Numerical simulation of head top coal's stability control of fully mechanized longwall mining with sublevel caving face in large dip seam

Stability control of the head face's top-coal is one of the key techniques of realizing high production and high efficiency to coal mining in fully mechanized top-coal caving face. The characteristics of the stress in the overlying strata of the fully mechanized top-coal caving face and the top coal were analyzed using FLAC3D. The destroyed law of the tip-to-face top-coal and its characteristic of the displacement were analyzed. The results show that the tip-to-face top-coal generates the large deformation while it is in the stress-relaxed area. The top-coal in the front of the wall appears the failure area in the effect of the abutment pressure that spreads over the coal seam. The surrounding rock of the upper face end is the key part strengthened the control of the rib spalling. The first and frequent appeared phenomenon of losing stability of the powered supports is that the back base of the hydraulic power supports in the upper of the face slips. Supporting in time, increasing the quality of support and so on can keep the stability of surrounding rock.