Abstract: According to the engineering geological and hydrogeological conditions of fault F field of a tunnel project, we analyzed the fault’s hydrogeological characteristics by determining the permeability coefficient through deep pumping, pressure test as well as recovery test. On this basis, we built a nonholonomic computation model of a horizontal underwater gallery which is in infinite water body. Furthermore, we calculated and analysed the dewatering result of four schemes (three different schemes of drainage hole layout and a well-point dewatering scheme). Finally, we compared the theoretical calculation results and concluded that the drainage hole arranged at both sides could effectively reduce the water level and meet the design requirements. Practice verified the feasibility of the dewatering scheme. It provides reference for similar tunnel projects.

Key words: tunneling engineering, fault belt, dewatering and depressurization, well point superposition method