Abstract:

In order to study hydrogeological parameters of unconsolidated confined aquifer of North China type coal field and its significance to groundwater numerical simulation, the fourth aquifer of the Quarternary (4th aquifer) in Qidong coal mine, Sunan mining area, Huaibei coal field, Anhui Province, is studied as an example. Based on the hierarchical analysis-fuzzy comprehensive analysis method, the study area is divided into ten divisions under hydrogeological parameters of 4th aquifer. The hydrogeological parameters of each division are properly determined, which are used for dynamic numerical simulation of groundwater flow under mining circumstances. The results of numerical simulation show that the variation of groundwater flow field is unconspicuous in the process of mining of shallow coal seam from 2008 to 2012 in Qidong coal mine, but the differences of groundwater level between the north and the south increases year by year; therefore, groundwater always flows from the south to the north, which hydraulic gradient decreases in the north and increases in the south gradually. The results also show that the decrease zone and the increase zone of hydraulic gradients are separated by the Weimao fault with a dip of 60-70 degree and a slip of 10-320 meters. It is concluded that a fault with great dip and slip in the bedrock are keys to hydraulic gradient anomaly in the overlying unconsolidated confined aquifer.

Key words: unconsolidated confined aquifer, hydrogeological parameter, groundwater flow field, numericalsimulation