Coal seam impact tendency testing method based on mining dynamics

Abstract

The invention discloses a coal seam impact tendency testing method based on mining dynamics. The method comprises the following steps: 1, preparing a fracture coal seam impact tendency sample and fitting an impact tendency index; 2, acquiring mining-induced stress field distribution characteristics of the coal seam to be mined; and 3, correcting the impact tendency index. The method comprises the following steps: carrying out grouping test on samples according to a coal sample fracture dominant development angle to obtain a quantitative relation between a sample impact tendency index and the coal sample fracture dominant development angle; the mining-induced stress direction change trend at the maximum principal stress peak position is obtained, a test scheme is designed on the basis of mining-induced stress distribution characteristics, and finally the coal seam impact tendency is tested by introducing the coal seam joint fissure occurrence and the coupling effect of the mining-induced stress and the fissure of the coal seam to be mined into the coal seam impact tendency test. A method for correcting the impact tendency grade of the fractured coal seam is provided; and the test accuracy and reliability are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of mining engineering, and particularly relates to a coal seam impact tendency test method based on mining dynamics. BACKGROUND

[0002] Rock burst refers to the dynamic failure phenomenon caused by the violent release of accumulated elastic strain energy of the coal and rock mass around the coal mining face under high stress conditions. With the continuous increase of the depth and intensity of coal mining, rock burst disasters gradually increase, which seriously threatens the safe mining of coal resources in China. At present, in the rock burst prevention and control system of coal mines, coal seam impact tendency identification is required before mining in rock burst mines, so as to further take monitoring and early warning and rock burst prevention measures. Impact tendency identification is of great significance to ensure the safety production of rock burst mines.

[0003] The geological occurrence and mining technical conditions of coal seams are complex and changeable, and the stress distribution characteristics of coal seams under different conditions have obvious differences. Current researches mainly focus on the size of mining stress, and there are few studies on the mechanical response of coal and rock mass after the change of mining stress direction. Due to the widespread distribution of a large number of original joint fissures in the natural coal body, the existence of fissures makes the coal sample present obvious uneven and discontinuous characteristics, and its mechanical characteristics have obvious discrete type under the action of mining stress. The traditional impact tendency identification method only uses the methods of "randomly selecting coal samples" or "uniformly distributing sampling points" to prepare samples, without considering the coupling relationship between the fissure occurrence and the mining stress direction, which leads to great discreteness of the test results of coal samples at different positions in the same coal seam, and it is difficult to accurately reflect the real impact tendency of the coal seam, which misleads the rock burst prevention and control decision. Therefore, under the condition of coal seam fissure development, the impact tendency test should comprehensively consider various factors such as mining stress size, stress direction and fissure occurrence. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a coal seam impact tendency test method based on mining dynamics to solve the problems in the prior art. The test sample is grouped according to the dominant development angle of the coal sample fissure, the quantitative relationship between the impact tendency index of the test sample and the dominant development angle of the coal sample fissure is obtained, the change trend of the mining stress direction at the position of the maximum principal stress peak value is obtained, the combined action of the mining stress size and direction is considered, the test scheme is designed based on the mining stress distribution characteristics, and finally the coupling action of the coal seam joint fissure occurrence, the mining stress and the fissure of the coal seam to be mined is introduced into the coal seam impact tendency test, and a correction method for the impact tendency grade of the fissured coal seam is proposed. The problem of great discreteness of the test results of each group in the same coal seam caused by the uncontrolled angle between the loading direction and the fissure in the traditional test method is avoided, and the accuracy and reliability of the test are improved.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is: a coal seam impact tendency testing method based on mining dynamics, which comprises the following steps: Step one, prepare a fractured coal seam impact tendency sample and fit the impact tendency index, the process is as follows: Step 101, sampling in a coal seam stable roadway area where the coal seam is stable and not affected by mining, the number of coal blocks at each sampling site is not less than 2, and the spatial position relationship between the coal blocks and the roadway should be marked when sampling; wherein the size of the sampled coal blocks is not less than the design size, and the length, width and height of the design size are 25cm, 25cm and 20cm respectively; Step 102, processing the sampled coal blocks, dividing the coal blocks into multiple samples, the diameter of each sample is 50mm, and the height of each sample is 100mm; performing uniaxial compression test on the processed samples; scanning the internal joint fissure distribution state of each sample by using CT scanning technology during the test to obtain the coal sample fissure dominant development angle of each sample; wherein the coal sample fissure dominant development angle is based on the vertical plane of the sampled coal seam stable roadway as the reference plane; Step 103, according to the coal sample fissure dominant development angle of each sample, the samples are divided into seven groups at intervals of 15°, and the coal sample fissure dominant development angle of each group of samples is 0°, 15°, 30°, 45°, 60°, 75° and 90° respectively; wherein the number of samples in each group is not less than 10; Step 104, loading each group of samples on a rigid testing machine at a rate of 0.05MPa / s until failure, while drawing the stress-strain curve of each sample throughout the process; calculating the elastic energy index , impact energy index , dynamic failure time , and uniaxial compressive strength of each sample according to the stress-strain curve, and classifying the samples according to the coal impact tendency classification standard; Step 105, according to the classification results of the coal impact tendency classification standard, linear fitting is performed on each type of sample to obtain the quantitative relationship between the sample impact tendency index and the coal sample fissure dominant development angle ; ; ; ; wherein, , , , , , , , , , , , and are fitting coefficients; Step two, obtaining the stress field distribution characteristics of the coal seam to be mined, the process is as follows: Step 201, using stress relief method to test the initial ground stress at the selected test site of the coal seam to be mined, and obtaining the initial ground stress test data; wherein, the initial ground stress test data includes the size and direction of the initial ground stress , , and ; wherein, , , and respectively represent the maximum principal stress, the intermediate principal stress and the minimum principal stress at each measuring point; Step 202, establishing a mine exploitation model according to the geological conditions and mining parameters of the selected coal seam to be mined; and combining the initial ground stress test data in step 201, establishing a coal seam mining stress evolution numerical model; Step 203, according to the actual mining situation of the coal seam to be mined, carrying out excavation calculation on the coal seam mining stress evolution numerical model, simulating and analyzing the spatial distribution characteristics and concentration degree of the principal stress in the mining process of the coal seam to be mined, mastering the peak value distribution position of the maximum principal stress of the coal seam to be mined, and extracting the normal stress values , and , and the shear stress values , and at the peak value position of the maximum principal stress; Step 204, according to the normal stress values and shear stress values at the peak value position of the maximum principal stress extracted, calculating the direction cosine of the maximum principal stress after deflection, and then obtaining the angle between the maximum principal stress and the horizontal plane of the roadway, denoted as ɑ, that is, the maximum principal stress angle at the peak value position of the maximum principal stress under the influence of mining; Step three, correcting the impact tendency index: according to the angle between the maximum principal stress and the horizontal plane of the roadway obtained in step 204, obtaining the loading direction, and then taking the fracture dominant surface as the reference surface, obtaining the angle between the fracture dominant surface and the peak value of the maximum principal stress under the influence of mining , substitute into the formula of step 105, and obtain the impact tendency index of the coal seam to be mined under the actual stress condition, that is, the elastic energy index , the impact energy index , the dynamic failure time , and the uniaxial compressive strength .

[0006] Further, in step 102, when the processed sample is subjected to uniaxial compression test, the angle between the loading direction and the crack dominant surface needs to be controlled to make the sample form the grouping angle in step 103.

[0007] Further, in step 201, when the test site of the selected coal seam to be mined is selected, the test site needs to avoid the influence range of faults, fracture zones and goaf according to the occurrence conditions and mining technical conditions of the coal seam to be mined; and at least four measuring points need to be arranged at the test site, and the drilling depth is greater than 15m.

[0008] Further, in step 203, the actual mining conditions of the coal seam to be mined include the mining method of the coal seam to be mined, the working face parameters of the coal seam to be mined, and the advancing speed of the coal mining machine.

[0009] Compared with the prior art, the present application has the following advantages: 1. The present application groups the samples according to the crack dominant development angle of the coal sample to obtain the quantitative relationship between the sample impact tendency index and the crack dominant development angle of the coal sample, avoids the problem that the traditional test method does not control the angle between the loading direction and the crack, which leads to the large dispersion of the test results of each group in the same coal seam, and improves the accuracy and reliability of the test.

[0010] 2. The present application obtains the stress direction change trend of the mining stress at the position of the maximum principal stress peak under the influence of the mining of the coal seam to be mined, comprehensively considers the combined action of the mining stress size and direction, designs the test scheme based on the mining stress distribution characteristics, is widely applicable to the impact tendency test of the coal seam under different conditions, and effectively improves the accuracy of the test results.

[0011] 3. The present application introduces the occurrence of the coal seam joint crack and the coupling action of the mining stress and the crack of the coal seam to be mined into the impact tendency test of the coal seam, and proposes a correction method for the impact tendency grade of the cracked coal seam.

[0012] In summary, the present application groups the samples according to the crack dominant development angle of the coal sample to obtain the quantitative relationship between the sample impact tendency index and the crack dominant development angle of the coal sample; obtains the stress direction change trend of the mining stress at the position of the maximum principal stress peak, comprehensively considers the combined action of the mining stress size and direction, designs the test scheme based on the mining stress distribution characteristics, finally introduces the occurrence of the coal seam joint crack and the coupling action of the mining stress and the crack of the coal seam to be mined into the impact tendency test of the coal seam, and proposes a correction method for the impact tendency grade of the cracked coal seam; avoids the problem that the traditional test method does not control the angle between the loading direction and the crack, which leads to the large dispersion of the test results of each group in the same coal seam, and improves the accuracy and reliability of the test.

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0014] Fig. 1 This is a schematic diagram showing the distribution of internal joints and fissures in the sample of the present invention.

[0015] Fig. 2 This is a schematic diagram showing the positional relationship of the dominant development angle of fractures in the coal sample of the present invention.

[0016] Fig. 3 This is a schematic diagram showing the positional relationship between the angle between the dominant fracture surface and the peak value of the maximum principal stress under the influence of mining.

[0017] Fig. 4 This is a flowchart of the method of the present invention. Detailed Implementation

[0018] like Figs. 1 to 4 The method for testing coal seam impact tendency based on mining dynamics, as shown, includes the following steps: Step 1: Prepare impact tendency samples from fractured coal seams and fit impact tendency indices. The process is as follows: Step 101: Take samples in the stable roadway area of ​​the coal seam where the coal seam is stable and unaffected by mining. The number of coal blocks at each sampling point shall not be less than 2 blocks, and the spatial relationship between the coal blocks and the roadway shall be marked during sampling. The size of the sampled coal blocks shall not be less than the design size, wherein the length, width and height of the design size are 25cm, 25cm and 20cm respectively. Step 102: Process the sampled coal block into multiple specimens, each with a diameter of 50 mm and a height of 100 mm. Perform a uniaxial compression test on the processed specimens. During the test, use CT scanning technology to scan the distribution of internal joints and fractures in each specimen to obtain the dominant fracture development angle for each specimen. Among them, the dominant development angle of fractures in coal samples The vertical plane of the sampled stable roadway of the coal seam is used as the reference plane; Step 103: Based on the dominant development angle of fractures in each coal sample The samples were divided into seven groups at 15° intervals, and the dominant development angle of coal fractures in each group was determined. The angles are 0°, 15°, 30°, 45°, 60°, 75°, and 90°, respectively; and each group contains no fewer than 10 samples. Step 104, each group of samples is respectively loaded axially on a rigid testing machine at a rate of 0.05 MPa / s until failure, while the stress-strain curve of each sample is drawn throughout; the elastic energy index of each sample is calculated according to the stress-strain curve , impact energy index , dynamic failure time , uniaxial compressive strength , and according to the impact tendency classification standard of coal, the samples are classified; Step 105, according to the classification results of the impact tendency classification standard of coal, linear fitting is performed on each type of sample to obtain the quantitative relationship between the impact tendency index of the sample and the dominant development angle of the coal sample fracture as ; ; ; ; Wherein, , , , , , , , , , , , and are fitting coefficients; Step two, obtain the stress field distribution characteristics of the coal seam to be mined, the process is as follows: Step 201, the initial ground stress test data are obtained by using stress relief method to test the initial ground stress at the selected test site of the coal seam to be mined; wherein, the initial ground stress test data include the size and direction of the initial ground stress , , and ; wherein, , , and respectively represent the maximum principal stress, the intermediate principal stress and the minimum principal stress at each measuring point; Step 202, according to the geological conditions and mining parameters of the selected coal seam to be mined, a mine mining model is established; and combined with the initial ground stress test data in step 201, a coal seam mining stress evolution numerical model is established; Step 203, according to the actual mining situation of the coal seam to be mined, the coal seam mining stress evolution numerical model is calculated, the spatial distribution characteristics and concentration degree of the principal stress in the mining process of the coal seam to be mined are simulated and analyzed, the peak value distribution position of the maximum principal stress of the coal seam to be mined is mastered, and the normal stress values , and , and the shear stress values at the peak value position of the maximum principal stress are extracted 、 and ; Step 204, according to the maximum principal stress peak position extracted from the normal stress value and the shear stress value, the direction cosine after the deflection of the maximum principal stress is calculated, and then the angle between the maximum principal stress and the horizontal plane of the roadway is obtained, which is denoted as ɑ, that is, the maximum principal stress angle at the maximum principal stress peak position under the influence of mining; Step three, correcting the impact tendency index: according to the angle between the maximum principal stress and the horizontal plane of the roadway obtained in step 204, the loading direction is obtained, and then the angle between the fracture advantage surface and the maximum principal stress peak under the influence of mining is obtained based on the fracture advantage surface as the reference surface , which is substituted into the formula of step 105 to obtain the impact tendency index of the coal seam to be mined under the actual stress condition, that is, the elastic energy index , impact energy index , dynamic failure time , uniaxial compressive strength . .

[0019] The present application obtains the quantitative relationship between the impact tendency index of the sample and the fracture advantage development angle of the coal sample by grouping the sample according to the fracture advantage development angle of the coal sample, avoids the problem that the angle between the loading direction and the fracture is not controlled in the traditional test method, which leads to the large dispersion of the test results of the same coal seam, and improves the accuracy and reliability of the test.

[0020] The present application obtains the stress direction change trend of the maximum principal stress peak position under the influence of mining, comprehensively considers the combined action of the stress size and direction, and designs the test scheme based on the stress distribution characteristics, which is widely applicable to the impact tendency test of the coal seam under different conditions, and effectively improves the accuracy of the test results.

[0021] The present application introduces the occurrence of the coal seam joint fracture and the coupling effect of the mining stress and the fracture of the coal seam to be mined into the impact tendency test of the coal seam, and proposes a correction method for the impact tendency grade of the fractured coal seam.

[0022] In actual use, in step 104, the elastic energy index , impact energy index , dynamic failure time , uniaxial compressive strength of each sample are calculated, and then the coal is classified according to the impact tendency classification standard of the coal.

[0023] Table 1: Coal impact tendency classification standard

[0024] It should be noted that coal mine rock burst usually occurs in the mining stress concentrated roadway, different coal seam occurrence conditions and mining technical conditions lead to different mining stress size and direction, and the mechanical response characteristics of coal body under different stress environment are significantly different, therefore, when identifying the coal seam rock burst tendency, the mining stress field characteristics generated by coal seam mining should also be fully considered. The purpose is to accurately quantify the high risk area of rock burst, that is, the deflection angle of the maximum principal stress peak position relative to the original ground stress, which is the key to get the real stress direction of coal body.

[0025] In step two, the mining stress field distribution characteristics of the coal seam to be mined include the size and direction of mining force stress; in step 202, according to the geological conditions and mining parameters of the target mine, the finite difference software FLAC3D is used to establish the mining model of the mine, the physical and mechanical parameters of the rock mass are set, the initial ground stress test data in step 201, that is, the three-dimensional stress field environment of the mine, is inputted, and the coal seam mining stress evolution numerical model is established, which provides a basic model for subsequent basic numerical calculation of coal seam mining stress after mining.

[0026] In step 204, the normal stress value and shear stress value at the peak position of the maximum principal stress extracted are imported into Matlab software, according to the basic theory of spatial problem in elasticity mechanics, the angle between the maximum principal stress and the horizontal plane of the roadway is finally calculated, which is the core basis for the correction direction of the subsequent test results. In step 204, the principal stress direction is calculated according to the stress state of the extracted model unit, the direction cosine value of the principal stress of the coal body to be mined under the influence of mining disturbance in X, Y and Z axes is obtained, and then the angle between the maximum principal stress and the horizontal plane of the roadway, that is, the maximum principal stress angle at the peak position of the maximum principal stress under the influence of mining, is obtained; the calculation formula is as follows: ; wherein, in the formula: is the principal stress, wherein i=1, 2, 3, respectively representing the maximum principal stress, the intermediate principal stress and the minimum principal stress; , and are the stress components of the principal stress in X, Y and Z directions respectively; , and are the direction cosine values.

[0027] In step three, the angle between the loading direction and the fracture dominant surface is the fracture dominant development angle of the coal sample of the coal seam to be mined, that is, .

[0028] In particular, a large number of scholars at home and abroad have shown that the stress concentration area under mining disturbance has the highest impact risk, and the influence of mining stress is not considered in the conventional impact tendency test, so the mining stress and the occurrence of coal seam fissures are introduced into the impact tendency test, which can make the test results closer to the actual situation, and also can reduce the dispersion of the test results caused by the occurrence of coal seam fissures.

[0029] In this embodiment, in step 102, when the uniaxial compression test of the processed sample is carried out, the angle between the loading direction and the fissure dominant surface needs to be controlled, so that the sample can form the grouping angle in step 103.

[0030] In this embodiment, in step 201, when the test site of the selected coal seam to be mined is selected, the occurrence conditions and mining technical conditions of the coal seam to be mined are needed to be selected, and the test site needs to avoid the influence range of faults, fracture zones and goaf; and at least 4 measuring points need to be arranged at the test site, and the drilling depth is greater than 15m.

[0031] In actual use, at least 4 measuring points need to be arranged at the test site, in order to cover the roof and floor of the coal seam and the lateral surrounding rock.

[0032] In this embodiment, in step 203, the actual mining conditions of the coal seam to be mined include the mining method of the coal seam to be mined, the working face parameters of the coal seam to be mined, and the advancing speed of the coal mining machine.

[0033] The above is only a preferred embodiment of the present application, and does not limit the present application, any simple modification, change and equivalent structure change according to the technical essence of the present application to the above embodiment are still within the protection scope of the technical scheme of the present application.

Claims

1. A method for testing the burst tendency of a coal seam based on mining dynamics, characterized in that, The method comprises the following steps: Step one, preparation of a sample of a fractured coal seam and fitting of the impact tendency index, the process is as follows: Step 101, sampling in a stable roadway region of a coal seam that is stable and not affected by mining, the number of coal blocks at each sampling site is not less than 2, and the spatial positional relationship between the coal blocks and the roadway should be marked when sampling; wherein the size of the sampled coal blocks is not less than the design size, and the length, width and height of the design size are 25 cm, 25 cm and 20 cm respectively; Step 102, processing the sampled coal block, dividing the coal block into multiple samples, each sample having a diameter of 50mm, and each sample having a height of 100mm; performing a uniaxial compression test on the processed samples; during the test, scanning the internal joint fissure distribution state of each sample using CT scanning technology to obtain a coal sample fissure dominant development angle of each sample; wherein the coal sample fissure dominant development angle is based on a vertical plane of the stable roadway of the sampled coal seam as a reference plane. Step 103, according to the crack dominant development angle of each sample The samples are divided into seven groups at intervals of 15°, and the crack dominant development angles of the samples in each group are 0°, 15°, 30°, 45°, 60°, 75° and 90° respectively; wherein the number of samples in each group is not less than 10. ​ Step 104, respectively loading each group of samples on a rigid testing machine at a rate of 0.05 MPa / s until failure, while drawing the stress-strain curve of each sample throughout the process; calculating the elastic energy index of each sample according to the stress-strain curve , impact energy index , dynamic failure time , uniaxial compressive strength , and classifying the samples according to the impact tendency classification standard of coal; Step 105, according to the classification results of the impact tendency classification standard of coal, linear fitting is carried out on each type of sample to obtain the quantitative relationship between the impact tendency index of the sample and the dominant development angle of the fracture of the coal sample as ; ; ; ; wherein , , , , , , , , , , , and are fitting coefficients; Step two, obtaining the stress field distribution characteristics of the coal seam to be mined, the process is as follows: Step 201, using stress relief method to test the initial ground stress at the selected testing site of the coal seam to be mined, and obtaining initial ground stress test data; wherein, the initial ground stress test data includes the size and direction of the initial ground stress , , ; wherein, , , respectively represent the maximum principal stress, the intermediate principal stress and the minimum principal stress at each measuring point. Step 202, according to the selected geological conditions and mining parameters of the coal seam to be mined, a mine mining model is established; and combined with the initial stress test data in step 201, a coal seam mining stress evolution numerical model is established; Step 203, according to the actual mining situation of the coal seam to be mined, the excavation calculation of the coal seam mining stress evolution numerical model is carried out, the spatial distribution characteristics and concentration degree of the principal stress in the mining process of the coal seam to be mined are simulated and analyzed, the distribution position of the maximum principal stress peak value of the coal seam to be mined is mastered, and the normal stress value at the position of the maximum principal stress peak value is extracted 、 and , and the shear stress value 、 and ​ Step 204, according to the normal stress value and shear stress value at the position of the maximum principal stress peak value, the direction cosine after the deflection of the maximum principal stress is calculated, and then the angle between the maximum principal stress and the horizontal plane of the roadway is obtained, denoted as ɑ, that is, the maximum principal stress angle at the position of the maximum principal stress peak value under the influence of mining; Step three, correct the impact tendency index: according to the angle between the maximum principal stress obtained in step 204 and the roadway horizontal plane, the loading direction is obtained, and then the angle between the fracture advantage surface and the maximum principal stress peak value under the influence of mining is obtained with the fracture advantage surface as the reference surface , the substitute into the formula of step 105, get the impact tendency index of the coal seam to be mined under the actual stress condition , impact energy index , dynamic failure time , uniaxial compressive strength .

2. The coal seam burst tendency test method based on mining dynamics according to claim 1, characterized in that: In step 102, when performing uniaxial compression test on the processed sample, the angle between the loading direction and the dominant fracture surface needs to be controlled to make the sample form the grouping angle in step 103.

3. The coal seam burst tendency test method based on mining dynamics according to claim 1, characterized in that: In step 201, when selecting the test site of the coal seam to be mined, the test site needs to be selected according to the occurrence conditions and mining technical conditions of the coal seam to be mined, and the test site needs to avoid the influence range of faults, fracture zones and goaf; and at least 4 measuring points need to be arranged at the test site, and the drilling depth is greater than 15 m.

4. The coal-seam burst-tendency test method based on mining dynamics according to claim 1, characterized in that: In step 203, the actual mining conditions of the coal seam to be mined include the mining method of the coal seam to be mined, the working face parameters of the coal seam to be mined, and the advancing speed of the coal mining machine.

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