Abstract: To study the surrounding rock stability of deep buried water-rich tunnel in the presence of seepage, we conducted numerical simulation of the excavation process of a tunnel project in FLAC^3D in consideration of fluid-solid coupling, and further compared the simulation result with field monitoring result. The comparison revealed that the gradient of pore water pressure changed rapidly after the left bottom sidestep was excavated, indicating that water burst would probably occur at both sides along with tunnel excavation; the stress and pore water pressure tended to be stable after the excavation of inverted arch. Furthermore, we proposed an excavation risk function according to α, which is defined as the ratio of pore water pressure to stress, to determine the most dangerous depth of working face excavation. When α is larger than 4.51, the working face is extremely prone to suffer from instability, indicating that drainage is required. The predicative function is of high accuracy, hence could offer reference for future projects.

Key words: tunneling engineering, fluid-solid coupling, inversion theory, field monitoring, numerical simulation, prediction function