| With the increase of coal mining depth and intensity,rock burst has become one of the serious disasters in mines,and mining protective layer is one of the effective methods to control coal and gas protrusion and impact mine pressure.The second layer of coal mined by Haishiwan Coal Mine in Gansu Province is a coal seam with coal and gas outburst and impact tendency,and large-energy mine seismic events occur frequently when mining the upper protective layer oil layer A layer6115 oil shale face.In order to grasp the law of mine seismic activity and the disaster problems that may be induced by it,the thesis uses on-site measurement,theoretical analysis and numerical simulation to study the law of mine seismic activity,the structure of overburden rock and the stress energy change law of the working face during mining,and the progress of the thesis is as follows:The physical and mechanical parameters of oil shale were determined,and its rock burst tendency was identified.The results show that the elastic energy criterion of oil shale rock burst is weak rock burst tendency,and the impact energy criterion and brittle rock burst index are both non-rock burst tendency.The seismic activity law of the 6115 oil shale face of Haishiwan Coal Mine was analyzed.The results show that the number and energy level of mine earthquakes also change with the advancement of the working face.In the early stage of mining,most of the ore earthquake was concentrated at the floor of the working face,and as the working face advanced,the position of the mine earthquake moved up and concentrated at the top plate.The middle and late stages of the recovery of large-energy ore earthquakes began to increase,mainly located in the advanced area of the working face,within 100 m of the roof above the oil shale layer.The study revealed the overburden structure and evolution law of oil shale face.The position of the key layer in the overlying rock layer of the oil shale and the height of the water-conducting fracture zone after recovery were calculated.After oil shale mining,the overlying rock layer presents the structural form of "masonry beam",the roof plate presents the fracture form of "O-X" in the layer direction,and the long-arm "F" structure of the main key layer is presented vertically in the working face.The influence of the buried depth,overlying structure change and surface subsidence on the earthquake was analyzed.The stress and energy evolution law during oil shale face reproduction,the influence of coal seam recovery on oil shale face and the effect of oil shale mining on pressure reduction and energy reduction of coal mining face were studied.The simulation results are:(1)with the gradual increase of the advanced supporting pressure of the working face,the phenomenon of stress and energy accumulation occurs on the solid oil shale side;(2)Due to the long distance between the coal mining face and the oil shale face,the exploitation of the coal seam below has a greater impact on the goaf behind the oil shale face,so that the stress recovery is faster;The stress and energy at the cutting eye gradually increased with the remining of the second layer of coal,but had little effect on the stress in the leading area of the working face.(3)After oil shale mining,when the coal seam face below is recovered,its advanced supporting stress and energy density are significantly reduced.According to the above research results,the rock burst risk of oil shale face mining was evaluated,and a prevention and control scheme for strong ore seismic and strong mineral pressure of oil shale face was designed,including advanced regional fracturing in the 6116 face corresponding to the frequent occurrence of strong ore in the 6115 working face.For the 6116 working face return air trough and transportation trough that have not been remined,a trend cutting top blasting and tendency pre-cracking blasting scheme are proposed,and pre-cracking blasting is carried out on the cut eye.This thesis has 87 figures,21 tables,and 93 references... |
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