A comprehensive evaluation method for coal and rock mass damage grade determination of a coal mining face

Abstract

The application discloses a comprehensive evaluation method for coal and rock mass damage grade determination of a coal mining face, first collects microseismic signals during mining of the coal mining face, and determines damage areas; according to the collected microseismic signals, four microseismic indexes during mining of the damage areas are calculated respectively; according to the calculation results, determination results of the microseismic indexes on the damage areas are obtained; then, according to changes of the four index values during the whole mining stage, the entropy weight method is used to give weights of the microseismic indexes; based on the weights and the determination results of the indexes during mining of the damage areas, a comprehensive evaluation index Ψ of the damage areas is calculated; finally, according to the Ψ value, the coal and rock mass damage grade of each damage area is determined; therefore, the damage grade of the damage area in front of the coal mining face can be accurately evaluated, so as to guide implementation of targeted danger-removing measures according to the different damage grades after the evaluation, thereby reducing the probability and intensity of the dynamic disaster of the coal mining face, and ensuring the safety production of the coal mining face.

Description

Technical Field

[0001] This invention relates to a comprehensive evaluation method for determining the damage level of coal and rock mass in a coal mining face, belonging to the field of coal and rock mass damage monitoring and assessment technology. Background Technology

[0002] During coal face mining, pre-stress concentration occurs in the coal and rock mass within a 0-20m range ahead of the working face. This area, under the influence of periodic roof fracturing and disturbance from adjacent mining operations, forms a damaged zone with concentrated seismic sources. Furthermore, the complexity of the geological conditions and the difficulty of the mining techniques at the working face can lead to an expansion of this damaged zone and an intensification of the damage, rendering conventional stress relief and support measures inadequate and inducing dynamic disasters. Currently, the extent of the damaged zone caused by mining disturbance ahead of the working face is unclear, and the damage level is not accurately determined, making it impossible to implement targeted stress relief and support measures in advance, ultimately leading to dynamic disasters.

[0003] Therefore, one of the research directions in this industry is to provide a new method that can accurately assess the damage level of the damaged area in front of the working face, so as to guide the implementation of targeted mitigation measures based on different damage levels after assessment, thereby reducing the probability and intensity of dynamic disasters at the working face and ensuring safe production at the coal mining face. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a comprehensive evaluation method for determining the damage level of coal and rock mass in a coal mining face. This method can accurately assess the damage level of the damaged area in front of the working face, so as to guide the implementation of targeted mitigation measures based on different damage levels after assessment, thereby reducing the probability and intensity of dynamic disasters in the working face and ensuring safe production in the coal mining face.

[0005] To achieve the above objectives, the technical solution adopted by this invention is: a comprehensive evaluation method for determining the damage level of coal and rock mass in a coal mining face, the specific steps of which are as follows:

[0006] A. Deploy micro-vibration sensors at the coal mining face to collect micro-vibration signals during the mining process.

[0007] B. Locate the seismic source of the collected microseismic signals and determine the seismic source concentration area, that is, the various damaged areas formed under the disturbance of mining at the working face;

[0008] C. Based on the microseismic signals collected in step A, calculate the microseismic S value, microseismic b value, microseismic F value and microseismic Q value of each damaged area determined in step B during the mining process.

[0009] D. Based on the calculation results of the microseismic S-value, microseismic b-value, microseismic F-value, and microseismic Q-value during the mining process of each damaged area, the judgment results of each index value for each damaged area are denoted as θ. 1i θ 2i θ 3i θ 4i ;

[0010] E. Based on the changes in the four index values ​​of the damaged area during the entire mining stage, the entropy weight method is used to assign weights of λ1, λ2, λ3, and λ4 to the microseismic S value, microseismic b value, microseismic ΔF value, and microseismic Q value, respectively.

[0011] F. Calculate the comprehensive evaluation index Ψ of the damaged area based on the weights and judgment results of various indicators during the mining period of each damaged area.

[0012] G. The Ψ value calculated in step F determines the damage level of the coal and rock mass, specifically: ① When 0.3 < Ψ < 0.5, the result is a low damage level; ② When 0.5 ≤ Ψ < 0.7, the evaluation result is a medium damage level; ③ When 0.7 ≤ Ψ ≤ 1, the evaluation result is a high damage level.

[0013] Furthermore, the specific calculation process for each microseismic index in step C is as follows:

[0014] Microseismic S-value:

[0015]

[0016] Microseismic b-value:

[0017]

[0018] Microseismic F-value:

[0019]

[0020] Micro-vibration Q value:

[0021]

[0022] In the above formulas: N represents the number of microseismic signals collected during the working face mining period; M represents the magnitude of the microseismic signal; E represents the energy of the microseismic signal; M′ represents the maximum magnitude among all microseismic signals; T represents the time period for calculating each index; M i Indicates the Nth i The magnitude of the microseismic signal; E i Indicates the Nth i The energy of each microseismic signal; among which, the microseismic S value and microseismic F value are positively correlated with the degree of damage to the coal and rock mass, while the microseismic b value and microseismic Q value are negatively correlated with the degree of damage to the coal and rock mass.

[0023] Furthermore, the specific process of determining the weights of each microseismic index using the entropy weight method in step E is as follows:

[0024] The calculation results of the four indicators in the mining stage are normalized. The positive indicators, micro-seismic S value and micro-seismic F value, are processed according to formula (5), and the negative indicators, micro-seismic b value and micro-seismic Q value, are processed according to formula (6).

[0025] Positive indicators:

[0026]

[0027] Negative indicators:

[0028]

[0029] In the formula: a ij a represents the initial sample value. ij Let '' represent the standardized sample value. According to the definition of entropy in information theory, the weight λ of the j-th index of the i-th sample can be obtained. j for:

[0030]

[0031]

[0032]

[0033] In the formula: p ij e represents the weight of the j-th indicator in the i-th sample; j The entropy value of the j-th indicator of the i-th sample; n is the number of samples, y represents the number of indicators, which is 4 in this case; according to the above formula, the weight values ​​of λ1, λ2, λ3, and λ4 are calculated.

[0034] Furthermore, in step F, the comprehensive evaluation index Ψ of each damaged area is calculated according to formula (10):

[0035]

[0036] In the formula: θ imax This represents the maximum value of the judgment result (i.e., θ). 1max For θ 1i The maximum value within the range of values, θ 2max For θ 2i The maximum value within the range of values, θ 3max For θ 3i The maximum value within the range of values, θ 4max For θ 4i The maximum value within the range of values), the range of values ​​for Ψ is 0.3 < Ψ ≤ 1.

[0037] Furthermore, before microseismic location in step B, the source signals need to be screened to eliminate microseismic signals with energy less than 500J (and the screening threshold should be between 500J and 800J; the higher the environmental noise, the higher the screening threshold), to ensure that all microseismic signals are elastic waves released by the rupture of coal and rock mass, thereby accurately delineating the damaged area.

[0038] Furthermore, the determination of the damage area of ​​the coal mining face based on the microseismic S-value, microseismic b-value, microseismic F-value, and microseismic Q-value in step D needs to be combined with the established microseismic database of the coal mine (i.e., microseismic data of working faces that have been completely mined) to determine the value range of a single index in different damage level areas, thereby determining θ. i The value of θ is set as follows: The values ​​corresponding to low, medium, and high levels of damage based on a single indicator evaluation result are 1, 2, and 3, respectively. 1i θ 2i θ 3i θ 4i The range of values ​​for .

[0039] Furthermore, in step E, before the working face begins mining, the initial weights λ1, λ2, λ3, and λ4 of each indicator are calculated using the entropy weight method, based on the existing microseismic database of the coal mine (i.e., the microseismic data of the working face that has already been mined). Then, throughout the mining process, the microseismic data of the current working face is continuously added to the existing microseismic database, and the weights of each indicator are continuously recalculated using the entropy weight method, thereby updating the initial weights of each indicator in real time.

[0040] Compared with existing technologies, this invention first collects microseismic signals during the mining process of the working face and locates the seismic sources of the collected microseismic signals to determine the damaged areas. Based on the collected microseismic signals, the S-value, b-value, F-value, and Q-value of the microseismic signals during the mining process of the damaged areas are calculated. Based on the calculation results, the judgment results of each microseismic index for each damaged area are obtained. Then, based on the changes of the four index values ​​throughout the mining stage, the entropy weight method is used to assign weights to each microseismic index. Based on the weights of each index during the mining process of each damaged area and the judgment results, the comprehensive evaluation index Ψ of the damaged area is calculated. Finally, the damage level of the coal and rock mass in each damaged area is determined according to the Ψ value. Through the above process, this invention can accurately assess the damage level of the damaged area in front of the working face, so as to guide the implementation of targeted mitigation measures according to different damage levels after assessment, thereby reducing the probability and intensity of dynamic disasters at the working face and ensuring the safe production of the coal mining face. Attached Figure Description

[0041] Figure 1 This is an overall flowchart of the present invention;

[0042] Figure 2This is a schematic diagram of the damage area determined by microseismic positioning in this invention;

[0043] Among them, regions I to IV are four damage regions formed after screening microseismic signals;

[0044] Figure 3 This is a graph showing the evolution trend of the four microseismic indicators in each damage area in this invention;

[0045] Figure 4 This is a comprehensive evaluation result diagram determined using this invention during the longwall mining process. Detailed Implementation

[0046] The present invention will be further described below.

[0047] Example: In a certain mining area, dynamic manifestations occurred during coal face mining. To mitigate the impact of these dynamic hazards, the method of this invention was used to comprehensively evaluate the damage level of the preceding coal and rock mass, facilitating timely implementation of corresponding measures. Figure 1 As shown, the specific steps are as follows:

[0048] A. Deploy micro-vibration sensors at the coal mining face to collect micro-vibration signals during the mining process.

[0049] B. Before microseismic location, the seismic source signals need to be screened, eliminating those with energy less than 600J to ensure that all microseismic signals are elastic waves released from coal and rock mass ruptures; then, the collected microseismic signals are used for source location to determine the source concentration area, i.e., the damage areas I to IV formed under the disturbance of the working face mining. Figure 2 As shown;

[0050] C. Based on the microseismic signals collected in step A, calculate the microseismic S-value, microseismic b-value, microseismic F-value, and microseismic Q-value for each damaged area determined in step B during the mining process; such as Figure 3 As shown, the specific calculation process for each of the microseismic indices is as follows:

[0051] Microseismic S-value:

[0052]

[0053] Microseismic b-value:

[0054]

[0055] Microseismic F-value:

[0056]

[0057] Micro-vibration Q value:

[0058]

[0059] In the above formulas: N represents the number of microseismic signals collected during the working face mining period; M represents the magnitude of the microseismic signal; E represents the energy of the microseismic signal; M′ represents the maximum magnitude among all microseismic signals; T represents the time period for calculating each index; M i Indicates the Nth i The magnitude of the microseismic signal; E i Indicates the Nth i The energy of each microseismic signal; among which, the microseismic S value and microseismic F value are positively correlated with the degree of damage to the coal and rock mass, while the microseismic b value and microseismic Q value are negatively correlated with the degree of damage to the coal and rock mass.

[0060] D. Based on the calculation results of microseismic S-values, microseismic b-values, microseismic F-values, and microseismic Q-values ​​during the mining process in the damaged area, and combined with the established microseismic database of the coal mine (i.e., microseismic data from the mined-out working faces), determine the value range of a single index in different damage level areas, thereby determining θ. i The value of each indicator value is denoted as θ; the results of the determination of the damaged area based on the value of each indicator are recorded as θ. 1i θ 2i θ 3i θ 4i The values ​​corresponding to low, medium, and high levels of damage in the single indicator evaluation results are set to 1, 2, and 3, respectively, which are θ. 1i θ 2i θ 3i θ 4i The range of values ​​for is as shown in Table 1 in this embodiment.

[0061] Table 1: Correspondence between four indicator values, damage levels, and weights

[0062]

[0063] E. Before the start of longwall mining, the initial weights λ1, λ2, λ3, and λ4 of various indicators are calculated using the entropy weight method, based on the existing microseismic database of the coal mine (i.e., microseismic data from longwall faces that have already been mined). In this embodiment, the values ​​shown in Table 1 are used. Subsequently, throughout the entire longwall mining process, the microseismic data from the current longwall mining operation is continuously added to the existing microseismic database. Figure 3 The system uses real-time microseismic data and continuously recalculates the weights of various indicators using the entropy weight method, thereby updating the initial weights of each indicator in real time. The specific process of determining the weights of each microseismic indicator using the entropy weight method is as follows:

[0064] The calculation results of the four indicators in the mining stage are normalized. The positive indicators, micro-seismic S value and micro-seismic F value, are processed according to formula (5), and the negative indicators, micro-seismic b value and micro-seismic Q value, are processed according to formula (6).

[0065] Positive indicators:

[0066]

[0067] Negative indicators:

[0068]

[0069] In the formula: a ij a represents the initial sample value. ij Let '' represent the standardized sample value. According to the definition of entropy in information theory, the weight λ of the j-th index of the i-th sample can be obtained. j for:

[0070]

[0071]

[0072]

[0073] In the formula: p ij e represents the weight of the j-th indicator in the i-th sample; j The entropy value of the j-th indicator of the i-th sample; n is the number of samples, y represents the number of indicators, which is 4 in this case; according to the above formula, the weight values ​​of λ1, λ2, λ3, and λ4 are calculated.

[0074] F. Based on the weights and judgment results of various indicators during the mining period in each damaged area, calculate the comprehensive evaluation index Ψ of each damaged area according to formula (10):

[0075]

[0076] In the formula: θ imax This represents the maximum value of the judgment result, i.e., θ. 1max For θ 1i The maximum value within the range is 3, and similarly, θ 2max θ 3max , and θ 4max All are 3, and the value of Ψ is 0.3 < Ψ ≤ 1.

[0077] G. The Ψ value calculated in step F determines the damage level of the coal and rock mass, specifically: ① When 0.3 < Ψ < 0.5, the result is a low damage level; ② When 0.5 ≤ Ψ < 0.7, the evaluation result is a medium damage level; ③ When 0.7 ≤ Ψ ≤ 1, the evaluation result is a high damage level. Different treatment measures are adopted for different damage levels. The comprehensive evaluation results of this embodiment are as follows: Figure 4As shown in the figure, a total of 5 dynamic manifestations occurred during the mining process of this working face. Using the method of this invention, 4 of them were evaluated as high-level damage, and 1 was evaluated as medium-level damage (close to high-level damage). Actual monitoring showed that 5 high-level damage dynamic manifestations occurred during this period. The accuracy rate of the evaluation results of this invention reached 80%, thus proving that this invention can accurately evaluate the damage level of the coal and rock mass of the working face. Subsequently, the damage level evaluation will be carried out in real time using the method of this invention. After obtaining the damage level, targeted mitigation measures will be implemented to reduce the probability and intensity of dynamic disasters at the working face and ensure safe production at the coal mining face.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A comprehensive evaluation method for determining the damage level of coal and rock mass in a coal mining face, characterized in that, The specific steps are as follows: A. Deploy micro-vibration sensors at the coal mining face to collect micro-vibration signals during the mining process; B. Locate the seismic sources of the collected microseismic signals and determine the seismic source clusters, i.e., the various damage areas formed under the disturbance of mining operations at the working face. C. Based on the microseismic signals collected in step A, calculate the microseismic S value, microseismic b value, microseismic F value and microseismic Q value of each damaged area determined in step B during the mining process. D. Based on the calculation results of the microseismic S-value, microseismic b-value, microseismic F-value, and microseismic Q-value during the mining process of each damaged area, the judgment results of each index value for each damaged area are denoted as θ. 1i θ 2i θ 3i θ 4i ; E. Based on the changes in the four index values ​​of the damaged area throughout the entire mining stage, the entropy weight method is used to assign weights of λ1, λ2, λ3, and λ4 to the microseismic S value, microseismic b value, microseismic ΔF value, and microseismic Q value, respectively. The specific process is as follows: The calculation results of the four indicators in the mining stage are normalized. The positive indicators, micro-seismic S value and micro-seismic F value, are processed according to formula (5), and the negative indicators, micro-seismic b value and micro-seismic Q value, are processed according to formula (6). Positive indicators: （5） Negative indicators: （6） In the formula: Indicates the initial sample value. This represents the standardized sample value; according to the definition of entropy in information theory, the weight λ of the j-th index of the i-th sample can be obtained. j for: （7） （8） （9） In the formula: e represents the weight of the j-th indicator in the i-th sample; j The entropy value of the j-th indicator of the i-th sample; n is the number of samples, y represents the number of indicators, which is 4 in this case; according to the above formula, the weight values ​​of λ1, λ2, λ3, and λ4 are calculated respectively. F. Based on the weights and judgment results of various indicators during the mining process in each damaged area, calculate the comprehensive evaluation index for each damaged area. Ψ ; G, calculated in step F Ψ The value is used to determine the damage level of coal and rock mass, specifically: ① When 0.3 < Ψ <0.5, the result is a low damage level; ②0.5≤ Ψ <0.7, the evaluation result is medium damage level; ③0.7≤ Ψ ≤1 indicates a high damage level.

2. The comprehensive evaluation method for determining the damage level of coal and rock mass in a coal mining face according to claim 1, characterized in that, The specific calculation process for each microseismic index in step C is as follows: Microseismic S-value: （1） Microseismic b-value: （2） Microseismic F-value: （3） Micro-vibration Q value: （4） In the above formulas: N represents the number of microseismic signals collected during the working face mining period; M represents the magnitude of the microseismic signal; and E represents the energy of the microseismic signal. The maximum magnitude among all microseismic signals; T represents the time interval for calculating each index; M i Indicates the Nth i The magnitude of the microseismic signal; E i Indicates the Nth i The energy of each microseismic signal; among which, the microseismic S value and microseismic F value are positively correlated with the degree of damage to the coal and rock mass, while the microseismic b value and microseismic Q value are negatively correlated with the degree of damage to the coal and rock mass.

3. The comprehensive evaluation method for determining the damage level of coal and rock mass in a coal mining face according to claim 1, characterized in that, Step F calculates the comprehensive evaluation index of each damaged area according to formula (10). Ψ : （10） In the formula: θ imax This indicates the maximum value of the judgment result. Ψ The value range is 0.3 < Ψ ≤1.

4. The comprehensive evaluation method for determining the damage level of coal and rock mass in a coal mining face according to claim 1, characterized in that, Before microseismic location in step B, the source signals need to be screened to remove microseismic signals with energy less than 500J, ensuring that all microseismic signals are elastic waves released by the rupture of coal and rock mass, thereby accurately delineating the damaged area.

5. The comprehensive evaluation method for determining the damage level of coal and rock mass in a coal mining face according to claim 1, characterized in that, In step D, the determination of the damage area of ​​the coal mining face based on the microseismic S-value, microseismic b-value, microseismic F-value, and microseismic Q-value needs to be combined with the microseismic database already established in the coal mine to determine the value range of a single index in different damage level areas, thereby determining θ. i The value; The values ​​corresponding to low, medium, and high levels of damage in the single indicator evaluation result are set to 1, 2, and 3, respectively, which are θ. 1i θ 2i θ 3i θ 4i The range of values ​​for .

6. The comprehensive evaluation method for determining the damage level of coal and rock mass in a coal mining face according to claim 1, characterized in that, In step E, before the working face begins mining, the initial weights λ1, λ2, λ3, and λ4 of each indicator are calculated using the entropy weight method, based on the existing microseismic database of the coal mine. Then, throughout the mining process, the microseismic data of the current working face mining is continuously added to the existing microseismic database, and the weights of each indicator are continuously recalculated using the entropy weight method, thereby updating the initial weights of each indicator in real time.

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