| Coal and gas outburst is a serious dynamic disaster in coal mine production,which mainly occurs in the destruction zone of geological structure.Blasting technology is more and more widely used in coal mine production.However,in the actual application process,when the blasting stress wave disturbs the coal and rock in the geological structure area,it is easy to induce coal and rock gas dynamic disasters.In order to deeply explore the stability of coal and rock in the normal fault structure area disturbed by underground coal mine blasting operations,a blasting simulation test platform was built to carry out blasting similar simulation tests between normal coal seams and coal seams with normal faults.Combined with numerical simulation,the samples were compared and analyzed Crack propagation,stress changes and coal and rock failure laws;according to the test results and accident cases,the process and causes of coal and gas outburst dynamic disasters under the influence of blasting disturbance in the normal fault structure area are theoretically analyzed.The main conclusions reached are as follows:(1)Affected by the upper and lower coal seams of the fault,the maximum tensile stress in the vertical direction of the blasthole is 1.39 times that in the horizontal direction;the maximum tensile stress in the vertical direction of the blasthole in the faulted sample is 1.17 times that of the normal coal seam.By comparison,it is found that the stress curve of the fault-containing sample in the vertical direction of the blast hole is more complicated,the stress peak is larger,and the action time is longer.(2)Affected by the blasting stress,the crack growth state on the surface of the two samples is obviously different.The normal coal seam pattern develops and radiates outward with the blast hole as the center;the blast hole in the normal fault sample and the normal fault hanging wall coal seam The number and density of cracks in the direction of the blasthole are significantly more than in other directions.(3)It can be known by ultrasonic CT to detect the samples before and after the blasting,in the normal coal seam samples,the ultrasonic wave velocity of the detection surface passing the coal seam has a small decrease,which is a decrease of 18.78%;in the samples containing faults,the detection of the coal seam passing the bottom wall of the normal fault The surface ultrasonic wave velocity has dropped by 26.40%,and the detection surface ultrasonic wave velocity of the coal seam passing through the normal fault has dropped by 35.01%.It can be seen from the comparison that the damage to the coal seam with fault samples is more serious than the damage to the normal coal seam samples.(4)Numerical simulation found that the two models have obvious stress concentration at the junction of the coal and rock layers.In the normal fault model,affected by the normal fault structure,there is an obvious annular stress concentration around the blasthole under the coal layer.(5)Based on the test results,analyze the "4·4" large coal and gas outburst accident in the vertical shaft of Didaoshenghe Coal Mine.It is believed that the area where the accident occurred has the basic material basis and dynamic conditions for coal and gas outburst.During blasting and tunneling The cracks generated by blasting develop toward the upper and lower coal seams of normal faults,and the rock fissures,the coal seam fissures,and the fissures around the blasting holes interpenetrate each other;the blasting disturbance promotes the absorption of gas in the coal seam to analyze,and the broken coal rock provides a weak surface and gas flow for the occurrence of gas dynamic disasters.Passage,wind coal drilling construction disturbance affects the blasting area of the normal fault structure belt,which is an important reason for this type of coal and gas outburst accident.Figure[40]table[12]reference[77]... |
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