A comprehensive evaluation method of goaf stability combined with numerical simulation method

Abstract

The application belongs to the technical field of mining, and particularly relates to a goaf stability comprehensive evaluation method combined with a numerical simulation method, which comprises the following steps: S1, initially determining a first influencing factor of goaf stability, and constructing a numerical model of an orthogonal test scheme; S2, determining the first influencing factor of goaf stability; S3, obtaining a second influencing factor of goaf stability; S4, constructing a goaf stability evaluation model, and determining the weight of the second influencing factor of goaf stability; S5, according to the goaf stability evaluation model of S4 and the weight of the second influencing factor of goaf stability, determining a goaf stability fuzzy comprehensive evaluation matrix; and S6, according to the goaf stability fuzzy comprehensive evaluation matrix, obtaining an evaluation matrix of the second influencing factor of goaf stability, and determining the level of goaf stability. The application analyzes the sensitivity of the influencing factors of goaf stability by combining the numerical simulation method, and improves the accuracy of the evaluation of goaf stability.

Description

Technical Field

[0001] This invention relates to the field of mining technology, and in particular to a comprehensive evaluation method for the stability of goaf areas that combines numerical simulation methods. Background Technology

[0002] Underground mining of metal mines often leaves behind numerous goafs after stope extraction. Especially before the widespread adoption of backfilling methods and related regulations, many small and medium-sized mines in China had large amounts of untreated goafs. Once these goafs become unstable, roof collapses can create shock waves and other hazards, potentially leading to large-scale underground ground pressure disasters, equipment damage, casualties, and sudden surface subsidence. Therefore, conducting stability assessment studies on underground goafs in metal mines is crucial for providing a basis for the rational and orderly management of goafs and the selection of goaf treatment methods, and is of great significance for mine safety and environmental protection.

[0003] Numerous factors influence the stability of goaf areas within mining districts. Existing technologies often employ mathematical methods to comprehensively evaluate the stability of goaf areas. However, these mathematical methods for stability evaluation involve numerous evaluation factors, leading to a cumbersome evaluation process. Furthermore, there is insufficient objective evaluation of the weights of the comprehensive stability evaluation factors, relying more on the subjective determination of researchers and lacking a scientific basis for weight determination.

[0004] Therefore, this application provides a comprehensive evaluation method for goaf stability that combines numerical simulation methods. Summary of the Invention

[0005] In view of the above-mentioned shortcomings and deficiencies of the existing technology, the present invention provides a comprehensive evaluation method for goaf stability that combines numerical simulation methods. This solves the technical problems of existing technologies having many factors for comprehensive evaluation of goaf stability, which leads to a complicated evaluation process; secondly, the objective evaluation of the weights of stability evaluation factors is insufficient, and they rely more on subjective human determination, lacking a scientific basis for weight determination.

[0006] To achieve the above objectives, this invention provides a comprehensive evaluation method for goaf stability combining numerical simulation methods, the method comprising:

[0007] S1. Preliminarily determine the primary influencing factor on the stability of the goaf, construct an orthogonal test scheme for goaf stability analysis, and establish a numerical model for the orthogonal test scheme;

[0008] In S1, the primary factors influencing the stability of the goaf include: the angle between the long axis of the goaf and the direction of the maximum principal stress, the uniaxial compressive strength, the rock quality index RQD value, the length of the goaf, the joint spacing, the height of the goaf, the width of the goaf, the width of the pillar, the depth of the goaf, the water inflow, and Poisson's ratio.

[0009] S2. Assign rock mechanics parameters to the numerical model of the orthogonal test scheme, conduct simulation analysis, determine the primary influencing factor on the stability of the goaf, and statistically obtain the simulation results of the orthogonal test scheme.

[0010] In S2, a numerical model of an orthogonal test scheme for goaf stability analysis is constructed, and the rock mechanics parameters of the corresponding scheme are assigned to the model to simulate and analyze each scheme.

[0011] S3. Using range analysis, determine the range value of the first influencing factor on the stability of the goaf, rank the sensitivity of the first influencing factor on the stability of the goaf, eliminate the first influencing factor on the stability of the goaf with less influence, and then obtain the second influencing factor on the stability of the goaf.

[0012] In S3, using range analysis, a large range value of the factors affecting the stability of the goaf indicates a high degree of influence, and vice versa.

[0013] Based on the range values, the primary influencing factors on the stability of the goaf are ranked as follows: angle between the long axis of the goaf and the direction of the maximum principal stress > uniaxial compressive strength > rock quality index RQD value > goaf length > joint spacing > goaf height > goaf width > pillar width > goaf burial depth > water inflow > Poisson's ratio.

[0014] The method for eliminating the primary influencing factors of goaf stability with a minor impact is as follows: compare the range of each primary influencing factor of goaf stability with the largest range. If the ratio is less than 1 / 3, the primary influencing factor of goaf stability is considered to have a minor impact on goaf stability and is therefore eliminated.

[0015] In S3, Poisson's ratio, water inflow, and goaf depth are removed from the first influencing factors of goaf stability. Then, the angle between the long axis of the goaf and the direction of the maximum principal stress, uniaxial compressive strength, rock quality index RQD value, goaf length, joint spacing, goaf height, pillar width, and goaf width are taken as the second influencing factors of goaf stability.

[0016] S4. Using the analytic hierarchy process, construct a goaf stability evaluation model. Based on the second influencing factor of goaf stability determined in S3 and its corresponding range value, determine the weight of the second influencing factor of goaf stability.

[0017] In S4, the identified second influencing factors on goaf stability are classified, and a set U of the second influencing factors on goaf stability is established, let U = {u1 (angle between the long axis of the goaf and the direction of the maximum principal stress), u2 (uniaxial compressive strength), u3 (rock quality index RQD value), u4 (goaf length), u5 (joint surface spacing), u6 (goaf height), u7 (goaf width), u8 (pillar width)}.

[0018] S5. Based on the S4 goaf stability evaluation model and the weight of the second influencing factor on goaf stability, determine the fuzzy comprehensive evaluation matrix for goaf stability.

[0019] The mapping function for transforming the stability range of the goaf is constructed as follows:

[0020] ;

[0021] In the formula, These are the measured values ​​of quantitative indicators; This represents the upper limit of the evaluation range for the stability level of the goaf, corresponding to the measured value of the second influencing factor index on the stability of the goaf. This is the lower limit of the evaluation range for the stability level of the goaf, corresponding to the measured value of the second influencing factor index on the stability of the goaf. This is the upper limit of the quantitative value range of the goaf stability level corresponding to the second influencing factor indicator of goaf stability; This is the lower limit of the quantitative value range of the goaf stability level corresponding to the second influencing factor index of goaf stability.

[0022] In S5, the membership function is constructed. for

[0023] ;

[0024] ;

[0025] ;

[0026] ;

[0027] In the formula, δ is the neighborhood value centered at the midpoint of the interval within the quantitative value range of the evaluation level. The membership degree within the above neighborhood range is calculated by the mapping function and membership function of the goaf stability value range transformation. The membership degree of the measured value of the second influencing factor index of goaf stability belongs to the four evaluation levels, and the goaf stability fuzzy comprehensive evaluation matrix R is constructed.

[0028] Construct the fuzzy comprehensive evaluation matrix R for the stability of the goaf:

[0029] ;

[0030] In the formula, Measured values ​​of quantitative indicators Membership degree of the evaluation level.

[0031] S6. Based on the fuzzy comprehensive evaluation matrix of goaf stability, the evaluation matrix of the second influencing factor of goaf stability is obtained, and then the stability level of goaf is determined.

[0032] The evaluation matrix of the second influencing factor on the stability of the goaf is obtained by evaluating the second influencing factor on the stability of the goaf in turn. for:

[0033] ;

[0034] Calculate the sensitivity ranking and the evaluation matrix of the second influencing factor on the stability of the goaf. Maximum eigenvalue =7.96, and the corresponding eigenvector X is:

[0035] ;

[0036] The desired eigenvector X represents the sensitivity ranking of the second influencing factor on goaf stability. The weight coefficients of the second influencing factor on goaf stability are obtained through normalization of the eigenvector, i.e., the weight vector C of the second influencing factor on goaf stability.

[0037] ;

[0038] Once the weight vector C of the second influencing factor on the stability of the goaf and the fuzzy comprehensive evaluation matrix R are determined, a fuzzy linear transformation is performed on R to transform the weight vector C of the second influencing factor on the stability of the goaf into a fuzzy subset B on the evaluation set V:

[0039] ;

[0040] In the formula, “◦” is the composition operator of the weight vector C of the second influencing factor of goaf stability and the fuzzy comprehensive evaluation matrix R of goaf stability;

[0041] Since all secondary influencing factors affect the stability of goaf areas, a weighted average model is adopted. The fuzzy comprehensive evaluation of goaf stability first obtains the maximum value of the fuzzy subset B vector on the comment set V based on the principle of maximum membership. The value of i ranges from 1 to 4;

[0042] according to The overall evaluation results are used to determine the rating;

[0043] Then, the stability level of the goaf is used to quantify the score. membership degree The weighting coefficient is the quantitative score of the stability level of the goaf. The weighted average of these values ​​is used as the quantitative result of the overall evaluation level (FCA), i.e.:

[0044] ;

[0045] The stability level of the goaf can be determined based on the quantitative result of the comprehensive evaluation level (FCA).

[0046] The beneficial effects of this invention are:

[0047] This invention provides a comprehensive evaluation method for goaf stability that combines numerical simulation. By analyzing the sensitivity of goaf stability influencing factors through orthogonal experiments and numerical simulation, factors with minor impact on goaf stability are eliminated. This ensures the rationality and accuracy of goaf stability evaluation while simplifying the evaluation process.

[0048] Furthermore, rock mechanics theory and criteria are adopted in numerical simulation to transform the influencing factors of goaf stability into rock mechanics parameters, thereby achieving a quantitative assessment of the influencing factors of goaf stability. The sensitivity ranking of each goaf stability influencing factor is obtained through numerical simulation and orthogonal analysis, and weights are assigned to the influencing factors of goaf stability, thus avoiding the subjectivity of the goaf stability evaluation left after mining and improving the scientific nature of the comprehensive evaluation and the accuracy of the evaluation results. Attached Figure Description

[0049] Figure 1 This is a flowchart of the comprehensive evaluation method for goaf stability combining numerical simulation methods according to the present invention. Detailed Implementation

[0050] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present invention can be understood more clearly and thoroughly, and that the scope of the present invention can be fully conveyed to those skilled in the art.

[0051] Embodiments of the present invention provide a comprehensive evaluation method for goaf stability combining numerical simulation methods, such as... Figure 1 As shown, the specific steps include:

[0052] S1. Preliminarily determine the primary influencing factor on the stability of the goaf and construct a numerical model for the orthogonal test scheme;

[0053] Numerous factors influence the stability of goaf areas, including uniaxial compressive strength of rock, rock quality index RQD, joint spacing, rock mass integrity coefficient, Poisson's ratio, volume joint number, structural plane occurrence, groundwater, goaf width, goaf length, goaf burial depth, goaf height, height-to-span ratio, goaf layout and principal stress direction, and pillar width between adjacent goaf areas.

[0054] This embodiment identifies the following 11 factors as the primary influencing factors for goaf stability: uniaxial compressive strength, rock quality index RQD value, water inflow, joint spacing, Poisson's ratio, goaf depth, goaf width, goaf length, goaf height, pillar width, and the angle between the goaf's long axis and the direction of the maximum principal stress. These 11 factors are used as the primary influencing factors for goaf stability. An L27 (3^13) orthogonal array is employed, containing 27 experiments. Each primary influencing factor for goaf stability has 3 levels, resulting in 13 primary influencing factors for goaf stability, including 2 blank factors.

[0055] Specifically, the orthogonal schemes for numerical simulation of goaf stability are shown in Table 1 below:

[0056] Table 1. Orthogonal schemes for numerical simulation of goaf stability

[0057]

[0058] Hoek-Brown rock mass failure criterion expression:

[0059] (1)

[0060] In the formula, The maximum principal stress at rock mass failure is expressed in MPa. The minimum principal stress at rock mass failure, expressed in MPa; denoted as uniaxial compressive strength of rock, in MPa; m is a dimensionless coefficient representing the hardness of the rock mass; s is a dimensionless coefficient representing the degree of rock mass fragmentation.

[0061] The dimensionless coefficient m for the hardness of rock mass is calculated using the following formula:

[0062] (2)

[0063] The dimensionless coefficient s for the degree of rock mass fracturing is calculated using the following formula:

[0064] (3)

[0065] In the formula, The Hoek-Brown constant for the rock mass;

[0066] The calculation is based on existing technology. Specifically, it is a comprehensive evaluation of rock mass classification indicators based on rock strength, rock quality index RQD value, joint spacing and groundwater influence. The results are obtained by taking values ​​from the rock mechanics classification table of jointed rock masses and combining them with those from Table 3.

[0067] when When = 0, the tensile strength of the rock mass is obtained from the Hoek-Brown rock mass failure criterion expression. :

[0068] (4)

[0069] In the formula, The tensile strength of the rock mass is expressed in MPa. denoted as uniaxial compressive strength of rock, in MPa; m is a dimensionless coefficient representing the hardness of the rock mass; s is a dimensionless coefficient representing the degree of rock mass fragmentation.

[0070] The Hoek-Brown rock mass failure criterion provides the elastic modulus of the rock mass. Relationship with RMR:

[0071] (5)

[0072] In the formula, The elastic modulus of the rock mass is expressed in GPa. The uniaxial compressive strength of rock is expressed in MPa.

[0073] The Mohr-Coulomb rock mass failure criterion states that the maximum principal stress at which the rock mass fails is considered to be... Minimum principal stress at rock mass failure There is a linear relationship between them:

[0074] (6)

[0075] In the formula, The maximum principal stress at rock mass failure is expressed in MPa. The rock mass compressive strength is expressed in MPa. is the minimum principal stress at rock mass failure, in MPa; k is the linear slope. .

[0076] When 0 < <0.25 hour, and The rock mass compressive strength is obtained by regressing equation (6) to satisfy the Hoek-Brown rock mass failure criterion expression. and k.

[0077] In addition, the internal friction angle of the rock mass Calculated by the following formula:

[0078] (7)

[0079] In the formula, The internal friction angle of the rock mass is given in degrees; k is the linear slope. ;

[0080] Cohesion of rock mass It can be calculated using the following formula:

[0081] (8)

[0082] In the formula, The cohesion of the rock mass is expressed in MPa. The rock mass compressive strength is expressed in MPa; k is the linear slope. ;

[0083] Assuming the surrounding rock of the goaf is limestone with slightly rough joint surfaces and a width of <1mm, and the joint surface rock is weak, the corresponding RMR parameters can be obtained from Table 2 by referring to the rock mass quality data of the numerical simulation orthogonal test scheme for the stability of the goaf in Table 1. Then, the rock mass mechanical parameters of each of the 27 schemes can be calculated using the above formulas (1)-(8), as shown in Table 2.

[0084] Table 2 Numerical simulation parameters for goaf stability

[0085]

[0086] S2. A numerical model for the orthogonal numerical simulation test of goaf stability was constructed using FLAC3D software. The rock mechanics parameters from the orthogonal numerical simulation test of goaf stability in Table 1 were assigned to the corresponding model values. Based on the existing Matthews stability diagram, the stability of the goaf sidewalls is higher than that of the roof. Therefore, the vertical displacement of the roof was used as a statistical analysis index. The numerical simulation of goaf stability in Table 1 was orthogonally analyzed, and the vertical displacement of the goaf roof was statistically analyzed as shown in Table 3.

[0087] Table 3. Statistics of roof displacement in numerical simulation scheme for goaf stability.

[0088]

[0089] S3. In this embodiment, the roof displacement is selected, and the range value of the rock mechanical parameters is determined by the range analysis method. That is, the range value of the first influencing factor of the stability of the goaf is calculated by the roof displacement, as shown in Table 4.

[0090] Table 4. Range values ​​of the primary influencing factor on goaf stability due to roof displacement.

[0091]

[0092] Using range analysis, a large range value for a rock mechanical parameter indicates a high degree of influence of that parameter, and vice versa.

[0093] Based on the range values, the primary influencing factors on goaf stability are ranked as follows: angle between the goaf's long axis and the direction of the maximum principal stress > uniaxial compressive strength > rock quality index (RQD value) > goaf length > joint spacing > goaf height > goaf width > pillar width > goaf burial depth > water inflow > Poisson's ratio.

[0094] The extreme value of each influencing factor in the first influencing factor is compared with the maximum extreme value in the first influencing factor. The influencing factor with a ratio less than 1 / 3 is considered to have a smaller impact and is eliminated. Based on the above elimination method, Poisson's ratio, water inflow, and goaf burial depth are eliminated from the first influencing factors of goaf stability. Then, the angle between the long axis of the goaf and the direction of the maximum principal stress, uniaxial compressive strength, rock quality index RQD value, goaf length, joint spacing, goaf height, pillar width, and goaf width are identified as the second influencing factors of goaf stability.

[0095] S4. Using the analytic hierarchy process, construct a goaf stability evaluation model. Based on the second influencing factor of goaf stability determined in S3 and its corresponding range value, determine the weight of the second influencing factor of goaf stability.

[0096] Classify the second influencing factors of goaf stability and establish a set U of the second influencing factors of goaf stability, let U = {u1 (angle between the long axis of the goaf and the direction of the maximum principal stress), u2 (uniaxial compressive strength), u3 (rock quality index RQD value), u4 (goaf length), u5 (joint surface spacing), u6 (goaf height), u7 (goaf width), u8 (pillar width)};

[0097] The stability level classification of the second influencing factor on goaf stability is based on the engineering rock mass stability classification, dividing the second influencing factor on goaf stability into 4 stability levels, namely V={V1(stable)}. V2 (basically stable) V3 (Unstable) V4 (unstable) )}.

[0098] Among them, V1 (stable) V2 indicates that no remediation measures or monitoring are required for the goaf area; V2 (basically stable) This indicates that the goaf area needs to be treated and monitored to ensure safe production within its affected area; V3 (understable) This indicates that measures need to be taken and monitoring implemented in the goaf area, and emergency plans should be developed; V4 (unstable) This indicates that measures must be taken immediately in the goaf area and monitoring should be strengthened, and personnel and equipment within the affected area should be evacuated immediately.

[0099] The evaluation level of the second influencing factor on the stability of the goaf is shown in Table 5 below.

[0100] Table 5. Stability Levels of the Second Influencing Factor on Goaf Stability

[0101]

[0102] When determining the membership degree of the four evaluation levels of the second influencing factor on the stability of the goaf, it is first necessary to convert the measured values ​​of the quantitative indicators into values ​​within the quantitative range. This facilitates the unified construction of the membership function and the final comprehensive evaluation of the stability of the goaf.

[0103] S5. Based on the S4 goaf stability evaluation model and the weights of rock mechanics parameters, determine the comprehensive evaluation matrix for goaf treatment.

[0104] Based on the results of S4, the mapping function for the stability range transformation of the goaf is constructed as follows:

[0105] (9)

[0106] (10)

[0107] In the formula, These are the measured values ​​of quantitative indicators; This represents the upper limit of the evaluation range for the stability level of the goaf, corresponding to the measured value of the second influencing factor index on the stability of the goaf. This is the lower limit of the evaluation range for the stability level of the goaf, corresponding to the measured value of the second influencing factor index on the stability of the goaf. This is the upper limit of the quantitative value range of the goaf stability level corresponding to the second influencing factor indicator of goaf stability; This is the lower limit of the quantitative value range of the goaf stability level corresponding to the second influencing factor index of goaf stability;

[0108] Formula (9) in the mapping function for the stability range transformation of goaf areas is: The larger the value, the more stable the goaf; formula (10) is The larger the area, the more unstable the goaf.

[0109] Constructed membership function for

[0110] (11)

[0111] (12)

[0112] (13)

[0113] (14)

[0114] In the formula, δ is the neighborhood value centered at the midpoint of the interval within the quantitative value range of the evaluation level, and the membership degree within the neighborhood is 1.

[0115] The membership degree of each evaluation level to which the measured value of the second influencing factor evaluation index of goaf stability belongs can be calculated by formulas (9)-(14), that is, the fuzzy comprehensive evaluation matrix R of goaf stability can be constructed.

[0116] (15)

[0117] In the formula, The second influencing factor on the stability of goaf areas Membership degree with evaluation level.

[0118] S6. Based on the fuzzy comprehensive evaluation matrix of goaf stability, the evaluation matrix of factors affecting goaf stability is obtained, and then the stability level of goaf is determined.

[0119] After constructing the fuzzy comprehensive evaluation matrix R for goaf stability, it is necessary to determine the weights of factors u1 to u8. The influence of factors u1 to u8 on goaf stability varies in the evaluation, therefore, it is necessary to determine the weights of the u1 to u8 factor indicators.

[0120] In this embodiment, the evaluation objective of the fuzzy comprehensive evaluation matrix for goaf stability is the stability of the goaf. Therefore, the evaluation objective is determined as the second influencing factor of goaf stability, i.e., U = {u1 (angle between the long axis of the goaf and the direction of the maximum principal stress), u2 (uniaxial compressive strength), u3 (RQD value of rock quality index), u4 (length of goaf), u5 (joint surface spacing), u6 (height of goaf), u7 (width of goaf), u8 (width of pillar)}. The comprehensive evaluation method for goaf stability in this embodiment does not use human factors for assignment, but rather determines the stability by the ratio of the range values ​​between two influencing factors of goaf stability, as shown in Table 4, which represents the range value of the first influencing factor of goaf stability for roof displacement. This setting effectively avoids the subjectivity of human factors in assigning values ​​to influencing factors of goaf stability.

[0121] For example, comparing u1 (the angle between the major axis of the goaf and the direction of the maximum principal stress) with u2 (uniaxial compressive strength), the ratio is 1.2. Therefore, the angle between the major axis of the goaf and the direction of the maximum principal stress is more important. Thus, the fuzzy comprehensive evaluation matrix for goaf stability is:

[0122] (16)

[0123] Calculate the evaluation matrix of the second influencing factor on the stability of the goaf. The largest eigenvalue λ max =7.96, and the corresponding eigenvector X is:

[0124] (17)

[0125] The obtained eigenvector X represents the sensitivity ranking of the second influencing factor on goaf stability. The weight coefficients of the second influencing factor on goaf stability are obtained through normalization of the eigenvector, i.e., the weight vector C of the second influencing factor on goaf stability.

[0126] (18)

[0127] Once the weight vector C of the second influencing factor on goaf stability and the fuzzy comprehensive evaluation matrix R of goaf stability are determined, a fuzzy linear transformation is performed on the fuzzy comprehensive evaluation matrix R of goaf stability to transform the weight vector C of the second influencing factor on goaf stability into a fuzzy subset B on the evaluation set V:

[0128] (19)

[0129] In the formula, The operator is used to combine the weight vector C of the second influencing factor on the stability of the goaf with the fuzzy comprehensive evaluation matrix R of the stability of the goaf. Since all the second influencing factors on the stability of the goaf affect the stability of the goaf, a weighted average model is adopted.

[0130] Then, the stability level of the goaf is used to quantify the score. membership degree As the weighting coefficients, take each V ai The weighted average is used as the quantitative result of the overall evaluation level (FCA), that is:

[0131] (20)

[0132] Based on the quantitative result of the comprehensive evaluation level (FCA), the stability level of the goaf under the evaluation conditions is obtained.

[0133] Example calculation:

[0134] The factor set U for the second influencing factor on the stability of the goaf in a certain mine is U={10, 40, 60, 30, 85, 25, 8, 22};

[0135] The mapping value f(u) is calculated based on equations (9) and (10) of the mapping function for the stability range transformation of the goaf. i ={0.833, 0.4, 0.6, 0.6667, 0.6750, 0.3750, 0.5, 0.7750};

[0136] Then, according to equations (11) to (14) in sequence, that is, the membership function A j (f(u i The fuzzy comprehensive evaluation matrix R for the stability of the goaf area of ​​the mine was calculated as follows:

[0137] ;

[0138] By performing a fuzzy linear transformation on R, that is, by using equations (16)-(18) to transform the weight vector C of the second influencing factor of goaf stability into a fuzzy subset B on the comment set V, equation (19) is used. Substituting the fuzzy comprehensive evaluation matrix R of the goaf stability of the above mine into equation (19), we can obtain B=[0.24667,0.45833,0.295,0]; Substituting the value of B into the quantitative result FCA of the comprehensive evaluation level in equation (20), we obtain FCA=0.61292;

[0139] Based on the B value and FCA value mentioned above, the goaf of the mine can be determined to be basically stable at level II.

[0140] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make modifications, alterations, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A comprehensive evaluation method for goaf stability combining numerical simulation, characterized in that, include: S1. Preliminarily determine the primary influencing factor on the stability of the goaf, construct an orthogonal test scheme for goaf stability analysis, and construct a numerical model for the orthogonal test scheme; S2. Assign rock mechanics parameters to the numerical model of the orthogonal test scheme, conduct numerical simulation analysis, determine the primary influencing factor on the stability of the goaf, and statistically obtain the simulation results of the orthogonal test scheme. S3. Using range analysis, determine the range value of the first influencing factor on the stability of the goaf, rank the sensitivity of the first influencing factor on the stability of the goaf, eliminate the first influencing factor on the stability of the goaf with less influence, and then obtain the second influencing factor on the stability of the goaf. S4. Using the analytic hierarchy process, construct a goaf stability evaluation model. Based on the second influencing factor of goaf stability determined in S3 and its corresponding range value, determine the weight of the second influencing factor of goaf stability. In S4, the selected second influencing factors of goaf stability are classified and a set U of the second influencing factors of goaf stability is established, let U = {u1 (angle between the long axis of the goaf and the direction of the maximum principal stress), u2 (uniaxial compressive strength), u3 (rock quality index RQD value), u4 (goaf length), u5 (joint surface spacing), u6 (goaf height), u7 (goaf width), u8 (pillar width)}; S5. Based on the S4 goaf stability evaluation model and the weight of the second influencing factor on goaf stability, determine the fuzzy comprehensive evaluation matrix for goaf stability. The mapping function for transforming the stability range of the goaf is constructed as follows: ； In the formula, These are the measured values ​​of quantitative indicators; This represents the upper limit of the evaluation range for the stability level of the goaf, corresponding to the measured value of the second influencing factor index on the stability of the goaf. This is the lower limit of the evaluation range for the stability level of the goaf, corresponding to the measured value of the second influencing factor index on the stability of the goaf. This is the upper limit of the quantitative value range of the goaf stability level corresponding to the second influencing factor indicator of goaf stability; This is the lower limit of the quantitative value range of the goaf stability level corresponding to the second influencing factor index of goaf stability; In S5, the membership function is constructed. for: ； ； ； ； In the formula, δ is the neighborhood value centered at the midpoint of the interval within the quantitative value range of the evaluation level. The membership degree within the neighborhood range is calculated by the mapping function and membership function of the goaf stability value range transformation to determine the membership degree of the measured value of the second influencing factor index of goaf stability to the four evaluation levels, and the goaf stability fuzzy comprehensive evaluation matrix R is constructed. The fuzzy comprehensive evaluation matrix R for the stability of the goaf area: ； In the formula, Indicators Membership degree with evaluation level; S6. Based on the fuzzy comprehensive evaluation matrix of goaf stability, the evaluation matrix of the second influencing factor of goaf stability is obtained, and then the stability level of goaf is determined.

2. The comprehensive evaluation method for goaf stability combining numerical simulation as described in claim 1, characterized in that: In S1, the first influencing factors on the stability of the goaf include: the angle between the long axis of the goaf and the direction of the maximum principal stress, the uniaxial compressive strength, the rock quality index RQD value, the length of the goaf, the joint spacing, the height of the goaf, the width of the goaf, the width of the pillar, the depth of the goaf, the water inflow, and Poisson's ratio.

3. The comprehensive evaluation method for goaf stability combining numerical simulation as described in claim 1, characterized in that, In S2, an orthogonal test scheme numerical model for goaf stability analysis is constructed, rock mechanics parameters are assigned to the orthogonal test scheme numerical model for goaf stability analysis, and the orthogonal test scheme for goaf stability analysis is simulated and analyzed.

4. The comprehensive evaluation method for goaf stability combining numerical simulation as described in claim 1, characterized in that, In S3, according to the range analysis method, a large range value of the factors affecting the stability of the goaf indicates a high degree of influence, and vice versa. Based on the range values, the primary influencing factors on goaf stability are ranked as follows: angle between the goaf's long axis and the direction of the maximum principal stress > uniaxial compressive strength > rock quality index RQD value > goaf length > joint spacing > goaf height > goaf width > pillar width > goaf burial depth > water inflow > Poisson's ratio.

5. The comprehensive evaluation method for goaf stability combining numerical simulation as described in claim 4, characterized in that, In S3: The method for eliminating the first influencing factors of goaf stability with a relatively small impact is as follows: compare the range value of each first influencing factor of goaf stability with the largest range value, and the first influencing factors of goaf stability with a ratio of less than 1 / 3 are the first influencing factors of goaf stability with a relatively small impact, and the first influencing factors of goaf stability with a relatively small impact are eliminated. In S3, Poisson's ratio, water inflow, and goaf depth are removed from the first influencing factors of goaf stability. Then, the angle between the long axis of the goaf and the direction of the maximum principal stress, uniaxial compressive strength, rock quality index RQD value, goaf length, joint spacing, goaf height, pillar width, and goaf width are taken as the second influencing factors of goaf stability.

6. The comprehensive evaluation method for goaf stability combining numerical simulation as described in claim 1, characterized in that, In step S6, an evaluation matrix for the second influencing factor on the stability of the goaf is constructed. for: ； Based on the sensitivity ranking, calculate the evaluation matrix P of the second influencing factor on the stability of the goaf. T Maximum eigenvalue =7.96, and the corresponding eigenvector X is: ； The obtained feature vector X represents the sensitivity ranking of the second influencing factor on goaf stability. By normalizing the feature vector X, the weight coefficients of the second influencing factor on goaf stability are obtained, i.e., the weight vector C of the second influencing factor on goaf stability. ； Once the weight vector C of the second influencing factor on goaf stability and the fuzzy comprehensive evaluation matrix R of goaf stability are determined, the weight vector C of the second influencing factor on goaf stability is transformed into a fuzzy subset B on the evaluation set V by performing a fuzzy linear transformation on the fuzzy comprehensive evaluation matrix R of goaf stability. The specific transformation process is as follows: ； In the formula, B is a fuzzy subset on the comment set V; C is the weight vector of the second influencing factor on the stability of the goaf; and R is the fuzzy comprehensive evaluation matrix for the stability of the goaf. The operator is used to combine the weight vector C of the second influencing factor on the stability of the goaf with the fuzzy comprehensive evaluation matrix R of the stability of the goaf. The fuzzy comprehensive evaluation of goaf stability can first be performed by obtaining the maximum value of the fuzzy subset B vector on the comment set V based on the principle of maximum membership. The value of i ranges from 1 to 4; according to The results determine the stability level of the goaf; The stability level of the goaf is quantified by a score. membership degree The weighting coefficient is the quantitative score of the stability level of each goaf. The weighted average of these values ​​is used as the quantitative result (FCA) of the goaf stability level, i.e.: ； The stability level of the goaf is obtained based on the quantitative result of the goaf stability level (FCA).

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