Numerical Simulation on Height of Water Flowing Fractured Zone Development in Overlying Rocks Under Hard Roof Coal Seam Group Mining

Numerical model for coal seam group mining in Datong Mining Area was built by using the software FLAC^3D, the fractures development during mining process in coal seam group were numerically studied, the development laws of the failures with thickness and face length of 3-5^# coal seam was analyzed. The results show that, with the increase of coal seam mining, the increase of fracture development trend declined; the height of fracture increases with the increasing of thickness of 3-5^# coal seam; when the coal thickness is greater than 13 m, the fracture height increases quickly; the height of fracture zone increases the face length. When the face length is larger than 190 m, the increase of fracture development trend declined; when the coal thickness is 15 m, the working surface length shortened to 180 m, which can make sure that the fracture zone of 3-5^# coal seam and the goaf of 15^# coal seam are not related.