Study on the Water Burst Characteristics and Risk Aversion in Water-enriched Karst Tunnel with High Hydraulic Pressure

According to the statistics and phenomenon analysis of water bursts occurred in Maluqing Tunnel of Yiwan Railway, the characteristic and the mechanism of water burst disaster occurring in water-enriched karst tunnel with high hydraulic pressure is summarized. Before the water burst occurs, dissolve gap and vascular are expanded to confluence by water pressure and the surrounding underground water is taken over. When water storage and cavity static pressure reach the critical values, the blockage layer at the bottom of the cavern will be broken through and water burst will occur instantaneously. By analyzing the observation results of rainfall, water inflow, water seepage test and water level, the water inflow is predicted by the rainfall infiltration method and statistics analysis method respectively and the key parameters of risk control, such as water storage volume of cavern, accumulation rate and mechanical properties of sedimentation and thickness of the confined bedrock are also presented. In addition, some quantitative indicators of secure access to the tunnel are obtained.