Effect of Water on Tunnel Face and Surrounding Rock Deformation: Fid-Bau Portal

Effect of Water on Tunnel Face and Surrounding Rock Deformation

An, Yonglin / Zhou, Jin / Hu, Wenxuan / Li, Jiahao

To keep construction safe in water-rich stratum is one of the most challenging problems faced by tunnel designers and constructors. In this paper, the Shuiqing Tunnel, as for the engineering background, is located in Bijie-Zhenxiong Highway, Guizhou Province, China. The New Austria Tunneling Method is adopted. The inner diameter of the tunnel is 10.86 m, and the bench width is 4.5 m. The failure shape under different saturation time is firstly studied through laboratory-experiments. And mass fractal dimension formula is derived by calculation of the mass percentage of each particle size after failure. Simulations of different water level on the tunnel face and surrounding rock deformation are established. Finally, the transient seepage in groundwater is discussed from different paths. Results show that, with the increase in immersion time from 0 to 10 day, the average mass fractal dimension of rock sample increases from 1.91 to 2.21. When the samples are dry and saturated for two days, the failure modes are mostly single shear failure, and the main crack is longer. However, when the samples are saturated for six or ten days, the failure modes are splitting failure with more cracks, and the rock samples are fragmented into many small pieces.When the water level is higher, the surface settlement, the deformation of the face and the damage of the surrounding rock are larger. The lower the water level, the larger the influence range of the negative pore water pressure, and the main affected area is about 2 m below tunnel face. With the increase in seepage time from 0 to 50 s, the pore water pressure decreases gradually; After 50 s, the pore water pressure almost keeps constant, meaning the hydrostatic equilibrium is reached again.