Study On The Law Of Ore Pressure Display In Stope Under Close Overlying Coal Pillar In Yanzishan Mine

In our country,the well coal mine generally adopts the method of keeping coal pillar long wall mining,which leaves a lot of residual coal pillars in gob,which brings strong mining pressure safety influence in the lower coal mining face.Taking the 8212 working face of C3 coal seam in Yanzishan Mine of Jinneng Holding Group as the research background,combined with the occurrence characteristics and mining conditions of the main coal seam,this thesis studied the mining pressure developing law of stope under the overlying and inclined coal pillar by using the methods of theoretical analysis,numerical simulation,physical simulation of similar materials and field engineering measurement.The corresponding prevention and control measures are proposed according to the site engineering.The main research results are as follows:(1)According to the progressive failure theory analysis of coal pillar,it can be concluded that the remaining strike coal pillar on the 8212 working face of C3 coal seam will not have instability failure before being affected by the mining of the lower coal seam working face.The stress distribution characteristics of coal pillar under concentrated load and uniform load are analyzed by using the theory of elasticity.(2)The influence of overlying strike coal pillar with different widths on 8212 working face of C3 coal seam is analyzed by numerical simulation.The results show that when the width of the coal pillar increases from 30 m to 60 m,the vertical stress on both sides of the coal pillar decreases by 7.5%-12.5%,the vertical stress in the middle of the coal pillar decreases by 40%-50%,and the stress concentration coefficient of floor strata decreases by 35%.8212 working face is affected by the superposition of leading stress and concentrated stress of coal pillar,and the peak value of supporting stress of working face reaches 42 MPa.The larger the width of overlying coal pillar is,the greater the affected range of supporting stress of working face is along the tendency,but it decreases along the strike.(3)The physical simulation studies the overburden migration,fracture evolution and ore pressure development of the lower coal seam working face overburden the remaining inclined coal pillar under the condition of different layer spacing.The results show that,under the condition of small interval between layers,the mining-induced fractures of interlayer rock mass develop abnormally when the working face leaves the boundary of overlying coal pillar,and the roof strata are prone to shear roof slip,leading to the appearance of strong ore pressure and even the buckling of working face.The overlying coal pillar has little influence on the mining of the lower coal seam working face under the condition of large spacing between layers.The greater the interval between layers,the weaker the influence of coal pillar on the abutment pressure,but the wider the influence range.(4)In view of the coal pillar left over from No.4 coal seam on the 8212 working face of No.C3 coal seam,ZF1200/23/35 D type normal four-rod low top coal support is selected as the working face support.When the coal pillar of No.14-2 and No.14-3coal seam is overlying the 8212 working face,it is suggested to reinforce the support in advance,speed up the promotion speed,and push out the coal pillar covered area as soon as possible.There are 87 figures,6 tables and 92 references in this thesis.