Study on Pillar Stability of Wongawilli Mining Area in Shallow Close Distance Coal Seams

In order to ensure the lower working face safety production under Wongawilli mining area pillars in shallow close distance coal seams in Bulianta coalmine, the influence of Wongawilli coal pillars’ stability in upper coal seam on lower working face is studied by three-dimensional simulation and field measurement. The results of finite element software FLAC3D shows that, the maximal vertical stress in Wongawilli coal pillars is 32 MPa, and the stress concentration factor is 4.8, but the pillars in Wongawilli mining area are stable. The results of on-site surface subsidence and rock pressure appearance shows that, the surface subsidence value corresponding to Wongawilli coal pillars is much less than old gob area, and the rock pressure appearance of mining face is always normal, so the result indicates that Wongawilli coal pillars are not unstable and the safety of extraction of 32301 working face is ensured. The research achievement would provide technique support for safety mining under similar condition in Shendong mining district.