Research On Stress Control And Disaster Prevention Technology For Mining Rock Mass Under Extremely Thick Key Layers

In some coal mines in China,there is generally one or more layers of extremely thick sandstone layers in the roof of coal measures,which seriously affects the development and distribution of coal gas migration channels.The presence of typical thick key layers can cause changes in gas migration channels and supporting stresses in working faces,which can easily lead to coal seam gas outburst and cause a series of mine dynamic disasters,whether they are broken or not.Based on the background of middling coal and gas outburst accident in the process of machine roadway excavation in Ⅱ 1026 working face of Haizi Coal Mine,this thesis studies the causes and prevention of coal and gas outburst dynamic disasters in the roadway under the extremely thick key layer by using theoretical analysis,numerical simulation,field measurement and other methods.The main achievements are as follows:(1)The physical and mechanical properties of giant thick igneous rock in mining area Ⅱ 102 were tested in the laboratory,the stress distribution characteristics of giant thick igneous rock were theoretically analyzed,and the influence of the presence or absence of giant thick igneous rock on the abutment pressure of coal bodies was simulated and studied.The results show that after mining in Working Face 1024 of Mining Area 102,the local area of the bottom interface of the extremely thick igneous rock has entered a yielding state,and the intermediate layer is still in an elastic state,with only a small amount of overall bending and subsidence.At this time,the load of the extremely thick igneous rock and its upper layer will shift towards the coal bodies on both sides,resulting in a high concentration of bearing stress in the lateral solid coal,The peak value of vertical stress and the influence range of stress are significantly larger than the simulation results under the condition of no extremely thick igneous rock.(2)A gas solid coupling seepage model of elastic deformation coal is established to simulate and study the laws of gas migration,permeability,and deformation of coal under different vertical stress loading conditions.The results show that gas is mainly concentrated in the upper and lower ends of the roadway wall;The natural release rate of coal gas is fast,and the gas pressure first increases sharply and then decreases rapidly in the early stage,and then decreases sharply and then slowly in the later stage;By changing the distribution of the main stress and the permeability of the coal body,the huge thick igneous rock rapidly develops and penetrates the cracks in the coal body,thereby promoting the rapid release of gas pressure in the coal body into the interior of the roadway,causing coal and gas outburst.(3)Based on the working conditions of Haizi Coal Mine,a grouting filling scheme was proposed and field engineering practice was carried out.The results show that the pier pillar successfully transmits the stress of the solid coal to the goaf,and the larger the diameter of the pier pillar,the larger stress peak value,the wider stress distribution,the more obvious the transfer effect,and the more significant the reduction of the stress of the surrounding rock in the stope and the stress of the roadway coal.The thesis has 50 figures,9 tables,and 106 references.