Abstract: Five water inrush events happened in Liangbei coal mine. The water source was from the confined Cambrian karst aquifer under the coal seam. According to the hydrogeological conditions of Liangbei coal mine, the numerical models, including non-fault and fault models, were established with FLAC package. Based on the theory of rock mechanics and seepage mechanics,numerical simulations were directed for revealing the failure evolution of the seam floor above the high pressure confined aquifer.Different fault factors such as fault depth and location controlling the failure of coal seam floor were discussed. Simulation results showed that failure depth for the fault model increased 20%-33% compared to the non-fault model. The fault zone, especially the area of 10 meters ahead of the fault to 15 meters behind the fault, must be paid more attention to. Accordingly, the grouting reinforced projects were designed for No. 11041, 11151, 11111 working faces in Liangbei coal mine. Targeting the failure zones of coal seam floor and fractures on top of the confined Cambrian karst aquifer, the grouting projects reinforced the water-resisting strength of the coal seam floor, which assured the safe mining in Liangbei coal mine.