Study on Coal and Rock Pressure Releasing Effect of Protected Seam Mining Under Long Distance

Abstract：Based on the overburden strata movement and failure features of the protected seam mining,the paper had an analysis on the feasibility of the coal and rock pressure releasing in the protected seam mining under long distance.The FLAC2D numerical simulation software was applied to the study on the stress distribution features of the protected seam,seam thickness variation law,the horizontal displacement law,the pressure releasing scope and the pressure releasing angle.The results showed that during the underneath protective seam mining,the height of the crack zone was developed to the protected seam,swelling deformations were occurred in the seam,great secondary cracks were occurred and thus different pressure releasing were occurred in the protected seam.Meanwhile,the horizontal displacement occurred would be favorable to improve the permeability of the seam.On the strike direction,the protected seam was moved about 30 m to the direction of the goaf of the protective seam.The protected seam was in the stable swelling deformation zone and the effective pressure releasing angle in the strike was about 66°.After the study results applied to the practical projects,the gas pressure of No.13-1 seam in a mine of Huainan was reduced from previous 4.4 MPa to 0.7 MPa after the seam pressure release,the permeability coefficient of the seam was increased by 1 061 times.Thus the method would be a good regional outburst prevention measure.