Method for determining weight of influence factor of pressure relief effect of protective layer based on finite element analysis

Abstract

The invention discloses a method for determining weights of influence factors of a pressure relief effect of a protective layer based on finite element analysis, which comprises the following steps of: selecting and determining a vertical stress change rate as an evaluation index of the pressure relief effect of the protective layer, and selecting the influence factors influencing the pressure relief effect of the protective layer; constructing a three-dimensional finite element numerical analysis model and designing orthogonal experiment schemes of different influence factors; obtaining pressure relief effect evaluation index values corresponding to different experiment schemes, and obtaining range, F value and P value data of the pressure relief effect evaluation index values under the change of different influence factors; and finally, analyzing the significance of each influence factor according to the data, and determining the weight value of each influence factor. The method is high in applicability, wide in applicability and simple in principle, the influence of multi-factor coupling on the pressure relief effect of the protection layer can be explored, the factor weight influencing the pressure relief effect is obtained, and therefore data support is provided for follow-up actual protection layer pressure relief construction parameters.

Description

Technical Field

[0001] The invention relates to the field of coal mining and coal mine safety, and in particular to a method for determining weights of factors affecting the pressure relief effect of a protective layer based on finite element analysis. Background Art

[0002] There are many factors that affect the decompression effect of the underlying coal and rock layers after the protective layer is mined: including the thickness of the protective layer, the spacing between coal seams, lithology, and burial depth. In order to determine the influence of each influencing factor on the decompression effect, the influence of different influencing factors is currently mainly obtained through experiments. However, due to the large number of influencing factors, the influence of a single influencing factor requires adjusting multiple data for separate experiments. If a multi-factor coupling experiment is conducted, there will be too many test plans, and the experiment will be difficult to implement. It is difficult to analyze the impact of multi-factor coupling on the overall decompression effect, and it is impossible to accurately obtain the weights of the different influencing factors on the decompression effect under the multi-factor coupling condition. Since the weights of each influencing factor cannot be determined, it is impossible to provide data support for the actual protective layer decompression construction parameters. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for determining the weights of factors affecting the pressure relief effect of the protective layer based on finite element analysis. Based on mathematical statistics and the principle of orthogonal experiment, a variety of orthogonal experimental conditions are designed. The orthogonal experimental conditions are simulated by using FLAC numerical software to explore the influence of multi-factor coupling on the pressure relief effect of the protective layer. The weights of the factors affecting the pressure relief effect are obtained, thereby providing data support for the subsequent actual protective layer pressure relief construction parameters.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is: a method for determining the weights of factors affecting the pressure relief effect of the protective layer based on finite element analysis, the specific steps are:

[0005] Step 1: Determine the vertical stress change rate as an evaluation index for the pressure relief effect of the protective layer.

[0006] Step 2: Collect the mine geological data, analyze the geological data, and select the factors that affect the pressure relief effect of the protective layer.

[0007] Step 3: Construct a three-dimensional finite element numerical analysis model based on the geological data collected in step 2, and design orthogonal experimental schemes for different influencing factors based on the influencing factors selected in step 2.

[0008] Step 4: Substitute the orthogonal experimental schemes of different influencing factors into the three-dimensional finite element numerical analysis model for calculation, and obtain the pressure relief effect evaluation index values ​​corresponding to different experimental schemes.

[0009] Step 5: Calculate the range, F value and P value data of the pressure relief effect evaluation index under different influencing factors.

[0010] Step 6: Analyze the significance of each influencing factor based on the calculation results of step 5 and determine the weight value of each influencing factor.

[0011] Furthermore, the specific formula of the vertical stress change rate in step 1 is:

[0012]

[0013] Where: S i It represents the vertical stress on the coal pillar side of the i-th scheme; S0 is the original rock stress; and when S is greater than 1, it is determined that stress concentration occurs on the coal seam roof under the current scheme; when S is less than 1, it is determined that stress reduction occurs on the coal seam roof under the current scheme; the larger the S value, the lower the degree of pressure relief, and the smaller the value, the higher the degree of pressure relief.

[0014] Furthermore, the step two is specifically as follows: there are many factors that affect the pressure relief effect of protective layer mining in rock burst mines. The geological conditions of the protective layer, mining parameters and the interaction with the upper and lower coal seams are the main factors affecting the pressure relief effect; representative parameters are selected as the values ​​of the level for different factors, and the interaction between the factor levels is not considered. The orthogonal test method is used to determine the number of test schemes that require numerical simulation, so as to obtain effective and comprehensive calculation data while reducing the calculation workload; finally, the thickness of the protective layer, the spacing between coal seams and the interlayer lithology are selected as the influencing factors affecting the pressure relief effect of the protective layer.

[0015] Furthermore, the specific process of constructing the three-dimensional finite element numerical analysis model in the step three is: according to the distribution of coal and rock layers in the boreholes in the mine geological data, a three-dimensional finite element numerical analysis model of the pressure relief effect of the mine protective layer based on FLAC3D is established. The simulation adopts solid unit simulation, and the destruction conforms to the Mohr Coulomb strength criterion; the model studies the influence of no tectonic stress in the area, and sets the entire study area to be in a uniformly distributed stress field, ignoring the influence of water, and adopts a displacement boundary in the x direction of the model to limit the displacement in the x direction; adopts a displacement boundary in the y direction to limit the displacement in the y direction; adopts a displacement boundary at the bottom boundary of the model to limit the displacement in the z direction, and adopts a free boundary at the upper boundary of the model to apply vertical stress.

[0016] Furthermore, the specific process of designing the orthogonal experimental scheme of different influencing factors in step three is as follows: the influencing factors selected in step two are: coal seam spacing, protective layer thickness, and interlayer lithology; when performing variance analysis on the orthogonal experiment, the random error must be estimated, and the random error is obtained through the blank columns in the orthogonal table; since there is no factor effect in the blank column, it can reflect the error caused by the random factor. Set a group of blank columns, do not consider the interaction between the influencing factors, that is, each influencing factor acts independently, and select 4 factors and 4 levels L 16 (4 4 ), that is, four representative parameters are selected for the three influencing factors respectively, with blank columns.

[0017] Furthermore, the step five is specifically: calculating parameters such as the range, F value and P value of different factors.

[0018] ① According to formula (1), the stress change rate S between the vertical stress on the coal pillar side and the original rock stress in scheme i is obtained.

[0019] ②. Obtain the sum of the test results when the level number is i on column m.

[0020]

[0021] Where n is the number of times each level appears in any column, k i K i The average of .

[0022] ③. Obtain the range between the maximum sum and the minimum sum.

[0023] R=max{k1,k2,k3,k4}-min{k1,k2,k3,k4} (4)

[0024] ④、Sum of squares of deviations of each influencing factor S j .

[0025]

[0026] Where n is the number of times each level appears in any column, n0 is the total number of trials, and y i The experimental results of scheme i.

[0027] ⑤. Mean square σ.

[0028]

[0029] Among them, S j It represents the sum of squares of deviations of various influencing factors, L represents the degree of freedom, L=n-1.

[0030] ⑥. F value.

[0031]

[0032] Among them, σ represents the mean square, σ s represents the mean square error.

[0033] ⑦. P value.

[0034] The P value is obtained by consulting an F distribution table or using statistical software based on the calculated F value and the corresponding degrees of freedom; it represents the probability that the obtained F value is more extreme than the observed value when the null hypothesis (that the group means are equal) holds.

[0035] Furthermore, the step six is ​​specifically as follows: obtaining the range, F value and P value data of each of the three influencing factors calculated in step five, which can reflect the significant influence of each influencing factor on the pressure relief effect, and the larger the F value and the smaller the P value of a single influencing factor, the more significant its influence on the pressure relief effect, thereby determining the relative importance of each influencing factor on the pressure relief effect, and finally allocating a weight value to each influencing factor according to the determined relative importance.

[0036] Compared with the prior art, the present invention selects to determine the vertical stress change rate as the evaluation index of the protective layer pressure relief effect, and selects the influencing factors that affect the pressure relief effect of the protective layer according to the mine geological data; then constructs a three-dimensional finite element numerical analysis model and designs orthogonal experimental schemes for different influencing factors; thereby obtaining the pressure relief effect evaluation index values ​​corresponding to different experimental schemes, and obtaining the range, F value and P value data of the pressure relief effect evaluation index value under different changes in influencing factors; finally, according to the significance of each influencing factor analysis data, the weight value of each influencing factor is determined. This method has strong applicability, wide applicability, and simple principle. By analyzing the vertical stress change rate of the protected layer under different pressure relief parameters, the influence of multi-factor coupling on the pressure relief effect of the protective layer is explored, and the weight of the factors affecting the pressure relief effect is obtained, thereby providing data support for the subsequent actual protective layer pressure relief construction parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A numerical simulation model established for the coal and rock strata data of the 22103 working face of a coal mine in the embodiment;

[0038] Figure 2A It is a cloud diagram of vertical stress on the roof of the protected coal seam in a certain scheme of orthogonal test in the embodiment;

[0039] Figure 2B It is a broken line diagram of vertical stress on the roof of the protected coal seam in a certain scheme of orthogonal test in the embodiment;

[0040] Figure 3 This is a weight diagram of the pressure relief effect on the working face in the embodiment. DETAILED DESCRIPTION

[0041] The present invention will be further described below.

[0042] Embodiment: The method of the present invention is used to determine the weights of factors affecting the pressure relief effect of the protective layer on the 22103 working face of a coal mine. The specific steps are as follows:

[0043] Step 1: Determine the vertical stress change rate as the evaluation index of the pressure relief effect of the protective layer. The specific formula of the vertical stress change rate is:

[0044]

[0045] Where: S i It represents the vertical stress on the coal pillar side of the ith scheme; S0 is the original rock stress; and when S is greater than 1, it means that stress concentration occurs in the roof of the 2-2 coal seam; when S is less than 1, it means that stress reduction occurs in the roof of the 2-2 coal seam. The larger the S value, the lower the degree of pressure relief, and the smaller the value, the higher the degree of pressure relief.

[0046] Step 2: Collect the geological data of the mine, analyze the geological data, and select the factors that affect the pressure relief effect of the protective layer. Specifically, there are many factors that affect the pressure relief effect of the protective layer mining in the impact rock pressure mine. The geological conditions, mining parameters and interaction between the protective layer and the upper and lower coal seams are the main factors affecting the pressure relief effect. For different factors, representative parameters are selected as the values ​​of the level without considering the interaction between the factor levels. The orthogonal test method is used to determine the number of test schemes that need numerical simulation, so as to obtain effective and comprehensive calculation data while reducing the calculation workload. Finally, the thickness of the protective layer, the spacing between coal seams and the lithology between layers are selected as the factors affecting the pressure relief effect of the protective layer.

[0047] In this example, the coal mine field is about 7.4 km long from north to south, about 13.0 km wide from east to west, and covers an area of ​​92.76 km 2 The production capacity is 8.0Mt / a. The recoverable reserves of 2-1 coal and 2-2 medium coal are 466 million tons, with a service life of 25.6 years.

[0048] Step 3: construct a three-dimensional finite element numerical analysis model based on the geological data collected in step 2, and design orthogonal experimental schemes for different influencing factors based on the influencing factors selected in step 2. The specific process of constructing the three-dimensional finite element numerical analysis model in this embodiment is as follows: by sorting out the current coal mine on-site geological data, the geological borehole closest to the 22103 working face is the H07 borehole. Therefore, based on the geological conditions of the H07 borehole, a three-dimensional finite element numerical analysis model based on the FLAC3D mine protective layer pressure relief effect is established. The simulation uses solid unit simulation, and the destruction meets the Mohr Coulomb strength criterion; the There is no influence of tectonic stress in the model study area. The study area is set to be in a uniformly distributed stress field. The influence of water is not considered. The simulation range of the model is determined to be length × width × height = 1000 × 1200 × 230m. The displacement boundary is used in the x direction of the model to limit the displacement in the x direction; the displacement boundary is used in the y direction to limit the displacement in the y direction; the displacement boundary is used at the bottom boundary of the model to limit the displacement in the z direction. The upper boundary of the model adopts a free boundary to apply vertical stress. The mass of the upper rock layer of the model is replaced by a uniformly distributed load. According to the mining depth of the working face, the average density of the actual rock mass is known to be 2500kg / m 3 , the vertical stress applied is calculated to be 16.25MPa, such as Figure 1 shown.

[0049] Design of orthogonal experimental scheme with different influencing factors The specific process of this embodiment is as follows: Step 2 The influencing factors selected are: coal seam spacing, protective layer thickness, and interlayer lithology, a total of 3; When performing variance analysis on the orthogonal experiment, random errors must be estimated, and the random errors are obtained through blank columns on the orthogonal table; Since there are no factors in the blank columns, the errors caused by random factors can be reflected. A group of blank columns is set, and the interaction between the influencing factors is not considered, that is, each influencing factor acts independently, and 4 factors and 4 levels L are selected 16 (4 4 ), that is, four representative parameters are selected for the three influencing factors, with blank columns as shown in Table 1. Except for the coal seam spacing, protective layer thickness, and interlayer lithology, which all obey the orthogonal experimental design, the other parameters are kept consistent, and the orthogonal experimental design table of each influencing factor can be obtained. Taking the coal seam spacing as an example, as shown in Table 2, the other two influencing factors are similar to Table 2.

[0050] Table 1 Orthogonal test factor level table

[0051]

[0052] Table 2 Orthogonal test design table

[0053]

[0054]

[0055] Step 4: Substitute the orthogonal experimental schemes of different influencing factors into the three-dimensional finite element numerical analysis model for calculation, and obtain the pressure relief effect evaluation index values ​​corresponding to the different experimental schemes. In this embodiment, the specific values ​​are:

[0056] The following calculation process is carried out for each orthogonal experimental scheme determined in step three. The specific calculation process is as follows: initialize the three-dimensional finite element numerical analysis model → initialize the stress field → original rock stress balance → mining working face → stress field balance → tunnel excavation of protected coal seam → stress field balance → end of simulation.

[0057] ① A total of 16 numerical simulation schemes are used to evaluate the pressure relief effect of the coal seam below after the protective layer is mined by analyzing and comparing the response change law of the stress of the protected layer below after the protective layer is mined.

[0058] ② Numerical calculation model under the coal seam spacing, coal thickness and lithology conditions of the protective layer 2-1 coal seam and the 2-2 coal seam. Two 320m long working faces are set at 165m along the X-axis direction to mine the coal seam. The strike length of the working face is 1200m and the width of the coal pillar is 30m. After the calculation and balance of each tunnel excavation model, the model is vertically sliced ​​at 600m in the Y-axis direction, and the vertical stress distribution of the roof of the protected layer 2-2 coal seam of the model is analyzed to determine its vertical stress change rate. The vertical stress of the dip section and the vertical stress of the roof of the protected layer 2-2 coal seam are as follows: Figure 2A and 2B As shown in Table 3, the pressure relief effect evaluation index values ​​corresponding to different test schemes are shown in Table 3.

[0059] Table 3 Pressure relief effect analysis table

[0060]

[0061]

[0062] Note: The numbers in the blank columns are the horizontal numbers for error analysis.

[0063] Step 5: Calculate the range, F value and P value data of the pressure relief effect evaluation index value under different influencing factors. In this embodiment, the specific data are as follows:

[0064] The test results of coal seam spacing, protective layer thickness and lithology are divided into three groups, represented by K1, K2 and K3. 11 =y1+y2+y3+y4, which represents the sum of the test results when the coal seam spacing is selected as 10m; K 12 =y1+y5+y9+y 13 Represents the sum of the test results when the protective layer thickness is 1m; K13 =y1+y6+y 11 +y 16 It represents the sum of the test results when the interlayer lithology is sandy mudstone. K1, K2, K3 are the average values ​​of k1, k2, k3 respectively. By analyzing the vertical stress of the protected layer under different pressure relief parameters, the influence of various factors on the pressure relief effect of the protected layer is determined, so as to comprehensively evaluate the pressure relief effect of the protective layer of the 2-2 coal seam.

[0065] The vertical stress change rate S under 16 simulation schemes is shown in Table 4.

[0066] Table 4 Vertical stress change rate R range table

[0067]

[0068] Table 5 Variance analysis table

[0069]

[0070] Step 6: Analyze the significance of each influencing factor according to the calculation results of step 5, and determine the weight value of each influencing factor. Specifically, obtain the range, F value and P value data of the three influencing factors calculated in step 5. The data can reflect the significant influence of each influencing factor on the pressure relief effect, and determine the relative importance of each influencing factor on the pressure relief effect. The larger the F value and the smaller the P value of a single influencing factor, the more significant its influence on the pressure relief effect, and the higher its weight ratio. Specifically:

[0071] Variance analysis is one of the basic methods of mathematical statistics. It is widely used in industrial and agricultural production and scientific research test data analysis. Variance analysis (ANOVA), also known as "variance analysis", was invented by RA Fisher and is used for significance tests of the mean differences of two or more samples. Variance analysis includes steps such as proposing hypotheses, determining test statistics, and decision analysis.

[0072] As shown in Table 4, by comparing the extreme values ​​of vertical stress S at different levels, it can be found that the order of the influence of various factors on S (vertical stress change rate) is coal seam spacing, protective layer thickness, and lithology, among which coal seam spacing is an important factor, protective layer thickness is a secondary factor, and lithology is a general factor. The weights of coal seam spacing, protective layer thickness and lithology affecting the unloading effect of protective layer are 0.66 / (0.66+0.26+0.17)=0.60, 0.26 / (0.66+0.26+0.17)=0.24 and 0.17 / (0.66+0.26+0.17)=0.16 respectively, among which 0.66, 0.26 and 0.17 are the corresponding extreme values ​​of coal seam spacing, protective layer thickness and lithology respectively; since the current study only considers coal seam spacing and protective layer thickness, the weight of protective layer thickness becomes 0.26 / (0.26+0.66)=0.28, and the weight of coal seam spacing becomes 0.66 / (0.26+0.66)=0.72.

[0073] The mining simulation results of the working face of the 16 orthogonal test schemes designed above were analyzed, and the vertical stress change rate parameter was selected to evaluate the pressure relief effect of the protective layer. The weight of the protective layer thickness and the coal seam spacing was analyzed based on the extreme difference of vertical stress. The protective layer thickness and coal seam spacing were normalized to obtain the protective layer pressure relief effect evaluation index based on the vertical stress change rate in different areas of the protected layer in the mining area.

[0074] Assume that the distance between coal seams at any position i in the protected layer is d i , the thickness of the protective layer is h i , then the normalized coal seam spacing is d i(nom) and the protective layer thickness is h i(nom) They are:

[0075]

[0076] where d min ,d max is the minimum and maximum value of the coal seam spacing in the mining area, h min 、h max It is the minimum and maximum value of coal seam thickness in the mining area.

[0077] According to the law of pressure relief of protective layer, when the thickness of protective layer is larger, the pressure relief effect of protected layer is better, so the thickness of protective layer is positively correlated with the pressure relief effect of protective layer; when the distance between coal seams is larger, the pressure relief effect of protected layer is worse, so the thickness of protective layer is negatively correlated with the pressure relief effect of protective layer. Then the pressure relief effect evaluation index PR is established (stress) as follows:

[0078] PR (stress) =0.72d i(nom) -0.28hi(nom)

[0079] Finally, the vertical stress PR of the protective layer is obtained. (stress) The pressure relief effect evaluation index distribution is as follows: Figure 3 As shown in the figure, the pressure relief effect of the 22103 working face is better in the early stage of mining, and its pressure relief effect evaluation index PR (stress) The pressure relief degree is about 0.6. As the mining progresses, the pressure relief degree continues to increase, and the maximum pressure relief effect is about 0.6 when the mining reaches about 1500m. In the subsequent working face mining process, the pressure relief effect of the protective layer gradually decreases, and the lowest value is about 0.5.

[0080] According to the principle of multi-factor variance test, the orthogonal test results were tested for inter-subject effects using SPSS (Statistical Product and Service Solutions) software, and the significance levels of protective layer thickness, coal seam spacing and lithology were obtained. The test results are shown in Table 5. The larger the F value, the greater the difference between the corresponding factor and other factors between groups. The differences between coal seam spacing, coal seam thickness and lithology are significant. The significance level P values ​​of factors such as coal seam spacing, protective layer thickness and lithology are all less than 0.2. That is, the influence of coal seam spacing, protective layer thickness and lithology on the pressure relief effect is significant. Finally, it is concluded that the influence of coal seam spacing on the pressure relief effect is the most significant, the influence of protective layer thickness on the pressure relief effect is significant, and the lithology has a certain influence on the pressure relief effect. The weight values ​​of the three are allocated according to the determined relative importance.

[0081] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining the weights of factors affecting the pressure relief effect of a protective layer based on finite element analysis, characterized in that: The specific steps are: Step 1: Determine the vertical stress change rate as an evaluation index for the pressure relief effect of the protective layer; Step 2: Collect the geological data of the mine, analyze the geological data, and select the factors that affect the pressure relief effect of the protective layer; Step 3: construct a three-dimensional finite element numerical analysis model based on the geological data collected in step 2, and design orthogonal experimental schemes for different influencing factors based on the influencing factors selected in step 2; Step 4: Substituting the orthogonal experimental schemes of different influencing factors into the three-dimensional finite element numerical analysis model for calculation, the pressure relief effect evaluation index values ​​corresponding to the different experimental schemes are obtained; Step 5, calculating the range, F value and P value data of the pressure relief effect evaluation index value under different influencing factors; Step 6: Analyze the significance of each influencing factor based on the calculation results of step 5 and determine the weight value of each influencing factor.

2. The method for determining the weights of factors affecting the pressure relief effect of the protective layer based on finite element analysis according to claim 1 is characterized in that: The specific formula of the vertical stress change rate in step 1 is: Where: S i It represents the vertical stress on the coal pillar side of the i-th scheme; S0 is the original rock stress; and when S is greater than 1, it is determined that the stress concentration occurs on the coal seam roof under the current scheme; when S is less than 1, it is determined that the stress reduction occurs on the coal seam roof under the current scheme; The larger the S value, the lower the pressure relief degree, and the smaller the value, the higher the pressure relief degree.

3. The method for determining the weights of factors affecting the pressure relief effect of the protective layer based on finite element analysis according to claim 1 is characterized in that: The specific steps of step 2 are as follows: there are many factors that affect the pressure relief effect of protective layer mining in rock burst mines. The geological conditions of the protective layer, mining parameters and the interaction with the upper and lower coal seams are the main factors affecting the pressure relief effect; representative parameters of different factors are selected as the values ​​of this level, without considering the interaction between the factor levels, and finally the protective layer thickness, coal seam spacing and interlayer lithology are selected as the influencing factors affecting the pressure relief effect of the protective layer.

4. The method for determining the weights of factors affecting the pressure relief effect of the protective layer based on finite element analysis according to claim 1 is characterized in that: The specific process of constructing the three-dimensional finite element numerical analysis model in the step three is: according to the distribution of coal and rock layers in the boreholes in the mine geological data, a three-dimensional finite element numerical analysis model based on the FLAC3D mine protective layer pressure relief effect is established. The simulation adopts solid unit simulation, and the destruction conforms to the Mohr Coulomb strength criterion; the model studies the influence of no tectonic stress in the area, and sets the entire study area to be in a uniformly distributed stress field, ignoring the influence of water, and adopts a displacement boundary in the x direction of the model to limit the displacement in the x direction; adopts a displacement boundary in the y direction to limit the displacement in the y direction; adopts a displacement boundary at the bottom boundary of the model to limit the displacement in the z direction, and adopts a free boundary at the upper boundary of the model to apply vertical stress.

5. The method for determining the weights of factors affecting the pressure relief effect of the protective layer based on finite element analysis according to claim 1 is characterized in that: The specific process of designing the orthogonal experimental scheme with different influencing factors in step 3 is as follows: the influencing factors selected in step 2 are: coal seam spacing, protective layer thickness, and interlayer lithology; when performing variance analysis on the orthogonal experiment, the random error must be estimated, and the random error is obtained by the blank column on the orthogonal table; the interaction between the influencing factors is not considered, and 4 factors and 4 levels L are selected 16 (4 4 ), that is, four representative parameters are selected for the three influencing factors respectively, with blank columns.

6. The method for determining the weights of factors affecting the pressure relief effect of the protective layer based on finite element analysis according to claim 2 is characterized in that: The step five is specifically: calculating parameters such as the range, F value and P value of different factors. ① According to formula (1), the stress change rate S between the vertical stress on the coal pillar side and the original rock stress in scheme i is obtained: ②. Obtain the sum of the test results when the level number is i on the m column: Where n is the number of times each level appears in any column, k i K i The average of ③. Obtain the range between the maximum sum and the minimum sum: R=max{k1,k2,k3,k4}-min{k1,k2,k3,k4} (4) ④、Sum of squares of deviations of each influencing factor S j : Where n is the number of times each level appears in any column, n0 is the total number of trials, and y i is the test result of scheme i; ⑤, Mean square σ: Among them, S j It represents the sum of squares of deviations of each influencing factor, L represents the degree of freedom, L = n-1; ⑥F value: Among them, σ represents the mean square, σ s represents the mean square error; 7. P value: The P value is obtained by consulting an F distribution table or using statistical software based on the calculated F value and the corresponding degrees of freedom; it represents the probability that the obtained F value is more extreme than the observed value when the null hypothesis is true.

7. The method for determining weights of factors affecting the pressure relief effect of protective layer based on finite element analysis according to claim 1, characterized in that: The step six is ​​specifically as follows: obtaining the range, F value and P value data of the three influencing factors calculated in step five, which can reflect the significant influence of each influencing factor on the pressure relief effect, and the larger the F value and the smaller the P value of a single influencing factor, the more significant its influence on the pressure relief effect, thereby determining the relative importance of each influencing factor on the pressure relief effect, and finally allocating a weight value to each influencing factor according to the determined relative importance.

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