Abstract：ater-break phenomena occur in some wells in Bajiazi Village，Fuxin Coalfield because of coal mining. The conditions of this case are employed. The hydrogeology qualitative analysis on the groundwater loss mechanism induced by underground mining is carried out. Then numerical simulation is performed with the rock failure process analysis (RFPA2D) code. The change and redistribution of the stress field of the rocks around the stope are studied，and the process from initiation，propagation，and coalescence to rupture of rock crannies around the stope is reproduced. The process shows the transformation and adjustability of the groundwater seepage action and the course of the groundwater leakage to the goaf through the crack. The results of numerical stimulation are consistent with the result of the hydrogeology qualitative analysis，which proves that REPA2D is one of the credible numerical quantitative analysis method to forecast the cranny¢s initiation，propagation，and other hazards(such as the groundwater runoff in this paper). The results of numerical stimulation show that although the goaf and influenced area are in different hydrogeological unit，the groundwater seepage channels are influenced by mining，which provide a favorable hydrogeological condition for the water runoff and accumulation to deep goaf，and make the stope that originally do not possess leakage conditions into a reservoir that can take up prodigious seepage.
