is, the more and finer the classifications are. When it is small to a certain extent, all samples are divided into one category. When λ=1, each sample lane is a category in itself. When predicting the coal rock stability category, the comment set is V = (category I, II, III, IV, V), with a total of 5 categories; the factor set is U = (roof strength, coal seam strength, floor strength, mining influence coefficient, tunnel burial depth, residual mining influence coefficient, rock mass integrity index, i.e., the first collapse step of the direct roof), with a total of 7 factors. The results of fuzzy comprehensive evaluation are: B=AR Where B is the fuzzy comment set of lane categories; A is the weight set of each classification index; and R is the available evaluation matrix of fuzzy relations.

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