A method for evaluating roof blasting decompression effect based on analytic hierarchy process

Abstract

The present invention discloses a roof blasting pressure relief effect evaluation method based on the hierarchical analysis method, including: determining the influencing factors that affect the quality of the coal mine roof blasting pressure relief effect; determining the importance index of each influencing factor, and determining the weight of each influencing factor based on the hierarchical analysis method; determining the pressure relief effect interval index of each influencing factor according to the change of relevant statistical indicators of each influencing factor within a given time before and after the blasting; weighted summing the weight of each influencing factor and the pressure relief effect interval index to obtain an evaluation result; and grading the coal mine roof blasting pressure relief effect according to the evaluation result. The present invention can test and accurately evaluate the effect after implementing the roof blasting pressure relief measures, reduce the possibility of impact danger events, and achieve accurate prediction of dynamic disasters.

Description

Technical Field

[0001] The invention relates to the technical field of safe production of coal mines, and more particularly to a method for evaluating the effect of roof blasting pressure relief based on a hierarchical analysis method. Background Art

[0002] In recent years, the mining depth of coal mines in my country has reached thousands of meters. With the increase in mining depth, the geological conditions of deep mines have become more complex. The superposition of multiple factors such as fault structure, fold structure, high ground stress, and hard roof has had a serious impact on the production and safety of coal mines. Moreover, due to the frequent occurrence of rock burst accidents in coal mines induced by mining, the research and development of related technologies for rock burst prevention and control under complex geological conditions cannot be ignored. At the same time, under the mining conditions of hard roof, it is difficult to effectively test and accurately evaluate the effect of using advanced working face roof blasting measures to relieve pressure in areas with impact hazards. At present, the roof blasting relief measures used in most coal mines are inefficient and cannot accurately and quantitatively grasp the relief effect. This may lead to unnecessary secondary relief or insufficient relief, threatening the safety of coal mine production.

[0003] Therefore, how to test and accurately evaluate the effects of roof blasting and pressure relief measures during the working face mining process, reduce the possibility of impact hazards, and accurately predict dynamic disasters is an urgent problem that technical personnel need to solve. Summary of the invention

[0004] In view of this, the present invention provides a method for evaluating the effect of roof blasting pressure relief based on the hierarchical analysis method, which can test and accurately evaluate the effects of roof blasting pressure relief measures after implementation, reduce the possibility of impact danger events, and achieve accurate prediction of dynamic disasters.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for evaluating roof blasting pressure relief effect based on hierarchical analysis method, characterized by comprising:

[0007] Determine the factors that affect the effect of coal mine roof blasting pressure relief;

[0008] Determine the importance index of each of the influencing factors, and determine the weight of each of the influencing factors based on the hierarchical analysis method;

[0009] Determine the pressure relief effect interval index of each of the influencing factors according to the changes in relevant statistical indicators of each of the influencing factors within a given time before and after the blasting;

[0010] The weights of the influencing factors and the pressure relief effect interval index are weighted and summed to obtain an evaluation result;

[0011] Based on the evaluation results, the decompression effect of coal mine roof blasting is graded.

[0012] Furthermore, the influencing factors include: changes in microseismic energy, changes in hydraulic support resistance, and changes in stress online monitoring;

[0013] The microseismic energy change is: the change of the relevant statistical value of the microseismic energy monitored by the microseismic monitoring system in the mining area within a given time before and after the blasting;

[0014] The hydraulic support resistance change is: the change of the relevant statistical value of the hydraulic support resistance monitored by the mining area hydraulic support resistance monitoring system within a given time before and after the blasting;

[0015] The stress online monitoring changes are: changes in relevant statistical values ​​of stress magnitude monitored by borehole stress sensors arranged in the advanced stress concentration area of ​​the working face in the mining area within a given time before and after blasting.

[0016] Furthermore, the change of the microseismic energy is determined by calculating the change of the average value of the energy of the monitored microseismic events within a given time before and after the blasting. The calculation formula of the average value of the energy of the monitored microseismic events within a given time before and after the blasting is:

[0017]

[0018] In the formula, Q m Q is the average energy value of microseismic events monitored within a given period of time before blasting; m ' is the average energy value of the microseismic events monitored within a given period of time after the blasting; N m N is the number of microseismic events counted within a given time before blasting; m ' is the number of microseismic events counted within a given time after the blasting; Q i (i=1,2,3,...,N m ) is the energy of the corresponding microseismic event within a given time before blasting; Q i '(i=1,2,3,...,N m ') is the energy of the corresponding microseismic event within a given time after the blasting.

[0019] Furthermore, by calculating the change in the average value of the monitored hydraulic support working resistance within a given time before and after the blasting, the change in the resistance of the hydraulic support is determined; the calculation formula for the average value of the monitored hydraulic support working resistance within a given time before and after the blasting is:

[0020]

[0021]

[0022]

[0023] In the above formula, N s is the number of hydraulic supports selected for the main tunnel on one side; X is the drilling depth; Y is the length of land occupied by a single hydraulic support arrangement, so the number of hydraulic supports selected for the main tunnels on both sides is 2N s P Si Before blasting, 2N s The average working resistance of a hydraulic support in a given period of time; P Si 'After the blasting 2N s The average working resistance of a hydraulic support in a given period of time; P A To implement 2N before blasting s The average value of the working resistance of the hydraulic supports; P A 'To implement 2N after blasting s The average value of the working resistance of the hydraulic supports; N i N is the number of working resistance values ​​of a hydraulic support counted within a given time before blasting; i 'It is the number of working resistance values ​​of a hydraulic support counted within a given time after blasting.

[0024] Furthermore, by calculating the stress average value of the borehole stress sensor arranged in the advanced stress concentration area of ​​the working face within a given time before and after the blasting, the stress online monitoring change is determined; the calculation formula of the stress average value before and after the blasting is:

[0025]

[0026] Where P H P is the average value of stress online monitoring in the leading stress concentration area of ​​the working face within a given time before blasting; H ′ is the average value of stress online monitoring in the leading stress concentration area of ​​the working face within a given time after blasting; N H is the number of monitoring data of the drilling stress sensor in the advanced stress concentration area of ​​the working face; i Data monitored by a single borehole stress sensor within a given period of time before blasting; i ′ is the data monitored by a single borehole stress sensor within a given time after blasting.

[0027] Furthermore, the calculation formula for determining the importance index of each of the influencing factors is:

[0028]

[0029] In the formula, a ij is the importance ratio of the i-th element to the j-th element; a i is the importance level of the i-th element, a j is the importance level of the jth element, and the importance level is determined according to the quantified importance level range in the hierarchical analysis method.

[0030] Furthermore, the process of determining the pressure relief effect interval index of each of the influencing factors is as follows:

[0031] Calculate the changes in the relevant statistical indicators of each influencing factor within a given time before and after the blasting, and calculate the change rate. The calculation formula is as follows:

[0032]

[0033] Where ω is the rate of change, P0 is the value of the relevant statistical value within a given time before the blasting, and P1 is the value of the relevant statistical value within a given time after the blasting;

[0034] The pressure relief effect interval index corresponding to the calculated change rate is determined according to a predetermined indicator system.

[0035] Furthermore, the predetermined indicator system is:

[0036] When ω is between w1% and w2%, the pressure relief effect interval index is 1; when ω is between w2% and w3%, the pressure relief effect interval index is 4; when ω is between w3% and w4%, the pressure relief effect interval index is 8; when ω is between w4% and w5%, the pressure relief effect interval index is 16; when ω>w5%, the pressure relief effect interval index is 32; among which 0<w1<w2<w3<w4<w5.

[0037] Furthermore, the calculation model of the evaluation result is:

[0038]

[0039] Where C is the roof blasting pressure relief effect index, i.e. the evaluation result; n i is the weight factor obtained for each influencing factor, W i It is the pressure relief effect interval index of each influencing factor.

[0040] Furthermore, the grading of the coal mine roof blasting pressure relief effect according to the evaluation results includes:

[0041] When the roof blasting pressure relief effect index C is between m and 2m, the pressure relief effect is poor;

[0042] When the roof blasting pressure relief effect index C is between 2m and 4m, the pressure relief effect is medium;

[0043] When the roof blasting pressure relief effect index C is between 4m and 8m, the pressure relief effect is better;

[0044] When the roof blasting pressure relief effect index C is greater than 8m, the pressure relief effect is good;

[0045] Among them, the value of m is determined according to the geological conditions and mining conditions at the coal mine site.

[0046] It can be seen from the above technical scheme that, compared with the prior art, the present invention discloses a method for evaluating the effect of roof blasting unloading pressure based on the analytic hierarchy process, and the weight factors of different factors affecting the effect of roof blasting unloading pressure are obtained through the analytic hierarchy process, and based on the influencing factors, an interval index indicator system for the effect of roof blasting unloading pressure is established, and a roof blasting unloading pressure evaluation model is further established. According to the model calculation and the on-site geological conditions and mining conditions of the coal mine, the effect of roof blasting unloading pressure in deep coal mines is quantitatively evaluated, which plays a role in reducing the roof pressure step distance, energy during pressure and impact hazard during working face mining under hard roof conditions, and provides quantitative theoretical support for early warning and prevention of coal mine dynamic disasters, ensuring the effective implementation of mine safety production work. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0048] Figure 1 The present invention provides a flowchart of a method for evaluating the effect of roof blasting pressure relief based on the analytic hierarchy process. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] like Figure 1 As shown, the embodiment of the present invention discloses a method for evaluating the roof blasting pressure relief effect based on the hierarchical analysis method, comprising the following steps:

[0051] Step 1: Determine the factors that affect the effect of coal mine roof blasting pressure relief;

[0052] Step 2: Determine the importance index of each influencing factor and determine the weight of each influencing factor based on the hierarchical analysis method;

[0053] Step 3: Determine the pressure relief effect interval index of each influencing factor according to the changes of relevant statistical indicators of each influencing factor within a given time before and after the blasting;

[0054] Step 4: Perform weighted summation on the weights of various influencing factors and the pressure relief effect interval index to obtain an evaluation result;

[0055] Step 5: Classify the pressure relief effect of coal mine roof blasting based on the evaluation results.

[0056] In one embodiment, the influencing factors determined in step 1 include: changes in microseismic energy, changes in hydraulic support resistance, and changes in stress online monitoring;

[0057] The change of microseismic energy refers to the change of the relevant statistical value of the microseismic energy monitored by the microseismic monitoring system in the mining area within a given time before and after the blasting.

[0058] The change of hydraulic support resistance is: the change of relevant statistical values ​​of the hydraulic support resistance monitored by the hydraulic support resistance monitoring system in the mining area within a given time before and after the blasting;

[0059] The changes in stress online monitoring are: the changes in relevant statistical values ​​of stress within a given time before and after blasting as monitored by the borehole stress sensors arranged in the advanced stress concentration area of ​​the working face in the mining area.

[0060] Specific:

[0061] 1. The change of microseismic energy is determined by calculating the change of the average value of the energy of the monitored microseismic events within a given time before and after the blasting. The calculation formula for the average value of the energy of the monitored microseismic events within a given time before and after the blasting is:

[0062]

[0063] In the formula, Q m Q is the average energy value of microseismic events monitored within a given period of time before blasting; m ' is the average energy value of the microseismic events monitored within a given period of time after the blasting; N m N is the number of microseismic events counted within a given time before blasting; m ' is the number of microseismic events counted within a given time after the blasting; Q i (i=1,2,3,...,N m) is the energy of the corresponding microseismic event within a given time before blasting; Q i '(i=1,2,3,...,N m ') is the energy of the corresponding microseismic event within a given time after the blasting.

[0064] 2. Determine the change in resistance of the hydraulic support by calculating the change in the average value of the monitored working resistance of the hydraulic support within a given time before and after the blasting.

[0065] Calculate the change in the average value of the hydraulic support resistance within a given time before and after the blasting: select a certain number of hydraulic supports near the two tunnels to monitor their working resistance, and select the number of hydraulic supports according to the blasting drilling depth. The selection direction is to select in sequence from the main tunnel side to the coal body side. Among them, the number of hydraulic supports selected in one side of the main tunnel is as follows:

[0066]

[0067] Where N s is the number of hydraulic supports selected for the main tunnel on one side; X is the drilling depth; Y is the length of land occupied by a single hydraulic support. The number of hydraulic supports selected for the main tunnels on both sides is 2N s Calculate and obtain this 2N s The average resistance of a hydraulic support is:

[0068]

[0069]

[0070] In the above formula, N s is the number of hydraulic supports selected for the main tunnel on one side; X is the drilling depth; Y is the length of land occupied by a single hydraulic support arrangement, so the number of hydraulic supports selected for the main tunnels on both sides is 2N s P Si Before blasting, 2N s The average working resistance of a hydraulic support in a given period of time; P Si 'After the blasting 2N s The average working resistance of a hydraulic support in a given period of time; P A To implement 2N before blasting s The average value of the working resistance of the hydraulic supports; P A 'To implement 2N after blasting s The average value of the working resistance of the hydraulic supports; N i N is the number of working resistance values ​​of a hydraulic support counted within a given time before blasting; i'It is the number of working resistance values ​​of a hydraulic support counted within a given time after blasting.

[0071] 3. Determine the stress online monitoring change by calculating the average stress value of the borehole stress sensors arranged in the advanced stress concentration area of ​​the working face within a given time before and after blasting. The calculation formula is:

[0072]

[0073] Where P H P is the average value of stress online monitoring in the leading stress concentration area of ​​the working face within a given time before blasting; H ′ is the average value of stress online monitoring in the leading stress concentration area of ​​the working face within a given time after blasting; N H is the number of monitoring data of the drilling stress sensor in the advanced stress concentration area of ​​the working face; i Data monitored by a single borehole stress sensor within a given period of time before blasting; i ′ is the data monitored by a single borehole stress sensor within a given time after blasting.

[0074] In this embodiment, relevant data within 10 days before and after the blasting are counted.

[0075] In one embodiment, in step 2, the calculation formula for determining the importance index of each influencing factor is:

[0076]

[0077] In the formula, a ij is the importance ratio of the i-th element to the j-th element; a i is the importance level of the i-th element, a j is the importance level of the jth element, and the importance level is determined according to the quantified importance level range in the hierarchical analysis method.

[0078] Then, the weight of each factor is calculated based on the hierarchical analysis method. Specifically, the importance level of each influencing factor is determined according to the importance level scale based on the actual situation on site and expert opinions, and the importance level scale is given as shown in Table 1:

[0079] Table 1 Importance level scale

[0080] <![CDATA[Importance level a ij > explain 1 The i-th element and the j-th element are equally important. 3 The i-th element is slightly more important than the j-th element 5 The i-th element is more important than the j-th element 7 The i-th element is very important compared to the j-th element 9 The i-th element is extremely important compared to the j-th element 2,4,6,8 These four levels are the intermediate values ​​of the above levels.

[0081] According to the actual data on site, determine the importance level of the three influencing factors a ij, forming a judgment matrix. For example, according to the geological conditions and mining conditions of a mine and the opinions of experts, a1, a2 and a3 are determined to be the importance values ​​of microseismic, hydraulic support and stress online monitoring respectively. The judgment matrix of a mine is given as follows:

[0082]

[0083] According to the judgment matrix, the maximum eigenvalue λ is calculated max =3.0649, and perform consistency check on the eigenvector n0=(0.9628, 0.1067, 0.2483) to verify whether the matrix H has consistency or satisfactory consistency. If it does not have consistency, the matrix needs to be adjusted. If it meets the consistency requirements, the eigenvector is normalized to obtain the weight vector n=(0.7306, 0.0810, 0.1884) of each factor. The weight factor of the microseismic factor is n1=0.7306, the weight factor of the hydraulic support factor is n2=0.0810, and the weight factor of the stress online monitoring factor is n3=0.1884.

[0084] After determining the weights, the pressure relief effect interval index of each influencing factor needs to be calculated through step 3, specifically:

[0085] 1. Calculate the change rate of the three influencing factors, calculate the change of the relevant statistical indicators of each influencing factor within a given time before and after the blasting, and calculate the change rate. The calculation formula is as follows:

[0086]

[0087] Where ω is the rate of change, P0 is the value of the relevant statistical value within a given time before the blasting, and P1 is the value of the relevant statistical value within a given time after the blasting;

[0088] 2. Determine the pressure relief effect interval index corresponding to the calculated change rate based on a predetermined index system.

[0089] The predetermined indicator system is:

[0090] When ω is between w1% and w2%, the pressure relief effect interval index is 1; when ω is between w2% and w3%, the pressure relief effect interval index is 4; when ω is between w3% and w4%, the pressure relief effect interval index is 8; when ω is between w4% and w5%, the pressure relief effect interval index is 16; when ω>w5%, the pressure relief effect interval index is 32; among which 0<w1<w2<w3<w4<w5.

[0091] In a specific embodiment, step 4 includes:

[0092] The weights of each influencing factor and the pressure relief effect interval index are weighted and summed according to the following calculation model to calculate the evaluation results:

[0093]

[0094] Where C is the roof blasting pressure relief effect index, i.e. the evaluation result; n i is the weight factor obtained for each influencing factor, W i It is the pressure relief effect interval index of each influencing factor.

[0095] In step 5, when the roof blasting pressure relief effect index C is between m and 2m, the pressure relief effect is poor;

[0096] When the roof blasting pressure relief effect index C is between 2m and 4m, the pressure relief effect is medium;

[0097] When the roof blasting pressure relief effect index C is between 4m and 8m, the pressure relief effect is better;

[0098] When the roof blasting pressure relief effect index C is greater than 8m, the pressure relief effect is good;

[0099] Among them, the value of m is determined according to the geological conditions and mining conditions at the coal mine site.

[0100] In a specific example, based on the coal mine field data, the pressure relief effect intervals (index system) of the three influencing factors are given as shown in Table 2.

[0101] Table 2 Pressure relief effect interval table

[0102]

[0103] Combined with the pressure relief effect interval table given in Table 2, the pressure relief effect interval indexes of the three influencing factors are as follows: microseismic W1 = 4, hydraulic support W2 = 4, stress online monitoring W3 = 8. The roof blasting pressure relief effect index is calculated according to the weight vector:

[0104]

[0105] The blasting pressure relief effect classification of deep coal mine roof, where m∈[1,2], the specific value needs to be determined according to the geological conditions and mining conditions of the coal mine site. For example, if a mine has a hard roof and the working face crosses the fault, take m=1.25, and the pressure relief effect classification is as follows:

[0106] (1) When the roof blasting pressure relief effect index C is between 1.25 and 2.5, the pressure relief effect is poor;

[0107] (2) When the roof blasting pressure relief effect index C is between 2.5 and 5, the pressure relief effect is medium;

[0108] (3) When the roof blasting pressure relief effect index C is between 5 and 10, the pressure relief effect is better;

[0109] (4) When the roof blasting pressure relief effect index C is greater than 10, the pressure relief effect is good.

[0110] In the above example, the roof blasting decompression effect index is 4.7536, and the decompression effect is medium.

[0111] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0112] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for evaluating the effect of roof blasting pressure relief based on hierarchical analysis method, characterized in that: include: Determine the factors that affect the effect of coal mine roof blasting pressure relief; Determine the importance index of each of the influencing factors, and determine the weight of each of the influencing factors based on the hierarchical analysis method; Determine the pressure relief effect interval index of each of the influencing factors according to the changes in relevant statistical indicators of each of the influencing factors within a given time before and after the blasting; The weights of the influencing factors and the pressure relief effect interval index are weighted and summed to obtain an evaluation result; Based on the evaluation results, the coal mine roof blasting pressure relief effect is graded; The influencing factors include: changes in microseismic energy, changes in hydraulic support resistance and changes in stress online monitoring; The microseismic energy change is: the change of the relevant statistical value of the microseismic energy monitored by the microseismic monitoring system in the mining area within a given time before and after the blasting; The hydraulic support resistance change is: the change of the relevant statistical value of the hydraulic support resistance monitored by the mining area hydraulic support resistance monitoring system within a given time before and after the blasting; The stress online monitoring change is: the change of the relevant statistical value of the stress size monitored by the drilling stress sensor arranged in the advanced stress concentration area of ​​the working face in the mining area within a given time before and after the blasting; The process of determining the pressure relief effect interval index of each of the influencing factors is as follows: Calculate the changes in the relevant statistical indicators of each influencing factor within a given time before and after the blasting, and calculate the change rate. The calculation formula is as follows: Where ω is the rate of change, P0 is the value of the relevant statistical value within a given time before the blasting, and P1 is the value of the relevant statistical value within a given time after the blasting; The pressure relief effect interval index corresponding to the calculated change rate is determined according to a predetermined indicator system.

2. The method for evaluating roof blasting pressure relief effect based on analytic hierarchy process according to claim 1, characterized in that: The change of the microseismic energy is determined by calculating the change of the average value of the energy of the monitored microseismic events within a given time before and after the blasting. The calculation formula for the average value of the energy of the monitored microseismic events within a given time before and after the blasting is: In the formula, Q m Q is the average energy value of microseismic events monitored within a given period of time before blasting; m ' is the average energy value of the microseismic events monitored within a given period of time after the blasting; N m N is the number of microseismic events counted within a given time before blasting; m ' is the number of microseismic events counted within a given time after the blasting; Q i (i=1,2,3,...,N m ) is the energy of the corresponding microseismic event within a given time before blasting; Q i '(i=1,2,3,...,N m ') is the energy of the corresponding microseismic event within a given time after the blasting.

3. The method for evaluating roof blasting pressure relief effect based on analytic hierarchy process according to claim 1, characterized in that: The change of the hydraulic support resistance is determined by calculating the change of the average value of the monitored hydraulic support working resistance within a given time before and after the blasting. The calculation formula of the average value of the monitored hydraulic support working resistance within a given time before and after the blasting is: In the above formula, N s is the number of hydraulic supports selected for the main tunnel on one side; X is the drilling depth; Y is the length of land occupied by a single hydraulic support arrangement, so the number of hydraulic supports selected for the main tunnels on both sides is 2N s indivual; Before blasting, 2N s The average value of the working resistance of a hydraulic support among the hydraulic supports within a given time; After blasting 2N s The average working resistance of a hydraulic support in a given period of time; P A To implement 2N before blasting s The average value of the working resistance of the hydraulic supports; P A 'To implement 2N after blasting s The average value of the working resistance of the hydraulic supports; N i N is the number of working resistance values ​​of a hydraulic support counted within a given time before blasting; i 'It is the number of working resistance values ​​of a hydraulic support counted within a given time after blasting.

4. The method for evaluating roof blasting pressure relief effect based on analytic hierarchy process according to claim 1, characterized in that: By calculating the stress average value of the borehole stress sensor arranged in the advanced stress concentration area of ​​the working face within a given time before and after the blasting, the stress online monitoring change is determined; the calculation formula of the stress average value before and after the blasting is: Where P H P is the average value of stress online monitoring in the leading stress concentration area of ​​the working face within a given time before blasting; H ′ is the average value of stress online monitoring in the leading stress concentration area of ​​the working face within a given time after blasting; N H is the number of monitoring data of the drilling stress sensor in the advanced stress concentration area of ​​the working face; i Data monitored by a single borehole stress sensor within a given period of time before blasting; i ′ is the data monitored by a single borehole stress sensor within a given time after blasting.

5. The method for evaluating roof blasting pressure relief effect based on analytic hierarchy process according to claim 1, characterized in that: The calculation formula for determining the importance index of each of the influencing factors is: In the formula, a ij is the importance ratio of the i-th element to the j-th element; a i is the importance level of the i-th element, a j is the importance level of the jth element, and the importance level is determined according to the quantified importance level range in the hierarchical analysis method.

6. The method for evaluating roof blasting pressure relief effect based on analytic hierarchy process according to claim 1, characterized in that: The predetermined indicator system is: When ω is between w1% and w2%, the pressure relief effect interval index is 1; when ω is between w2% and w3%, the pressure relief effect interval index is 4; when ω is between w3% and w4%, the pressure relief effect interval index is 8; when ω is between w4% and w5%, the pressure relief effect interval index is 16; when ω>w5%, the pressure relief effect interval index is 32; among which 0<w1<w2<w3<w4<w5.

7. The method for evaluating roof blasting pressure relief effect based on analytic hierarchy process according to claim 1, characterized in that: The calculation model of the evaluation results is: Where C is the roof blasting pressure relief effect index, i.e. the evaluation result; n i is the weight factor obtained for each influencing factor, W i It is the pressure relief effect interval index of each influencing factor.

8. The method for evaluating roof blasting pressure relief effect based on analytic hierarchy process according to claim 7, characterized in that: According to the evaluation results, the coal mine roof blasting pressure relief effect is graded, including: When the roof blasting pressure relief effect index C is between m and 2m, the pressure relief effect is poor; When the roof blasting pressure relief effect index C is between 2m and 4m, the pressure relief effect is medium; When the roof blasting pressure relief effect index C is between 4m and 8m, the pressure relief effect is better; When the roof blasting pressure relief effect index C is greater than 8m, the pressure relief effect is good; Among them, the value of m is determined according to the geological conditions and mining conditions at the coal mine site.

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