Abstract: Numerical model for coal seam group mining in Wanli mining area was built by using the software UDEC, the process of the fractures development and the interaction when mining between the coal seams group were numerically studied, the development rules of the failure of the overlying rock mass was analyzed and its predicting height of 3-1 coal seam determined. The numerical simulation results shows, 5-1 coal seam mining process caused the slightly increased of the overburden fracture height of 3-1 coal seam, and the height of water flowing fractured zone of 3-1 coal seam can reach 40 m. Moreover the height predicted by empirical formula is 41~50 m, and the height measured by transient electromagnetic and drilling is 45 m. Based on the development rules of the failure of the overlying rock mass, the mining area is divided into 5 kinds according to water-rich degree of aquifer and the thickness of water-resistant strata, namely, non water area, non water protection area, natural water protection area, water protection area and observation area. According to water protection area, we put forward a set of water protection techniques, which is applicable for mining practice.

Key words: fracture of overburden, water flowing fractured zone, UDEC numerical simulation, aquifer-protective mining