Goaf stability comprehensive evaluation method combined with numerical simulation method

Abstract

The invention relates to the technical field of mining, in particular to a goaf stability comprehensive evaluation method combined with a numerical simulation method, which comprises the following steps: S1, preliminarily determining a first influence factor of goaf stability, and constructing a numerical model of an orthogonal test scheme; s2, determining a first influence factor of the stability of the goaf; s3, obtaining a second influence factor of the stability of the goaf; s4, constructing a goaf stability evaluation model, and determining the weight of a second influence factor of goaf stability; s5, determining a goaf stability fuzzy comprehensive evaluation matrix according to the goaf stability evaluation model and the weight of the goaf stability second influence factor; and S6, according to the goaf stability fuzzy comprehensive evaluation matrix, obtaining an evaluation matrix of the second influence factor of the goaf stability, and determining the level of the goaf stability. According to the method, the sensitivity of goaf stability influence factors is analyzed by combining a numerical simulation method, and the accuracy of goaf stability evaluation is improved.

Description

Technical Field

[0001] The present invention relates to the field of mining technology, and in particular to a comprehensive evaluation method for goaf stability combined with a numerical simulation method. Background Art

[0002] Underground mining of metal mines often leaves behind a large number of goafs after the mine chambers are mined. This is especially true before the adoption of the backfill method and the popularization of relevant regulations. Some small and medium-sized mines in China left behind a large number of goafs that were not promptly addressed. Once the goafs become unstable, the roof collapses, creating hazards such as impact waves. In severe cases, this can cause large-scale underground ground pressure disasters, equipment damage, casualties, sudden surface collapse, and other safety accidents. Therefore, conducting research on the stability evaluation of underground goafs in metal mines provides a basis for the rational and orderly management of goafs and the selection of goaf treatment methods, which is of great significance to mine safety production and environmental protection.

[0003] There are many factors that affect the stability of goafs within mining areas. Existing technologies often use mathematical methods to comprehensively evaluate the stability of goafs. However, these mathematical methods for stability evaluation contain many evaluation factors, which makes the evaluation process cumbersome. Secondly, there is insufficient objective evaluation of the weights of comprehensive stability evaluation factors, which rely more on the subjective determination of researchers and lack a scientific basis for weight determination.

[0004] To this end, this application provides a comprehensive evaluation method for goaf stability combined with numerical simulation methods. Summary of the Invention

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a comprehensive evaluation method for the stability of goaf combined with a numerical simulation method, thereby solving the technical problems that the prior art has many comprehensive evaluation factors for the stability of goaf, resulting in a cumbersome evaluation process; secondly, there is insufficient objective evaluation of the weights of stability evaluation factors, which rely more on human subjective determination and lacks a scientific basis for weight determination.

[0006] In order to achieve the above object, the present invention provides a comprehensive evaluation method for goaf stability combined with a numerical simulation method, the method comprising: S1. Preliminarily determine the primary influencing factor of goaf stability, construct an orthogonal test scheme for goaf stability analysis, and establish a numerical model for the orthogonal test scheme; In S1, the first influencing factors of goaf stability include: 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 surface spacing, goaf height, goaf width, pillar width, goaf burial depth, water inflow, and Poisson's ratio.

[0007] S2. Assign rock mechanics parameters to the numerical model of the orthogonal test scheme, conduct simulation analysis, determine the primary influencing factor of goaf stability, and statistically obtain the simulation results of the orthogonal test scheme; In S2, a numerical model of the orthogonal test scheme for goaf stability analysis is constructed, the rock mechanics parameters of the corresponding scheme are assigned to the corresponding model, and simulation analysis is performed on each scheme.

[0008] S3. Determine the range value of the first influencing factor of goaf stability through the range analysis method, rank the sensitivity of the first influencing factor of goaf stability, eliminate the first influencing factor of goaf stability with a smaller impact, and then obtain the second influencing factor of goaf stability; In S3, through the range analysis method, the larger the range value of the factors affecting the stability of the goaf, the higher the degree of influence, and vice versa; According to the range value, the first influencing factors of goaf stability are ranked as follows: angle between the long axis of the goaf and the direction of maximum principal stress > uniaxial compressive strength > rock quality index RQD value > goaf length > joint surface spacing > goaf height > goaf width > pillar width > goaf burial depth > water inflow > Poisson's ratio; Eliminating the first influencing factors of goaf stability with smaller influence is as follows: comparing the range value of each first influencing factor of goaf stability with the maximum range value, the first influencing factors of goaf stability with a ratio less than 1 / 3 are the first influencing factors of goaf stability with smaller influence, and the first influencing factors of goaf stability with smaller influence are eliminated; In S3, the Poisson's ratio, water inflow, and goaf depth, which are the first influencing factors of goaf stability, are eliminated, and the angle between the long axis of the goaf and the maximum principal stress direction, uniaxial compressive strength, rock quality index RQD value, goaf length, joint surface spacing, goaf height, pillar width, and goaf width are taken as the second influencing factors of goaf stability.

[0009] S4. Construct a goaf stability evaluation model through the analytic hierarchy process, and determine the weight of the second influencing factor of goaf stability based on the second influencing factor of goaf stability determined in S3 and its corresponding extreme value; In S4, the second influencing factors of goaf stability determined are classified to establish the second influencing factor set U 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)}.

[0010] S5. According to the S4 goaf stability evaluation model and the weight of the second influencing factor of goaf stability, determine the fuzzy comprehensive evaluation matrix of goaf stability.

[0011] The mapping function for the conversion of the goaf stability value range is constructed as follows: ; Where, is the measured value of the quantitative indicator; The upper limit of the goaf stability grade evaluation interval corresponding to the measured value of the second influencing factor index of goaf stability; The lower limit of the goaf stability grade evaluation interval corresponding to the measured value of the second influencing factor index of goaf stability; The upper limit of the quantitative range of the goaf stability grade corresponding to the second influencing factor index of goaf stability; It is the lower limit of the quantitative value range of the goaf stability grade corresponding to the second influencing factor index of goaf stability.

[0012] In S5, the membership function constructed for ; ; ; ; Where δ is the neighborhood value centered at the midpoint of the interval within the quantitative value range of the evaluation grade. The membership degrees within the above neighborhood range are calculated through the mapping function and membership function of the goaf stability value range conversion to obtain the membership degrees of the four evaluation grades to which the measured values ​​of the second influencing factor index of goaf stability belong, and the fuzzy comprehensive evaluation matrix R of goaf stability is constructed.

[0013] The fuzzy comprehensive evaluation matrix R of goaf stability is constructed: ; Where, Measured value of quantitative indicator The degree of membership of the evaluation level.

[0014] S6. According to the fuzzy comprehensive evaluation matrix of goaf stability, the evaluation matrix of the second influencing factor of goaf stability is obtained, and then the level of goaf stability is determined.

[0015] The second influencing factors of goaf stability are evaluated in turn, and the evaluation matrix of the second influencing factors of goaf stability is for: ; Calculate the sensitivity ranking and the evaluation matrix of the second influencing factor of goaf stability The maximum eigenvalue of =7.96, and the corresponding eigenvector X is: ; The required eigenvector X is the sensitivity ranking of the second influencing factor of goaf stability. The weight coefficient of the second influencing factor of goaf stability is obtained by normalizing the eigenvector, that is, the weight vector C of the second influencing factor of goaf stability: ; After the weight vector C of the second influencing factor of goaf stability and the fuzzy comprehensive evaluation matrix R are determined, the weight vector C of the second influencing factor of goaf stability is transformed into a fuzzy subset B on the comment set V by performing fuzzy linear transformation on R: ; Where, “◦” is the synthesis operator of the weight vector C of the second influencing factor of goaf stability and the fuzzy comprehensive evaluation matrix R of goaf stability; Since the second influencing factors of goaf stability all have an effect on goaf stability, the weighted average model is adopted. The fuzzy comprehensive evaluation of goaf stability can first obtain the maximum value of the fuzzy subset B vector on the comment set V according to the maximum membership principle. , the value of i ranges from 1 to 4; according to Grading of comprehensive evaluation results; Then, the stability level of the goaf is quantified into scores. Membership is the weight coefficient, and the quantitative score of the goaf stability level is taken The weighted average of the comprehensive evaluation level is taken as the quantitative result FCA, that is: ; According to the quantitative results of the comprehensive evaluation level FCA, the stability level of the goaf can be determined.

[0016] Beneficial effects of the present invention: The present invention provides a comprehensive evaluation method for goaf stability combined with numerical simulation methods. The sensitivity of factors affecting goaf stability is analyzed through orthogonal experiments and numerical simulation methods, and factors with little impact on goaf stability are eliminated. This ensures the rationality and accuracy of goaf stability evaluation and simplifies the stability evaluation process.

[0017] Furthermore, rock mechanics theory and criteria are used in numerical simulation to convert the influencing factors of goaf stability into rock mechanics parameters, thereby realizing the quantitative evaluation of the influencing factors of goaf stability; through numerical simulation and orthogonal analysis, the sensitivity ranking of the influencing factors of goaf stability is obtained, and the influencing factors of goaf stability are assigned weights, thereby avoiding the subjectivity of the goaf stability evaluation left over after mining, and improving the scientific nature of the comprehensive evaluation and the accuracy of the evaluation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure is a flow chart of the comprehensive evaluation method of goaf stability combined with the numerical simulation method of the present invention. DETAILED DESCRIPTION

[0019] 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 accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Instead, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0020] The embodiment of the present invention provides a comprehensive evaluation method for goaf stability combined with numerical simulation method, such as Figure 1 As shown, the specific steps include: S1. Preliminarily determine the first influencing factor of goaf stability and construct a numerical model of the orthogonal test scheme; There are many factors that affect the stability of goaf, including the uniaxial compressive strength of rock, rock quality index RQD, joint spacing, rock integrity coefficient, Poisson's ratio, number of volume joints, structural surface attitude, 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 goafs.

[0021] In this embodiment, the primary influencing factors for goaf stability are determined to include: 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 major axis and the direction of maximum principal stress. These 11 factors are used as the primary influencing factors for goaf stability. An L27 (3^13) orthogonal table is used. The orthogonal table contains 27 trials, with each primary influencing factor for goaf stability set at three levels. This results in 13 primary influencing factors for goaf stability, including two blank factors.

[0022] Specifically, the orthogonal scheme for numerical simulation of goaf stability is shown in Table 1 below: Table 1 Orthogonal schemes for numerical simulation of goaf stability

[0023] Hoek-Brown rock failure criterion expression: (1) Where, is the maximum principal stress at rock mass failure, unit: MPa; is the minimum principal stress at rock mass failure, unit: MPa; is the uniaxial compressive strength of rock, unit is MPa; m is the dimensionless coefficient of the hardness of rock mass; s is the dimensionless coefficient of the degree of rock mass crushing; The dimensionless coefficient m of rock hardness is calculated using the following formula: (2) The dimensionless coefficient s of rock mass fragmentation degree is calculated using the following formula: (3) Where, is the Hoek-Brown constant of the rock mass; The calculation belongs to the existing technology. Specifically, it is based on the comprehensive evaluation of rock mass classification indicators such as rock strength, rock quality index RQD value, joint spacing and groundwater influence, and then calculated through the rock mechanics classification table of jointed rock mass and combined with the values ​​taken in Table 3.

[0024] when = 0, the tensile strength of the rock mass is obtained from the Hoek-Brown rock failure criterion expression : (4) Where, is the tensile strength of the rock mass, in MPa; is the uniaxial compressive strength of rock, unit is MPa; m is the dimensionless coefficient of the hardness of rock mass; s is the dimensionless coefficient of the degree of rock mass crushing; The Hoek-Brown rock failure criterion gives the rock elastic modulus Relationship with RMR: (5) Where, is the elastic modulus of rock mass, unit is GPa; is the uniaxial compressive strength of rock, unit: MPa; The Mohr-Coulomb rock failure criterion states that the maximum principal stress at rock failure and minimum principal stress at rock failure There is a linear relationship between: (6) Where, It is the maximum principal stress when the rock mass fails, in MPa; is the compressive strength of rock mass, unit: MPa; is the minimum principal stress when the rock mass fails, in MPa; k is the linear slope, .

[0025] When 0< <0.25 hour, and Satisfy the Hoek-Brown rock failure criterion expression, and regress Equation (6) to obtain the rock compressive strength and k.

[0026] In addition, the internal friction angle of the rock mass Calculated by the following formula: (7) Where, is the internal friction angle of the rock mass, unit is °; k is the linear slope, ; cohesion of rock mass It can be calculated by the following formula: (8) Where, is the cohesion of the rock mass, unit: MPa; is the rock mass compressive strength, unit is MPa; k is the linear slope, ; Assuming that the surrounding rock of the goaf is limestone, the joint surface is slightly rough, the width is less than 1 mm, and the rock on the joint surface is weak, the corresponding RMR related parameters are obtained by looking up Table 2 based on the rock mass quality data of the orthogonal test scheme for numerical simulation of goaf stability 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.

[0027] Table 2 Numerical simulation calculation parameters of goaf stability

[0028] S2. A numerical model for the orthogonal test of numerical simulation of goaf stability was constructed using flac3d software. The rock mechanics parameters in the orthogonal test of numerical simulation of goaf stability in Table 1 were assigned to the corresponding model. Based on the existing Matthews stability diagram, the stability of the goaf walls is higher than that of the roof. Therefore, the vertical displacement of the roof was used as the statistical analysis indicator to perform an orthogonal analysis of the numerical simulation of goaf stability in Table 1. The statistical vertical displacement of the goaf roof is shown in Table 3.

[0029] Table 3 Roof displacement statistics of numerical simulation scheme for goaf stability

[0030] 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 goaf stability of the roof displacement is calculated, as shown in Table 4.

[0031] Table 4. The range of the first influencing factor of goaf stability in terms of roof displacement

[0032] Through the range analysis method, if the range value of the rock mechanical parameter is large, it means that the influence degree of the rock mechanical parameter is high, otherwise, it means that the influence degree of the rock mechanical parameter is small.

[0033] According to the extreme difference value, the first influencing factors of goaf stability 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 surface spacing > goaf height > goaf width > pillar width > goaf burial depth > water inflow > Poisson's ratio.

[0034] The factors with a ratio of less than 1 / 3 of the extreme value of each influencing factor in the first influencing factor and the maximum extreme value in the first influencing factor are considered to have a small influence and are eliminated. According to the above-mentioned method for eliminating influencing factors, the three factors of Poisson's ratio, water inflow, and goaf depth are eliminated from the first influencing factor 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 surface spacing, goaf height, pillar width, and goaf width are selected as the second influencing factors of goaf stability.

[0035] S4. Construct a goaf stability evaluation model through the analytic hierarchy process, and determine the weight of the second influencing factor of goaf stability based on the second influencing factor of goaf stability determined in S3 and its corresponding extreme value; The second influencing factors of goaf stability are classified and the second influencing factor set U of goaf stability is established, where 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 plane spacing), u6 (goaf height), u7 (goaf width), u8 (pillar width)}; The second factor affecting the stability of the goaf is divided into four stability levels based on the stability classification of engineering rock mass, namely V={V1(stability ), V2 (basically stable ), V3 (less stable ), V4 (unstable )}.

[0036] Among them, V1 (stable ) indicates that no control measures or monitoring are required in the goaf; V2 (basically stable ) indicates that the goaf area needs to be managed and monitored to ensure safe production within its affected area; V3 (less stable ) indicates that measures need to be taken and monitored in the goaf, and emergency plans need to be formulated; V4 (unstable ) indicates that immediate measures must be taken and monitoring must be strengthened in the goaf area, and personnel and equipment within the affected area must be evacuated immediately.

[0037] The evaluation level of the second influencing factor of goaf stability is shown in Table 5 below.

[0038] Table 5 Stability grade of the second influencing factor of goaf stability

[0039] When determining the membership of the four evaluation levels of the second influencing factor of goaf stability, it is first necessary to convert the measured values ​​of the quantitative indicators into numerical values ​​within the quantitative value range, which facilitates the unified construction of the membership function and ultimately makes a comprehensive evaluation of the goaf stability.

[0040] S5. Determine the comprehensive evaluation matrix for goaf treatment based on the goaf stability evaluation model in S4 and the weights of rock mechanics parameters.

[0041] Based on the results of S4, the mapping function for the conversion of the stability range of the goaf is constructed as follows: (9) (10) Where, is the measured value of the quantitative indicator; The upper limit of the goaf stability grade evaluation interval corresponding to the measured value of the second influencing factor index of goaf stability; The lower limit of the goaf stability grade evaluation interval corresponding to the measured value of the second influencing factor index of goaf stability; The upper limit of the quantitative range of the goaf stability grade corresponding to the second influencing factor index of goaf stability; It is the lower limit of the quantitative value range of the goaf stability grade corresponding to the second influencing factor index of goaf stability; Formula (9) in the mapping function for goaf stability range conversion is: The larger the value is, the more stable the goaf is. Formula (10) is The larger it is, the more unstable the goaf is.

[0042] Constructed membership function for (11) (12) (13) (14) Where δ is the neighborhood value centered at the midpoint of the interval within the quantitative value range of the evaluation grade, and the membership degree within the neighborhood is 1.

[0043] 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.

[0044] (15) Where, It is the second influencing factor index of goaf stability Affiliation with evaluation ratings.

[0045] S6. Based on the fuzzy comprehensive evaluation matrix of goaf stability, the evaluation matrix of factors affecting goaf stability is obtained, and then the level of goaf stability is determined.

[0046] After constructing the fuzzy comprehensive evaluation matrix R for goaf stability, it is necessary to determine the weights of factors u1 to u8. In the goaf stability evaluation, factors u1 to u8 have different degrees of influence on goaf stability, so it is necessary to determine the weights of factor indicators u1 to u8.

[0047] In this embodiment, the evaluation target of the fuzzy comprehensive evaluation matrix of goaf stability is the stability of the goaf. Therefore, the evaluation target is determined as the second influencing factor of goaf stability, that is, 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)}. The comprehensive evaluation method for goaf stability in this embodiment is not assigned by human factors, but is determined by the ratio of the extreme value between the two influencing factors of goaf stability, such as the extreme value of the first influencing factor of goaf stability of roof displacement shown in Table 4. This setting effectively avoids the subjectivity of human factor assignment in the process of assigning the influencing factors of goaf stability.

[0048] For example, if u1 (the angle between the long axis of the goaf and the direction of the maximum principal stress) is compared with u2 (uniaxial compressive strength), and the ratio is 1.2, then the angle between the long axis of the goaf and the direction of the maximum principal stress is more important. Then the fuzzy comprehensive evaluation matrix of the goaf stability is: (16)

[0049] Calculate the evaluation matrix of the second influencing factor of goaf stability The maximum eigenvalue λ max =7.96, and the corresponding eigenvector X is: (17) The required eigenvector X is the sensitivity ranking of the second influencing factor of goaf stability. The weight coefficient of the second influencing factor of goaf stability is obtained by normalizing the eigenvector, that is, the weight vector C of the second influencing factor of goaf stability: (18) After the weight vector C of the second influencing factor of goaf stability and the fuzzy comprehensive evaluation matrix R of goaf stability are determined, the fuzzy linear transformation of the fuzzy comprehensive evaluation matrix R of goaf stability is performed to transform the weight vector C of the second influencing factor of goaf stability into a fuzzy subset B on the comment set V: (19) Where, It is the synthetic operator of the weight vector C of the second influencing factor of goaf stability and the fuzzy comprehensive evaluation matrix R of goaf stability. Since the second influencing factors of goaf stability all have an effect on the stability of the goaf, the weighted average model is adopted.

[0050] Then, the stability level of the goaf is quantified into scores. Membership is the weight coefficient, take each Vai The weighted average of the comprehensive evaluation level is taken as the quantitative result FCA, that is: (20) According to the quantitative result FCA of the comprehensive evaluation level, the stability level of the goaf under the evaluation condition is obtained.

[0051] Example calculation: The factor set U of the second influencing factor of the stability of the goaf of a certain mine is U={10, 40, 60, 30, 85, 25, 8, 22}; The mapping value f(u i )={0.833, 0.4, 0.6, 0.6667, 0.6750, 0.3750, 0.5, 0.7750}; Then, according to equations (11) to (14), the membership function A j (f(u i )), the fuzzy comprehensive evaluation matrix R of the mine goaf stability is calculated as ; By making a fuzzy linear change in R, that is, by using equations (16)-(18), the weight vector C of the second influencing factor of goaf stability is transformed into a fuzzy subset B (19) on the comment set V. Substituting the above fuzzy comprehensive evaluation matrix R of the goaf stability of the mine into equation (19), we can get B=[0.24667,0.45833,0.295,0]; substituting the B value into the quantitative result FCA of the comprehensive evaluation grade of equation (20), we get FCA=0.61292; According to the above B value and FCA value, it can be determined that the goaf of the mine is II basically stable.

[0052] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may alter, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A comprehensive evaluation method for goaf stability combined with numerical simulation method, characterized in that: include: S1. Preliminarily determine the first influencing factor of goaf stability, construct an orthogonal test scheme for goaf stability analysis, and build a numerical model for the orthogonal test scheme; S2. Assign rock mechanics parameters to the numerical model of the orthogonal test scheme, perform numerical simulation analysis, determine the primary influencing factor of goaf stability, and statistically obtain the simulation results of the orthogonal test scheme; S3. Determine the range value of the first influencing factor of goaf stability by using the range analysis method, rank the sensitivity of the first influencing factor of goaf stability, eliminate the first influencing factor of goaf stability with a smaller impact, and then obtain the second influencing factor of goaf stability; S4. Construct a goaf stability evaluation model through the analytic hierarchy process, and determine the weight of the second influencing factor of goaf stability based on the second influencing factor of goaf stability determined in S3 and its corresponding extreme value; S5. Determine the fuzzy comprehensive evaluation matrix of goaf stability based on the goaf stability evaluation model in S4 and the weight of the second influencing factor of goaf stability; S6. According to the fuzzy comprehensive evaluation matrix of goaf stability, the evaluation matrix of the second influencing factor of goaf stability is obtained, and then the level of goaf stability is determined.

2. The method for comprehensive evaluation of goaf stability combined with numerical simulation method according to claim 1, characterized in that: In S1, the first influencing factors of the goaf stability 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 goaf length, the joint surface spacing, the goaf height, the goaf width, the pillar width, the goaf burial depth, the water inflow, and the Poisson's ratio.

3. The comprehensive evaluation method for goaf stability combined with numerical simulation method according to claim 1, characterized in that: In the S2, a numerical model of the orthogonal experimental scheme for goaf stability analysis is constructed, rock mechanics parameters are assigned to the numerical model of the orthogonal experimental scheme for goaf stability analysis, and a simulation analysis of the orthogonal experimental scheme for goaf stability analysis is performed.

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

5. The comprehensive evaluation method for goaf stability combined with numerical simulation method according to claim 4, characterized in that: In said S3: The method of eliminating the first influencing factors of goaf stability with smaller influence is as follows: comparing the extreme difference value of each first influencing factor of goaf stability with the maximum extreme difference value, the first influencing factors of goaf stability with a ratio less than 1 / 3 are considered as the first influencing factors of goaf stability with smaller influence, and the first influencing factors of goaf stability with smaller influence are eliminated; In S3, the Poisson's ratio, water inflow, and goaf depth, which are the first influencing factors of goaf stability, are eliminated, and the angle between the long axis of the goaf and the maximum principal stress direction, uniaxial compressive strength, rock quality index RQD value, goaf length, joint surface 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 combined with numerical simulation method according to claim 5, characterized in that: In said S4, the selected second influencing factors of goaf stability are classified, and a set U of second influencing factors of goaf stability is established, where 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)}.

7. The comprehensive evaluation method for goaf stability combined with numerical simulation method according to claim 6, characterized in that: The mapping function for the conversion of the stability range of the goaf area is constructed as follows: ； Where, is the measured value of the quantitative indicator; The upper limit of the goaf stability grade evaluation interval corresponding to the measured value of the second influencing factor index of goaf stability; The lower limit of the goaf stability grade evaluation interval corresponding to the measured value of the second influencing factor index of goaf stability; The upper limit of the quantitative range of the goaf stability grade corresponding to the second influencing factor index of goaf stability; It is the lower limit of the quantitative value range of the goaf stability grade corresponding to the second influencing factor index of goaf stability.

8. The comprehensive evaluation method for goaf stability combined with numerical simulation method according to claim 7, characterized in that: In said S5, the membership function constructed for: ； ； ； ； Where δ is the neighborhood value centered at the midpoint of the interval within the quantitative value range of the evaluation grade. The membership degrees within the neighborhood range are calculated through the mapping function and membership function of the goaf stability value range conversion to obtain the membership degrees of the four evaluation grades to which the measured values ​​of the second influencing factor index of goaf stability belong, and the fuzzy comprehensive evaluation matrix R of goaf stability is constructed.

9. The comprehensive evaluation method for goaf stability combined with numerical simulation method according to claim 8, characterized in that: The fuzzy comprehensive evaluation matrix R of goaf stability: ； Where, Indicates evaluation indicators Affiliation with evaluation ratings.

10. The comprehensive evaluation method for goaf stability combined with numerical simulation method according to claim 9, characterized in that: In the step S6, the evaluation matrix of the second influencing factor of goaf stability is constructed. Then, the evaluation matrix of the second influencing factor of goaf stability is for: ； According to the sensitivity ranking, the evaluation matrix P of the second influencing factor of goaf stability is calculated. T The maximum eigenvalue of =7.96, and the corresponding eigenvector X is: ； The obtained eigenvector X is the sensitivity ranking of the second influencing factor of goaf stability. The weight coefficient of the second influencing factor of goaf stability is obtained by normalizing the eigenvector X, that is, the weight vector C of the second influencing factor of goaf stability: ； After the weight vector C of the second influencing factor of goaf stability and the fuzzy comprehensive evaluation matrix R of goaf stability are determined, the weight vector C of the second influencing factor of goaf stability is converted into a fuzzy subset B on the comment set V through the fuzzy comprehensive evaluation matrix R of goaf stability. The specific conversion process is as follows: ； Where, B is the fuzzy subset of the comment set V; C is the weight vector of the second influencing factor of goaf stability; R is the fuzzy comprehensive evaluation matrix of goaf stability; It is the synthesis operator of the weight vector C of the second influencing factor of goaf stability and the fuzzy comprehensive evaluation matrix R of goaf stability; The fuzzy comprehensive evaluation of goaf stability can first be based on the maximum membership principle to obtain the maximum value of the fuzzy subset B vector on the evaluation set V. , i ranges from 1 to 4; according to The results of the above tests determine the stability level of the goaf; Quantitative score based on goaf stability level Membership is the weight coefficient, and the quantitative score of each goaf stability level is taken The weighted average value of is taken as the quantitative result FCA of the goaf stability level, namely: ； According to the quantitative results FCA of goaf stability level, the goaf stability level is obtained.

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