A method for evaluating impact danger of a stoping face

Abstract

This invention relates to the field of rockburst hazard assessment technology for underground coal mine working faces, specifically a method for assessing rockburst hazard in longwall mining faces, comprising: (1) determining the assessment object, including its geological and mining technical conditions and scope; (2) conducting factor analysis based on factors affecting rockburst hazard; (3) assigning values ​​to all influencing factors according to a factor value table; (4) calculating the assessment indicators; and (5) comparing the calculated values ​​of the assessment indicators with the critical indicators to determine the rockburst hazard level of the working face. This invention solves the problems of existing assessment methods failing to accurately identify the overall rockburst hazard level of the working face and failing to comprehensively analyze geological and mining technical conditions, resulting in errors in the rockburst hazard level assessment. It can assess the overall rockburst hazard level during longwall mining, improving the accuracy of the macroscopic assessment results of rockburst hazard level and providing a basis for rockburst prevention and control during longwall mining.

Description

Technical Field

[0001] This invention relates to the field of impact hazard assessment technology for underground coal mine working faces, and in particular to a method for assessing impact hazard in longwall mining faces. Background Technology

[0002] With the increasing depth of underground coal mining, rockbursts have become one of the major hazards threatening coal mining. Rockbursts are characterized by their sudden onset, numerous influencing factors, and complexity, posing significant challenges to disaster prevention and control. According to incomplete statistics, the intensity of rockbursts occurring at longwall faces is greater than during tunneling due to the greater disturbance caused by mining. If the geological conditions of the area where the longwall face is located can be basically understood before mining begins, and the mining technology conditions are clearly defined, accurate rockburst hazard assessments can be conducted, and preventative measures can be taken in advance based on the assessment results, effectively avoiding rockburst accidents.

[0003] Currently, the comprehensive index method, multi-factor method, and probability index method are commonly used in the assessment of rockburst hazard in my country. For example, CN103362551A discloses a comprehensive index assessment method for rockburst, which includes: (1) analyzing the types of geological influencing factors W among the influencing factors of rockburst. gi Determine the maximum hazard index R for various types of geological influencing factors. mgi And the actual hazard index Rgi, calculate the rockburst hazard index W for geological influencing factors. t1 =ΣR gi / R mgi (2) Analysis of the types of mining-related influencing factors among the factors affecting rockburst. mj Determine the maximum hazard index R for various types of mining influencing factors. mmj And the actual risk index R mj Calculate the rock pressure hazard index W of mining-related influencing factors. t2 =ΣR mj / R mmj (3) Determine the final comprehensive index of rockburst risk as W. t =max{W t1 W t2};(4) Comprehensive index of rockburst risk W t The higher the value, the higher the risk level of rock pressure in the mining area.

[0004] However, this method separates the geological factors and mining technology factors that affect rockburst, failing to consider the impact of different mining technology factors on rockburst risk under the same geological conditions. Furthermore, it does not consider the relationship between the self-weight stress of the overburden and the strength of the coal body, the relationship between the increase in the thickness of the caving zone and the thickness of the mined coal seam, the relationship between the location of the working face roadway and the lateral support pressure of the adjacent goaf, and the relationship between the distance of the designed stop line from the goaf and the range of mining disturbance. Therefore, its rockburst risk assessment results need to be further improved, especially in longwall mining faces with clear geological and mining technology conditions.

[0005] In summary, the accuracy of existing comprehensive index assessment methods for rockburst is not yet fully sufficient to meet the needs of rockburst risk assessment in longwall mining faces. Summary of the Invention

[0006] To address the problem that existing comprehensive index assessment methods for rockburst cannot accurately predict the rockburst hazard level of longwall mining faces, this invention proposes a rockburst hazard assessment method for longwall mining faces that can meet the on-site needs of various mines, in order to improve the accuracy of rockburst hazard prediction for longwall mining faces and thus more effectively guide rockburst prevention and control.

[0007] Specifically, this application provides the following technical solution:

[0008] A method for assessing the impact hazard of a longwall mining face includes the following steps:

[0009] (1) Determine the evaluation object and scope

[0010] Based on the geological description of the working face, the layout parameters of the longwall mining face are determined, and then the object of the impact hazard assessment is determined and the scope of the impact hazard assessment is defined.

[0011] (2) Analyze the influencing factors of rockburst on the evaluation object

[0012] Based on the research and summary of the factors affecting rockburst, it has been determined that the factors affecting the rockburst risk of the longwall mining face include at least 20 factors as shown in Table 1 below.

[0013] Table 1 Factors affecting rockburst at the longwall mining face

[0014]

[0015] (3) Values ​​of factors affecting rockburst

[0016] Based on the value table of each influencing factor provided in Table 2, values ​​were assigned to each geological and mining technology influencing factor of rockburst.

[0017] Table 2. Values ​​of Influencing Factors of Rockburst in Longwall Mining Face

[0018]

[0019]

[0020]

[0021] (4) Calculation of evaluation indicators

[0022] Based on the values ​​of various influencing factors of rockburst obtained in step (3), according to The evaluation indexes are calculated to obtain the final result W.

[0023] (5) Determination of rockburst hazard level

[0024] Based on the relationship between the W result and the rockburst hazard level discrimination criteria, the rockburst hazard level of the working face is determined. W∈[0,0.25] indicates no rockburst hazard, W∈(0.25,0.5] indicates a weak rockburst hazard, W∈(0.5,0.75] indicates a moderate rockburst hazard, and W∈(0.75,1] indicates a strong rockburst hazard.

[0025] In steps (3) and (4), values ​​are assigned to each rockburst influencing factor, and the geological factors and mining technology factors affecting rockburst are comprehensively considered and normalized.

[0026] Among them, the "ratio of overburden self-weight stress to coal uniaxial compressive strength" is a factor affecting rockburst. It takes into account the relationship between the self-weight stress of the overburden formed by the coal seam burial depth and the uniaxial compressive strength of the coal body, and no longer takes the factors separately based on the coal seam burial depth and the uniaxial compressive strength of the coal body.

[0027] Among them, the factor affecting rockburst, "the ratio of the increase in thickness of the caving zone rock strata after caving to the thickness of the mined coal seam", takes into account the relationship between the increase in thickness of the caving zone rock strata after caving and the thickness of the mined coal seam. That is, the supporting effect of the overlying strata on the overlying strata after caving. At the same time, it is supplemented for the filling mining face which is conducive to rockburst prevention and control.

[0028] Among them, the impact factor of rockburst, "the relationship between the location of the working face roadway and the lateral support pressure of the adjacent goaf", can be determined based on the working face layout plan and the stress environment of the area, which can more accurately reflect the rockburst risk of the working face under complex conditions.

[0029] Among them, the ratio of the distance between the designed stop line and the goaf to the mining disturbance range is a factor affecting rock bursts. The value of the factor affecting the designed stop line can be determined based on the actual mining conditions and the estimated mining disturbance range. This avoids the difference in the distance between the stop line and the goaf under different coal seam thicknesses, mining intensities and overlying strata structures, and can improve the accuracy of rock burst risk assessment.

[0030] Among them, the factor affecting rockburst, "width of coal pillar formed by fault cutting outside the working face", can be determined based on the fault parameters exposed during the working face tunneling and the coal pillar formed between the working face roadway. This supplements the influence of faults not mined in the working face and the coal pillar formed by the working face roadway on rockburst at the working face, which can improve the accuracy of rockburst risk assessment.

[0031] Among them, the factor affecting rockburst, "width of coal pillar formed by roadway cutting outside the working face", can be determined based on the coal pillar formed between the old roadways around the working face and the working face roadway. This supplements the impact of coal pillars formed between the old roadways and the working face roadway that are not mined in the working face on rockburst of the working face, which can improve the accuracy of rockburst risk assessment.

[0032] Among them, the rockburst influencing factor "the width of the coal pillar between the location of the roadway / fault cutting within the working face and the stop-mining position of the working face" can be determined based on the coal pillar formed between the old roadway (or fault) and the working face cut, which supplements the influence of the coal pillar (or isolated coal body) formed by the old roadway (or fault) and the working face cut within the coal body being mined on the rockburst of the working face, and can improve the accuracy of rockburst risk assessment.

[0033] Compared with the prior art, the method for assessing the impact hazard of longwall mining faces of the present invention has at least the following beneficial effects:

[0034] (1) The method for evaluating the impact risk of longwall mining face of the present invention takes advantage of the clear geological and mining technical conditions of longwall mining face, and comprehensively considers the geological factors and mining technical factors that affect rockburst, avoiding the error caused by considering factors separately. After each influencing factor is taken separately, it is normalized and then the rockburst risk level is determined, thereby improving the accuracy of rockburst risk evaluation of longwall mining face.

[0035] (2) The method for evaluating the rockburst risk of the longwall mining face of the present invention analyzes at least 20 possible influencing factors in the longwall mining face, which makes up for the loopholes and omissions of the existing methods. The evaluation method is more targeted and greatly improves the accuracy and reliability of the rockburst risk level evaluation of the longwall mining face.

[0036] The method for evaluating the impact hazard of the longwall mining face according to the present invention will be further explained below with reference to the accompanying drawings. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating the method for assessing the impact hazard of the longwall mining face according to the present invention. Detailed Implementation

[0038] like Figure 1 As shown, taking the 1309S longwall face of a certain mine as an example, the method for assessing the impact hazard of the longwall face includes the following steps:

[0039] (1) Determine the evaluation object and scope

[0040] The evaluation object is the 1309S longwall face, and the evaluation scope is the coal body of the longwall face and the coal body within 100m around it.

[0041] (2) Analyze the influencing factors of rockburst on the evaluation object

[0042] Based on the factors affecting rockburst in Table 2, we analyze the impact of each factor on rockburst at the 1309S longwall face.

[0043] The number of rockbursts at the same level and in the same coal seam in the W1:1309S longwall face was 0.

[0044] The W2:1309S longwall face has a mining depth of 440m to 640m, a uniaxial compressive strength of 12.12MPa, and a ratio of the self-weight stress of the overlying strata to the uniaxial compressive strength of the coal of 1.32.

[0045] There is a 10.03m thick medium sandstone layer 38.15m above the coal seam in the W3:1309S longwall face, and the uniaxial compressive strength of this rock layer is 68MPa, which is a thick and hard rock layer.

[0046] W4: The coal seam thickness of the 1309S working face is 2.19m, the coal wall width of the working face is 300m, and there is a 1310S goaf (160m wide) along the goaf. The thickness of the caving zone is calculated as 4 times the mining height (coal thickness). The caving zone swelling coefficient is taken as 1.2. Then the ratio of the increase in the thickness of the caving zone strata swelling to the thickness of the mined coal seam is 0.8.

[0047] The maximum principal stress in the area where the W5:1309S working face is located is 22.64 MPa, and the vertical stress is 11.42 MPa; σ hmax =22.64MPa, σ h =14.85MPa, γ=51%.

[0048] The impact energy index of coal at the W6:1309S working face is 2.26.

[0049] The elasticity index of coal in the W7:1309S working face is 2.72.

[0050] The dynamic failure time of coal at the W8:1309S working face is 173.4 ms.

[0051] W9:1309S working face is not within the protective layer of coal seam 9, and the degree of pressure relief of the protective layer is average.

[0052] W 10 This factor was not involved.

[0053] W 11 The 1309S working face has the 1310S goaf on one side and solid coal on the other.

[0054] W 12 The coal face width of the 1309S working face is 300m, and the coal pillar width between the transport roadway and the 1310S goaf is 2.5m. Both roads of the working face are in low-stress zones, less than 1.5σ. c .

[0055] W 13 The width of the coal pillar between the 1309S working face and the 1310S goaf is 2.5m.

[0056] W 14 The 1309S working face has two roadways with trapezoidal roadway layouts where the roof is broken and the bottom is broken. The bottom corners of the low side walls have bottom coal with a thickness of less than 1m.

[0057] W 15 Based on the three-zone load theory, the estimated range of disturbance impact of mining at the 1309S working face is 115m, and the distance between the stop mining line and the goaf in the advancing direction is greater than 500m.

[0058] W 16 During the mining period, the 1309S working face did not advance into areas of coal seam erosion, coal seam merging, or thickness changes.

[0059] W 17 Several small faults with elevation differences of less than 3m were actually exposed in the 1309S transport roadway, and the DF3 fault with an elevation difference of 0-14m was exposed in the 1309S track roadway. The DF1 fault with an elevation difference of 0-5m exists in the central area of ​​the working face.

[0060] W 18 The 1309S track roadway revealed the DF3 fault with a drop of 0-14m, extending from the solid coal side of the working face to the inside of the working face.

[0061] W 19 This factor was not involved.

[0062] W 20The 1309S working face is affected by faults such as DF1 and DF3, and the working face has been mined through the cutting area; there is a connecting roadway in the working face, and the working face has been mined through the connecting roadway.

[0063] The 1309S working face is free from influencing factors such as folds and aquifers.

[0064] (3) Values ​​of factors affecting rockburst

[0065] Based on the analysis results of each influencing factor in step (2), the values ​​of each rockburst and mining technology influencing factor are shown in Table 3.

[0066] Table 3. Values ​​of Factors Affecting Rockburst in the 1309S Longwall Face

[0067]

[0068]

[0069]

[0070] (4) Calculation of evaluation indicators

[0071] Based on the values ​​of various influencing factors of rockburst obtained in step (3), according to The evaluation index was calculated, and the final result of W was 0.444.

[0072] (5) Determination of rockburst hazard level

[0073] Based on the relationship between the W result and the rockburst hazard level discrimination standard, the rockburst hazard level of the working face is determined. W∈(0.25,0.5] indicates a weak rockburst hazard, meaning that the 1309S longwall face has a weak rockburst hazard.

[0074] The method of this invention utilizes existing rockburst influencing factors in longwall mining faces to evaluate rockburst risk. Common rockburst influencing factors include at least 20 types listed in Table 1. This embodiment only uses common conditions as examples. The evaluation of specific longwall mining faces needs to be supplemented and reduced as necessary based on the actual geological and mining conditions of the working face.

[0075] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method of evaluating the impact danger of a stope face, characterized by: Comprising the following steps: (1) Determine the evaluation object and range; (2) Analyze the impact factors of rock burst of the evaluation object: the factors affecting the rock burst danger of the mining working face at least include 20 factors shown in the following table, (3) Rock burst impact factor value: value each rock burst geological and mining technology impact factor; Among them, each rock burst impact factor is valued according to the following table; (4) Evaluation index calculation According to the values of each influencing factor of rock burst obtained in step (3), the evaluation index is calculated according to and the final result is obtained W . (5) Rock burst danger grade discrimination According to W The relationship between the results and the rock burst danger grade determination standard determines the rock burst danger grade of the working face; wherein, W ∈[0, 0.25] is no rock burst danger, W ∈(0.25, 0.5] is weak rock burst danger, W ∈(0.5, 0.75] is medium rock burst danger, W ∈(0.75, 1] is strong rock burst danger.

2. The stope face impact danger assessment method of claim 1, wherein: The step (1) is specifically, according to the working face geological specification, the layout parameters of the mining working face are determined, and then the object of the rock burst danger evaluation is determined, and the rock burst danger evaluation range is delimited.

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