The construction of Daxiang mountain tunnel in water-rich fault has great risks of causing water bursting and mud gushing easily. High-position drainage can reduce water pressure ahead of working face effectively. By using field test and numerical simulation

under different water-level conditions

the interrelation between method of high-position drainage and stability of tunnel is studied; and the optimal plan of arrangement of high-position drainage pipes is put forward. Studies show that: maximum water pressure of Daxiang mountain tunnel in fault is up to 1.98 MPa. The tunnel can be constructed securely after drainage and the maximum water head is only 10 meters. Therefore

prevention of water bursting is mainly concentrated in the period of tunnel face excavation. The drain volume of drain pipes at vault is maximum. The closer drain pipes and arch foot are

the more poor drainage capacity is; and the density of drain pipes at vault should be higher than that at arch foot. In actual construction

for faster to reach drain effect

drain pipes at vault should be first to arranged

then at arch foot. Interrelation between number of drain pipes

drain volume and extrusion deformation of tunnel face is studied. According to economy and effect of hydrophobic reinforcement

reasonable drainage scheme is put forward.