A dynamic evaluation method for comprehensive stability of working face and surrounding rock support conditions

Abstract

The invention discloses a method for dynamically evaluating the comprehensive stability of a working face and surrounding rock support conditions, comprising the following steps: S1, obtaining four status indicators that affect the evaluation of the working face; S2, building a roof stability evaluation system through the four status indicators, the roof stability evaluation system including seven roof stability evaluation indicators; S3, calculating a roof stability value score through an entropy method; S4, building a working face support strength evaluation system, the working face support strength evaluation system including four support quality evaluation indicators; S5, calculating a support quality value score through an entropy method; S6, determining a comprehensive stability rating of the working face through roof stability value score analysis; and determining a surrounding rock support quality rating through support quality value score analysis.

Description

Technical Field

[0001] The invention relates to the field of coal mining, and in particular to a method for dynamically evaluating the comprehensive stability of a working face and surrounding rock support conditions. Background Art

[0002] At present, the existing coal mine working face roof stability evaluation is usually only based on the development status of the basic top rock layer exposed by the tunnel, or only the status of the sampled rock layer is evaluated, which is quite one-sided. At the same time, the existing coal mine working face stability evaluation method only considers the surrounding rock status, and does not associate the working face with the state of the near-goaf area, the real-time bearing status of the support, the periodic pressure of the working face and other factors, which leads to great limitations in its evaluation results and low evaluation accuracy. Summary of the invention

[0003] The purpose of the present invention is to provide a method for dynamically evaluating the comprehensive stability of a working face and surrounding rock support conditions with improved evaluation accuracy in order to solve the above problems.

[0004] In order to achieve the above object, the technical solution of the present invention is:

[0005] A method for dynamically evaluating the comprehensive stability of a working face and surrounding rock support conditions comprises the following steps:

[0006] S1. Obtain the roof stratum status index, adjacent goaf stress influence status index, basic roof stability status index, and direct roof stability status index that affect the working face evaluation;

[0007] S2. The roof stability evaluation system is established through the roof rock state index, the stress influence state index of the adjacent goaf, the basic roof stability state index, and the direct roof stability state index. The roof stability evaluation system includes seven roof stability evaluation indexes, which are: rock mass integrity coefficient, rock mass joint gap, rock mass layer gap, working face square state, working face pressure dynamic load coefficient, roof crushing rate, and roof crushing coefficient;

[0008] S3, calculate the roof stability value score by entropy method;

[0009] S4. Establish a working face support strength evaluation system. The working face support strength evaluation system includes four support quality evaluation indicators: roof stability value score, working face support pressure real-time compliance rate, support safety valve real-time opening rate, and support resistance surplus;

[0010] S5. Calculate the support quality value score by entropy method;

[0011] S6. Determine the comprehensive stability rating of the working face through roof stability value score analysis; determine the surrounding rock support quality rating through support quality value score analysis.

[0012] Furthermore, in step S2, rock mass integrity coefficient = (rock mass longitudinal wave velocity / rock longitudinal wave velocity in laboratory) 2 .

[0013] Furthermore, in step S2, when obtaining the rock mass joint gap, firstly, drilling is performed in the selected working surface area, and then a borehole image of the rock mass is obtained using a borehole peep instrument, and then the rock mass joint gap is obtained by observing the rock mass borehole image.

[0014] Furthermore, in step S2, when obtaining the rock layer gap, first use a borehole viewer to obtain a rock borehole image, then determine the position of each rock layer based on the color, shape, and particle size of the rock in the rock borehole image, and finally determine the rock layer gap based on the single-layer thickness of the rock layer.

[0015] Furthermore, in step S2, the square status of the working face is: if the working face is not squared, 0 is output; if the working face is squared for the first time, 1 is output; if the working face is squared for multiple times or the goaf of the working face is squared, 2 is output.

[0016] Furthermore, in step S2, the dynamic load coefficient of the working surface pressure = the average support pressure / the average pressure of all supports on the working surface in the past 10 days.

[0017] Furthermore, in step S2, the top plate crushing rate = e / J; the top plate crushing coefficient α 1 =P 1 / P 2 ; Where, e is the number of supports in the roof crushing area; J is the total number of supports on the working surface; P 1 is the average support pressure of the e-stage support; P 2 It is the average support pressure of all supports on the working surface.

[0018] Furthermore, in step S3, calculating the roof stability value score by entropy method includes the following steps:

[0019] S31. Collect m samples in the laboratory or in actual application;

[0020] S32, constructing the original data matrix of m samples and various roof stability evaluation indicators; obtaining:

[0021]

[0022] Among them, X ij represents the value of the j-th roof stability evaluation index of the i-th sample;

[0023] S33, eliminate the influence of different dimensions on the evaluation results, and standardize the various roof stability evaluation indicators; obtain:

[0024] When the larger the indicator is, the more beneficial it is to the development of the system, the positive indicator calculation formula is adopted; the calculation formula is:

[0025] Positive indicators:

[0026] When the smaller the indicator is, the more beneficial it is to the development of the system, the negative indicator calculation formula is adopted: The calculation formula is:

[0027] Negative indicators:

[0028] Among them, X′ ij is the standardized value of the jth indicator of the i-th sample; X j is the jth index value of the i-th sample; X min is the minimum value of the jth index of the i-th sample; X max is the maximum value of the jth index of the i samples;

[0029] S34, calculate the proportion of the i-th sample value under the j-th roof stability evaluation index; the calculation formula is:

[0030]

[0031] Among them, P ij is the proportion of the i-th sample value under the j-th indicator; X′ ij is the standardized value of the i-th sample; n is the total number of evaluation indicators;

[0032] S35. Calculate the entropy value, and the calculation formula is:

[0033]

[0034] in, e j is the information entropy value of the jth indicator; n is the total number of evaluation indicators; m is the number of samples; P ij is the proportion of the i-th sample value under the j-th indicator;

[0035] S36. Obtain the coefficient of difference, the calculation formula is:

[0036] g j =1-e j ;

[0037] Among them, g j is the coefficient of difference of the j-th indicator; e j is the information entropy value of the j-th indicator;

[0038] S37, obtain the weight, the calculation formula is:

[0039]

[0040] Among them, W j is the weight of the jth indicator; g j is the coefficient of variation of the jth indicator; m is the number of samples;

[0041] S38. Calculate the roof stability value score, the calculation formula is:

[0042]

[0043] Among them, S i is the roof stability value score of the i-th scheme; W j is the weight of the jth indicator of the ith solution; P ij is the proportion of the i-th sample value under the j-th indicator; m is the number of samples.

[0044] Furthermore, in step S4, the real-time compliance rate of the working face support pressure = the number of supports that meet the pressure standard / the total number of supports; the real-time opening rate of the support safety valve = the number of supports that exceed the pressure limit / the total number of supports; the surplus support resistance = the number of supports with surplus pressure / the total number of supports.

[0045] Furthermore, in step S5, calculating the support quality value score by the entropy method includes the following steps:

[0046] S51. Calculate the weight of each support quality evaluation index using the entropy method;

[0047] S52. The support quality value score is obtained by weighting each support quality evaluation index.

[0048] Compared with the prior art, the present invention has the following advantages and positive effects:

[0049] The present invention analyzes all factors, including the development state of basic roof rock joints, the impact of goaf caused by mining technology, the impact of roof pressure, the impact of real-time bearing and roof crushing degree, and the impact of roof surrounding rock stability. From different angles and aspects, the present invention dynamically evaluates the roof stability state of the working face more objectively and accurately, solves the limitations of existing working face stability assessment methods, improves the accuracy of working face stability assessment, and further guarantees the safety of coal mining work. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] 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, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0051] Figure 1 It is a framework structure diagram of the present invention. DETAILED DESCRIPTION

[0052] 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, any modifications, equivalent substitutions, improvements, etc., should be included in the protection scope of the present invention.

[0053] like Figure 1 As shown, this embodiment discloses a method for dynamically evaluating the comprehensive stability of a working face and surrounding rock support conditions. After analysis, the main factors affecting the stability of the top plate of the working face are: the state of the top plate rock mass, the stress influence state of the adjacent goaf, the basic top stability of the working face, and the direct top stability of some areas of the working face;

[0054] 1. Steps for determining the occurrence status of roof rock mass;

[0055] Calculate the state of the roof rock mass and use three indicators, integrity coefficient, joint gap, and bedding gap, to judge the state of the rock formation;

[0056] Rock mass integrity coefficient = (rock mass longitudinal wave velocity / rock longitudinal wave velocity in laboratory) 2 ;

[0057] Judgment of rock joint gaps: Drill holes in the selected working surface area, use a borehole peep to obtain rock borehole images, and then use image observation to judge the size of rock joint gaps;

[0058] Bedding gap judgment: Use a borehole peep to obtain the rock mass borehole image, judge the position of each rock layer according to the different colors, shapes, and granularity of the rock mass, and determine the size of the rock layer based on the thickness of the single layer of the rock layer;

[0059] Roof stability classification: According to the three major indexes of integrity coefficient, joint gap and bedding gap, the rock mass is divided into five categories: extremely broken rock layer, relatively broken rock layer, medium rock layer, relatively complete rock layer and complete rock layer (as shown in the following table).

[0060] Extremely broken rock Broken rock Medium rock More complete rock formation Complete rock formation Integrity factor <0.55 0.55-0.65 0.65-0.75 0.75-0.85 >0.85 Joint gap <0.1m 0.1-0.4m 0.4-1m 1-3m >3m Bedding gap <0.05m 0.05-0.3m 0.3-1m 1-2m >2m

[0061] 2. Steps for judging the stress influence state of adjacent goaf areas;

[0062] The influence of the square of adjacent goaf areas is judged. According to mining experience, when the working face is squared, stress is concentrated, the mine pressure is strong, and the deformation of the roof and floor is large. This is the key prevention and control stage of mine pressure. If the working face is not squared, the output is 0, the first square is output 1, and the other squares are output 2;

[0063] The first square of the working face: refers to the working face strike length and dip length are equal, that is, the working face advance distance and the working face length are projected on the plane to form an approximate square;

[0064] Goaf square: refers to the working face dip length plus the adjacent goaf dip length equal to the working face strike length, that is, the sum of the working face dip length and the adjacent goaf dip length, and the working face advance distance, projected on the plane is approximately a square;

[0065] 3. Basic top stability judgment steps;

[0066] As the working face advances, the basic roof collapses, a triangular sliding zone is formed above the support, the stability of the working face decreases, the pressure from the working face becomes apparent, and the bearing pressure of each support on the working face increases. Therefore, judging the pressure from the working face is an effective method to judge the collapse of the basic roof.

[0067] Working surface pressure judgment: calculate the real-time bearing pressure of each support on the working surface;

[0068] (1) For 10 consecutive supports, the pressure of more than 5 supports is greater than the opening pressure of the safety valve 40Mpa;

[0069] (2) Except for the support for lowering, moving and lifting, the average pressure of the other supports on the working face is greater than 1.2 times the average pressure of all supports on the working face in the past 10 days;

[0070] (3) There are more than 5 supports with a resistance increase rate > 1Mpa / min in a short period of time;

[0071] (4) The weighted average resistance of each stent in the last cycle is greater than 1.2 times the weighted average resistance of the stent in the last 10 days;

[0072] Meeting both of the above indicators is defined as working face pressure.

[0073] Determination of dynamic load coefficient of working face pressure: dynamic load coefficient = average support pressure / average pressure of all supports on the working face in the past 10 days; dynamic load coefficient > 2 is defined as strong pressure; 1 < dynamic load coefficient < 2 is defined as obvious pressure; future pressure is considered to have a dynamic load coefficient of 1.

[0074] Basic top stability classification: The working surface is classified according to the pressure state and pressure intensity of the working surface (as shown in the following table).

[0075] No pressure Obviously pressure Strong pressure Basic top stability evaluation Stablize More stable Unstable

[0076] 4. Direct top stability judgment steps;

[0077] The stability of the S51 direct roof can be determined by monitoring the broken state of the roof of the working face;

[0078] S52 calculates the initial support force of the working face support to meet the standard;

[0079] S53 monitors the working face supports in real time to detect the occurrence of the "pressure bridge" phenomenon.

[0080] (1) The mean stress of the continuous adjacent e-stage supports is lower than the average stress of the working surface;

[0081] (2) The average stress of m (no more than 6) brackets on the left and right sides of bracket e is greater than the average stress of the working surface;

[0082] (3) The difference between the average stress of the m (no more than 6) brackets and the average stress of the e brackets is greater than 5 MPa;

[0083] (4) The absolute value of the height of the bracket of stage e and the height of the bracket of stage m (no more than 6) is less than 20cm.

[0084] When the above conditions are met, the top plate of the e-stage support is defined as the top plate crushing area.

[0085] Solve the mean support pressure P of the support of stage e 1 , solve the mean support pressure P of all supports on the working surface 2 , crushing coefficient α 1 =P 1 / P 2 , roof crushing rate = e / J, where e is the number of supports in the roof crushing area; J is the total number of supports on the working face; if the roof is not crushed, the roof crushing rate is considered to be 0, and the roof crushing coefficient is 1.

[0086] The broken top plate is classified according to the crushing coefficient, as shown in the following table:

[0087] Stable top plate General broken roof Broken roof Extremely broken roof <![CDATA[Fragmentation coefficient α 1 > other <![CDATA[0.5<α 1 <0.8]]> <![CDATA[0.3<α 1 <0.5]]> <![CDATA[α 1 <0.3]]>

[0088] The comprehensive stability of the working face is evaluated in the following steps:

[0089] S1. Obtain the four indicators of working face evaluation obtained by calculation: roof rock state index, adjacent goaf stress influence state index, basic roof stability state index, and direct roof stability state index.

[0090] S2. Use the entropy method to build an index evaluation system and build 7 roof stability evaluation indicators: rock integrity coefficient, rock joint gap, rock bedding gap, working face square state, working face pressure dynamic load coefficient, roof crushing rate, and roof crushing coefficient.

[0091] S3. Collect relevant data in the laboratory or in current practical applications. The sampling number m should not be too small. Build 7 samples for roof stability evaluation.

[0092] S4. Build the original data matrix of m samples and 7 indicators based on the acquired data.

[0093]

[0094] Among them, X ij Represents the value of the jth evaluation index of the ith sample.

[0095] S5. Eliminate the impact of different dimensions on the evaluation results and standardize various indicators;

[0096] When the larger the indicator is, the more beneficial it is to the development of the system, the positive indicator calculation method is adopted; when the smaller the indicator is, the more beneficial it is to the development of the system, the negative indicator calculation formula is adopted.

[0097] Positive indicators: Negative indicators:

[0098] Among them, X′ ij is the standardized value of the jth indicator of the i-th sample; X j is the jth index value of the i-th sample; X min is the minimum value of the jth index of the i-th sample; X max is the maximum value of the jth index of the i samples;

[0099] S6. Calculate the weight of the i-th sample value under the j-th roof stability evaluation index; the calculation formula is:

[0100]

[0101] Among them, P ij is the proportion of the i-th sample value under the j-th indicator; X′ ij is the standardized value of the jth item of the ith sample; n is the total number of evaluation indicators;

[0102] S7. Calculate the entropy value, and the calculation formula is:

[0103]

[0104] in, e jis the information entropy value of the jth indicator; n is the total number of evaluation indicators; m is the number of samples; P ij is the proportion of the i-th sample value under the j-th indicator;

[0105] S8. Obtain the coefficient of difference, the calculation formula is:

[0106] e j =1-e j ;

[0107] Among them, g j is the coefficient of difference of the j-th indicator; e j is the information entropy value of the j-th indicator;

[0108] S9. Obtain the weight, the calculation formula is:

[0109]

[0110] Among them, W j is the weight of the jth indicator; g j is the coefficient of variation of the jth indicator; m is the number of samples;

[0111] S10. Calculate the roof stability value score, the calculation formula is:

[0112]

[0113] Among them, S i is the roof stability value score of the i-th solution; W j is the weight of the jth indicator of the ith solution; P ij is the proportion of the i-th sample value under the j-th indicator; m is the number of samples;

[0114] S11. Determine the comprehensive stability rating of the working face based on the roof stability value score and empirical analysis method.

[0115] To evaluate the quality of working face support, the steps are as follows:

[0116] S12. Use the entropy method to build an index evaluation system and establish four support quality evaluation indicators: roof stability value score, real-time compliance rate of working face support pressure, real-time opening rate of support safety valve, and support resistance surplus;

[0117] Real-time compliance rate of support pressure at the working face;

[0118] The real-time compliance rate of the support pressure at the working face = the number of supports that meet the pressure standard (pressure greater than 24MPa) / the total number of supports;

[0119] Real-time opening rate of the bracket safety valve;

[0120] Real-time opening rate of bracket safety valve = number of brackets with pressure exceeding limit (pressure greater than rated resistance) / total number of brackets;

[0121] Support resistance margin;

[0122] Support resistance margin = pressure margin (pressure less than 80% of rated resistance) support number / total support number;

[0123] S13, using the entropy method in steps S4 to S9 to calculate and obtain the weights of various indicators of working face support quality;

[0124] S14. Calculate the support quality value score using the obtained weight.

[0125] S15. Based on the support quality value score, rate the support quality based on experience.

[0126] The present invention analyzes all factors, including the development state of basic roof rock joints, the impact of goaf caused by mining technology, the impact of roof pressure, the impact of real-time bearing and roof crushing degree, and the impact of roof surrounding rock stability. From different angles and aspects, the present invention dynamically evaluates the roof stability state of the working face more objectively and accurately, solves the limitations of existing working face stability assessment methods, improves the accuracy of working face stability assessment, and further guarantees the safety of coal mining work.

Claims

1. A dynamic evaluation method for comprehensive stability of working face and surrounding rock support conditions, Features: The following steps are involved: S1. Obtain the roof stratum status index, adjacent goaf stress influence status index, basic roof stability status index, and direct roof stability status index that affect the working face evaluation; S2. The roof stability evaluation system is established through the roof rock state index, the stress influence state index of the adjacent goaf, the basic roof stability state index, and the direct roof stability state index. The roof stability evaluation system includes seven roof stability evaluation indexes, which are: rock mass integrity coefficient, rock mass joint gap, rock mass layer gap, working face square state, working face pressure dynamic load coefficient, roof crushing rate, and roof crushing coefficient; among them, Rock mass integrity coefficient = (rock mass longitudinal wave velocity / rock longitudinal wave velocity in laboratory) 2 ; The square status of the working face is: if the working face is not squared, output 0; if the working face is squared for the first time, output 1; if the working face is squared for multiple times or the goaf of the working face is squared, output 2; Working face pressure dynamic load coefficient = average support pressure / average support pressure of all supports on the working face in the past 10 days; Roof crushing rate = e / J; roof crushing coefficient α 1 =P 1 / P 2 ; Where, e is the number of supports in the roof crushing area; J is the total number of supports on the working surface; P 1 is the average support pressure of the e-stage support; P 2 is the average support pressure of all supports on the working surface; S3, calculate the roof stability value score by entropy method; S4. Establish a working face support strength evaluation system. The working face support strength evaluation system includes four support quality evaluation indicators: roof stability value score, working face support pressure real-time compliance rate, support safety valve real-time opening rate, and support resistance surplus; S5. Calculate the support quality value score by entropy method; S6. Determine the comprehensive stability rating of the working face through roof stability value score analysis; determine the surrounding rock support quality rating through support quality value score analysis.

2. The method for dynamic assessment of comprehensive stability of working face and surrounding rock support conditions as claimed in claim 1, Features: In step S2, when obtaining the rock mass joint gap, firstly, drilling is performed in the selected working surface area, and then a borehole peep instrument is used to obtain a rock mass borehole image, and then the rock mass joint gap is obtained by observing the rock mass borehole image.

3. The method for dynamic assessment of comprehensive stability of working face and surrounding rock support conditions as claimed in claim 2, Features: In step S2, when obtaining the rock layer gap, first use a borehole viewer to obtain a rock hole image, then determine the position of each rock layer based on the color, shape, and particle size of the rock in the rock hole image, and finally determine the rock layer gap based on the single layer thickness of the rock layer.

4. The method for dynamic assessment of comprehensive stability of working face and surrounding rock support conditions as claimed in claim 1, Features: In step S3, calculating the roof stability value score by entropy method includes the following steps: S31. Collect m samples in the laboratory or in actual application; S32, constructing the original data matrix of m samples and various roof stability evaluation indicators; obtaining: Among them, X ij represents the value of the j-th roof stability evaluation index of the i-th sample; S33, eliminate the influence of different dimensions on the evaluation results, and standardize the various roof stability evaluation indicators; obtain: When the larger the indicator is, the more beneficial it is to the development of the system, the positive indicator calculation formula is adopted; the calculation formula is: Positive indicators: When the smaller the indicator is, the more beneficial it is to the development of the system, the negative indicator calculation formula is adopted: The calculation formula is: Negative indicators: Among them, X′ ij is the standardized value of the jth indicator of the i-th sample; X j is the jth index value of the i-th sample; X min is the minimum value of the jth index of the i-th sample; X max is the maximum value of the jth index of the i samples; S34, calculate the proportion of the i-th sample value under the j-th roof stability evaluation index; the calculation formula is: Among them, P ij is the proportion of the i-th sample value under the j-th indicator; X′ ij is the standardized value of the i-th sample; n is the total number of evaluation indicators; S35. Calculate the entropy value, and the calculation formula is: in, e j is the information entropy value of the jth indicator; n is the total number of evaluation indicators; m is the number of samples; P ij is the proportion of the i-th sample value under the j-th indicator; S36. Obtain the coefficient of difference, the calculation formula is: g j =1-e j ; Among them, g j is the coefficient of difference of the j-th indicator; e j is the information entropy value of the j-th indicator; S37, obtain the weight, the calculation formula is: Among them, W j is the weight of the jth indicator; g j is the coefficient of variation of the jth indicator; m is the number of samples; S38. Calculate the roof stability value score, the calculation formula is: Among them, S i is the roof stability value score of the i-th solution; W j is the weight of the jth indicator of the ith solution; P ij is the proportion of the i-th sample value under the j-th indicator; m is the number of samples.

5. The method for dynamic evaluation of comprehensive stability of working face and surrounding rock support conditions as claimed in claim 4, Features: In step S4, the real-time compliance rate of the working face support pressure = the number of supports that meet the pressure standard / the total number of supports; the real-time opening rate of the support safety valve = the number of supports that exceed the pressure limit / the total number of supports; the support resistance surplus = the number of supports with surplus pressure / the total number of supports.

6. The method for dynamic assessment of comprehensive stability of working face and surrounding rock support conditions as claimed in claim 5, Features: In step S5, calculating the support quality value score by the entropy method includes the following steps: S51. Calculate the weight of each support quality evaluation index using the entropy method; S52. The support quality value score is obtained by weighting each support quality evaluation index.

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