Study On Prevention And Control Of Dynamic Pressure In Shallow Buried Gap

The Shendong mining area is a typical shallow-buried short-distance coal seam group mining area in China.In the early stage of mining development,traditional room-pillar mining was used to form a large number of column goafs.Due to the sudden instability of the coal pillars in the overlying goaf due to the coal seam mining under the close coal seam,it poses a serious safety hazard to the lower coal seam mining.In this paper,the 30105 working face in the gaping goaf of Nanliang Coal Mine is taken as the research object.The theoretical analysis,physical similarity simulation,numerical simulation and field measurement are used to analyze the concentrated load of the separated goaf to the close coal seam.Systematic research on the formation of dynamic loads and the techniques of dynamic pressure prevention during the breaking process of roof during mining.Based on the theoretical analysis,the structural mechanics model of the"uniform load beam"of the key layer in front of the concentrated coal pillar is established,which reveals that the breaking of the "uniform load beam"is the mechanism that causes the strong mine pressure to occur,it is called Hair area.When the working face exits the coal pillar,the key block is unstable and the hinge structure is formed.The load of the overlying rock layer acting on the hinge structure is directly transmitted to the bracket.The impact on the bracket is the root cause of the dynamic rail pressure.This position is dynamic,it is called Mine pressure zone.Through physical similarity simulation experiments,it is shown that when the concentrated coal pillar is not weakened,the force of the"uniform load beam"transmitted to the coal pillar and the coal pillar 7m is transmitted to the bracket and the strong ore pressure and the force acting on the joint are transmitted to the bracket.The dynamic load ore pressure was induced;after the weakening of the coal column blasting,no severe ore pressure appeared,indicating that the weakening of the coal column can effectively avoid the occurrence of dynamic load.Based on the UDEC simulation software,the supporting pressure of the working face in and out of the coal pillars and the weakening of the concentrated coal pillars before and after the weakening of the coal seams were analyzed.The working face was separated by coal pillars,and the interval coal pillars were destroyed.There was no dramatic mining pressure in the mining.Before the weakening of the concentrated coal pillar,the peak value of the supporting stress decreased at the two positions of the coal pillar and the coal pillar at a position of 10 m,which was reduced from 2.9 times of the original rock stress to 1.7 times.The mine pressure appeared to be moderate,and the stress affected area range Reduced from 17?20m to 12?15m.Combined with the actual situation of the site,the prevention and control measures for blasting weakening of concentrated coal pillars are proposed.After weakening,the influence of concentrated stress of coal pillars on mining of lower coal seams is greatly reduced.By monitoring the resistance of the working face over weakened coal pillar support,after the weakened coal pillars are weakened by blasting,the compressive strength of the roof is not high at all stages,and the bracket can meet the production requirements.The research results provide theoretical basis and reference for the safe mining of working face under similar conditions in the mining area.