Numerical simulation research on mining stress field of overlying coal-rock seam under far distance lower protective seam mining

In order to research the problem that mining underlying No.8 coal seam can alleviate strong strata behavior during mining No.3 coal seam or not, a far distance lower protective seam mining scheme was simulated by use of FLAC3D software, and stress peak value, stress distribution and plastic range were analyzed during mining process of the protected No.3 coal seam before and after mining the lower protective No.8 coal seam. The research results show that with the lower protective No.8 coal seam advancing, inclined stress of working face of the protected No.3 coal seam represents "M" shape, namely both ends of coal body shows stress concentration, and stress in middle region is lower, so as to make surrounding rock of the No. 3 coal seam working face roadway, which is arranged in central pressure relief area, get pressure relief with different degree. After mining the lower protective No.8 coal seam, the stress peak value of the protected No.3 coal seam working face is reduced about 18%, and mining influence distance is shorted about 10 m. Meanwhile, stress concentration degree is weakened, and new plastic zone does not appear in coal body of the working face.