Research on Mining Fracture of Overburden in Close Distance Multi-seam

In order to explore the influence of the mining fracture of the lower coal seam mining to the previous upper coal seam mined in close distance coal seams, the shallow multi-seam of XinLiangyou mine in county Pu of Shanxi Province is selected as study field to establish a numerical model of multi-seam mining in close distance coal seams with RFPA2D. The failure of overburden as well as the rule for development and redevelopment of fracture is studied and the change rule of vertical stress for workface is also analyzed. The results indicate that: the lower coal mining can lead to the redevelopment of mining fracture and increase the height of previous upper coal mined, which belong to the close distance coal seams; Repeated mining can cause the decrease of vertical stress concentration coefficient for mining field. Finally, the results which result in affecting aquifer even surface water are consistent with the observation.