Abstract: The water and sand gushing accidents occur frequently in shield tunnels located at confined aquifer of soft soil areas in China, resulting in huge economic losses and adverse effects. However, due to the high water pressure in the confined aquifer, it is difficult for the traditional methods(e.g., grouting technique) quickly playing an effective role. According to the settlement-time curve after the seepage disaster, the development process of the disaster is put forward. Based on the rapid construction of wells in 6-8 hours, which is proved in field tests, an emergency plan of rapid decompression and recharge of confined aquifer is suggested during the slow development period of seepage disaster in the shield tunnel. The feasibility of applying this technology in tunnel emergency rescue is analyzed by using the precipitation theory considering the water level in the well. The results show that this technology can reduce the water level at leakage point in a short time and thus can control the surrounding water level at the same time. The shorter time to deal with the tunnel disaster requires, the higher amounts of pumping and recharging water require. When the ratio of distance between pumping well and recharging well to the leakage point is fixed, the smaller the distance value is, the fewer pumping and recharging water amount require. The circumferential buildings can be protected by arranging the recharge wells along the ring using the decompression center as the center of a circle. Finally, the design steps and well layout principles of emergency rescue (i.e., decreasing the pore pressure in the confined aquifers) are put forward.

Key words: tunnel leakage, emergency rescue, recharge, rapid decompression