| A large number of literature materials show that there are often residual coal pillars in the protective layer when mining multiple coal seams,which will affect the safety of coal mine production.The stress level in the 903 working face of Daxing Coal Mine is relatively high under the superimposed influence of residual coal pillars above the cut hole and the goaf on both sides of the working face Therefore,this paper takes the 903 working face of Daxing Coal Mine as the research object.According to the on-site mining situation,717 is analyzed by theoretical analysis and numerical simulation Legacy of 719 face the 903 island coal face in different coal pillar stoping period of the stope stress distribution,and analyses the microseismic events during the mining face distribution characteristics and laws,and finally puts forward the 903 face a more scientific and reasonable monitoring plan,and the prevention and control in the process of mine mining face application effect is good,the following conclusions:(1)Under conditions of 903 working face of geological structure,the theory analysis of the goaf left 903 isolated island working face under the coal pillar impact risk influence factors and key stratum structure characteristics Results show: the 903 mining face in danger have effect on the main control factors of goaf legacy and 717 719 working face of coal pillar on both sides of the mined-out area of stress concentration effects;According to the calculation results of the fracture distance of key strata,the hard strata of the 12 th layer of the roof of 903 working face were broken,while the third hard strata were not broken.(2)By analyzing the stress distribution characteristics of surrounding rock during mining in 903 working face,combined with FLAC3 D numerical simulation results of 903 isolated working face,the following conclusions are obtained: the overall stress level in the area near the cut-off of working face is low,but due to the influence of coal pillars left between 7 coal mined-out areas,the local cut-off is in a state of stress concentration;Affected by the boundary of the overlying goaf,there is obviously higher stress concentration in the corresponding range of the two roadways,and the first "square" stage of the working face is within the influence range of the boundary of the overlying goaf.In addition,the lateral supporting pressure of the 902 goaf and the 905 goaf makes the working face dangerous.During the second and third times of "square" of the working face,the stress increased in different degrees,and the impact risk increased accordingly.When the mining reaches the narrow face stage of the working face,the stress gradually shifts to the section coal pillar with the advancing of the working face,and the corner area of the coal pillar is the stress concentration area,so the impact risk is high.When the working face is mined near the stop mining line,with the expansion of goaf area,the leading bearing pressure in front of the coal wall shows a downward trend,and the peak stress begins to shift to the coal wall near the stop mining line.Meanwhile,due to the arrangement of the stop mining line in 905 working face,the stress concentration occurs in the transportation gateway near the stop mining line 905,and the irregular stop mining line will increase the impact risk of roadway,so pressure relief and anti-impact measures should be taken in advance.(3)Because the 903 working face is located under the liberated layer of the 717 and 719 working faces,there are some sections of coal pillars,so that as long as the working face has a certain space of mined-out areas,the roof of the working face will collapse in time.In addition,the isolated island working face which is mined-out on both sides makes the impact risk increase during mining,and the mine earthquakes are mainly distributed in the area in front of the advancing position.During the "square" period of 903 working face,the microseismic events are mainly distributed within 200 m ahead of the advancing position in the strike direction and within 150 m in the dip direction.(4)Combined with the impact risk analysis of 903 working face,the active prevention or passive avoidance technology for dynamic load source and static load source of impact is put forward,and the active and passive control technology for weakening of rock burst is formed by combining the two,and the method of monitoring and early warning for static and dynamic load respectively is put forward.Drilling cuttings method and stress on-line monitoring are used as monitoring and early warning methods of static load force source;The techniques of microseismic regional monitoring and seismic wave CT early warning are the main methods of dynamic load monitoring and early warning,and the comprehensive application of various monitoring means is an effective means of monitoring and early warning of rock burst in 903 working face under special mining geological conditions.And timely effect inspection,to ensure that the impact risk coefficient of working face is significantly reduced.The research conclusion of this paper can provide scientific and effective guidance for the safety production of 903 isolated island working face,and also provide certain theoretical support and technical guidance for the safety mining of similar mine working face.There are 76 figures,13 tables and 94 references in this paper. |
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