Study On The Prevention And Control Of Rock Burst In Hard Roof Of Stope Based On Weak Structure

The roof of 36#coal seam,one of the main coal seams in Dongbaowei coal mine,is hard rock.The left working face of No.1 mining area-750 is a goaf with hard and thick roof,and there is a suspended roof structure on the side of the goaf along the upper trough;The third mining area-620 left working face is a wide pillar roadway stope,with the pillar width of 20-25m in the stage,resulting in the accumulation of coal seam energy around the roadway.There is a high risk of rock burst in both stopes.In this paper,the above two stopes are taken as the research object,and the theoretical analysis,numerical simulation and field test are used to study the mechanism of rockburst,the characteristics of rockburst and the technology of controlling rock burst of weak structure,and the engineering application is carried out.(1)According to the occurrence condition of coal seam in the working face,the mechanical model of rockburst is established based on the analysis of the influencing factors of rockburst;The peak value of the stress along the gob is close to the side of the roadway,which has the distribution characteristics of strong impact risk.The mechanism of rock burst is as follows:The fracture movement of the side hanging roof under the mining disturbance drives the impact of the coal body.The engineering cause is the sudden release of the elastic energy of the roadway side under the action of high stress.The high stress of the near empty chute in the wide pillar stope is caused by the superposition of the lateral high stress and the traction stress of the suspended roof.The mechanism of the rockburst is that the elastic energy is released suddenly under the coupling action of the high stress of the wide pillar and the additional high stress of the suspended roof structure.(2)Using RFPA numerical simulation software,the process of deformation and failure of coal mass under the condition of no(small)coal pillar hanging roof stope and large coal pillar protecting roadway stope is studied;The stress distribution and energy evolution of coal seam under different conditions of roof suspension and pillar width are analyzed.The existence of the suspended roof makes the energy of the surrounding rock close to the goaf(within 11m)accumulate,and the energy of the rockburst appears at the working face side of the roadway;After the implementation of the weak structure,the energy is transferred from the shallow coal body to the deep coal body of about 17?28 m,and the rockburst energy is greatly dissipated.The simulation results of stopes with different width coal pillars show that:in the case of small coal pillars within 15m,the coal pillars are completely destroyed,and there is no impact risk along the goaf;in the case of 40m coal pillars,the stress is concentrated on the wide coal pillars,and the impact risk along the goaf is low;in the case of 25m coal pillars,the stress concentration around the goaf is high,and the impact risk is high.(3)According to the occurrence mechanism and appearance characteristics of rockburst on hard roof,the mechanical model of rockburst prevention and control based on engineering weak structure body is established.Combined with the stope conditions of no(small)coal pillar hanging roof and wide coal pillar protecting roadway in Dongbao coal mine 36 coal seam,it is put forward and formed,including hanging roof detection and broken roof,roadway undercover and expanding,engineering unit body,engineering weak structure body and its coupling structure body Anti scour technology system.(4)According to the geological mining conditions of no(small)pillar hanging roof stope-750 left working face in 36 coal seam,the control technology and technological parameters of engineering weak structure composed of roof defect body,coal seam cavernous body,roadway side protection body and support body are designed;according to the geological mining conditions of large pillar protecting roadway stope-620 left working face in 36 coal seam,the control technology and technological parameters of roof defect body and coal seam double side sea are designed Control technology and process parameters of weak structure composed of soft body,strong support body of roadway side and other units.The above technical system has been applied in two stopes,effectively controlling the rockburst and ensuring the safe mining of the working face.