Numerical simulation and control technology of fracture characteristics of lower strata in gob-side entry retaining

In order to solve the problem that the stability of main roof and gob-side entry retaining ( GER) was seriously affected by soft and broken immediate roof, UDEC Trigon model, based on No.3414 mining face of Xinyuan Coal Mine, was established to simulate the fracture characteristics of lower strata in GER under differen t support conditions and the effect on the stability of the surrounding rock of GER was analyzed. The results showed that the fracture in the surrounding rock of GER wa s mainly composed of shear cracks, and tensions cracks were more in the roof of flling area which was the weak link in the control of surrounding rock in GER. When t he lower strata broke outside the backfilled body, the development of the shear cracks in coal rib was inhibited and the stability of the load-bearing structure make up of backfilled body and coal rib was increased. The engineering practice showed that the lower strata broke outside the backlilled body, the convergence between roof and floor was 900 mm, and the convergence between ribs was 800 mm, which was appropriate to ventilation and gas emissions, after the adoption of high prestressed and high rigidity anchor cable in the roof of flling area.