Abstract：With respect to the disasters caused by leakage when Huanshanping tunnel passes through a shallow with rich groundwater or other fault zones，combing with the observing results of NATM monitoring，the mechanical mechanism caused by groundwater in a complex geological condition is analyzed，the measurements for leakage proof and reinforcement adopted in construction process is introduced，and the engineering experience in large-span tunnel construction is briefly summarized. It is believed that the research has reference to the prevention for disasters in tunnel construction under poor geological condition.
