Surface subsidence prediction for the WUTONG mine using a 3-D finite difference method

WUTONG coal mine is adjacent to an auxiliary dam of the Yuecheng Reservoir. In this paper, mining-induced surface subsidence prediction is conducted by means of the finite difference method (FDM) to judge whether the extraction of the coal seam will have a negative impact on the dam. First, the initial values of the rock mass mechanical parameters are estimated using the available literature that relates intact rock and discontinuity properties to rock mass parameters. Then, based on available surface subsidence monitoring data on WUTONG's mined areas, the main mechanical parameters of coal and rock masses are determined by a back analysis procedure that combines an experimental design technique with numerical simulations. Finally, the surface subsidence results in the mining area are numerically predicted for four different mining scenarios (S1 through S4). Scenario S3 emerged as the best choice of these four scenarios. The predictions are: (1) the maximum surface subsidence within the mining area is 2.14 m, with the maximum settlement point located in the mid-west area of the coalfield, and (2) the nearest distance from the boundary of the surface movement area to the edge of the dam foundation is 35 m. Therefore, mining the coal seam will not cause damage to the dam.