Numerical simulation on mining process of steep inclined and long distance protective seam and site application

Base on the UDEC3.1 software of the computer system,the paper simulated and analyzed the crack evolution law of the overlying strata during the mining in No.K93 seam as the underneath protective seam.The simulation results showed that the No.K93 seam have the validity as the protective seam.Finally with the site effect investigation,the gas pressure of No.K7a seam and the borehole gas emission variation law before and after the mining of No.93 seam were obtained.