Study on combined mining and exploration for the thin coal seams very close under gob water

The 14、16 coal seams in downthrow part of 4 th mining area in Zhao po Mine have been finished its stopping. A lot of gob water stored up in the gob area. This is harmful to the mine of underlying 16、17 coal seams. For this reason, the in situ field examination by special monitoring system and the numerical simulation were carried out. Based on the results of these works, as well as the introducing of point safety degree conception, the developing height of permeable crack zone(especially micro fissures) in overlying rock strata produced by combined mining of 16 17 coal seams and the possible crack depth in the floor produced by combined mining of 12、14 coal seams were studied in this paper. Moreover, the safety of 16、17 coal seams mining very close under gob water was analysed. All of these works will provide scientifie bais for the safe production of Chao po and other similer coal mines.