Analysis of filling effect and filling ratio of backfill mining in longwall face

For studying on the influence of coal pressure appearing and roof break developing height when the working face is mined by backfilling, the key stratum mechanical model of backfill mining in longwall face is established through field mining practice. The minimum backfill thickness has been obtained by theoretical analysis which can ensure key stratum bending subsidence. Then, the overlying strata movement law of backfill mining and fully caving is comparatively analyzed by the numerical simulation system of RFPA. When the longwall face is mined by backfilling, the results showthat the coal pressure appearing is obviously weakened, and the roof fractured zone height is significantly decreased. If there is a fault, mining- induced fractures are also developed through fault zone, and the roof break developing height is approximately equal that of fully caving method.