Analysis on the influence of rocks anisotropy on excavation deformation and seepage of underwater tunnel

Abstract

Taking the Yangtze River crossing section in Wuhu Chengnan tunnel as research background, the coupled hydro-mechanical numerical model was utilized to study the deformation and seepage responses of anisotropic surrounding rocks under the action of tunnel excavation and river seepage. The influences of dominant-developed microcracks inclination, river level, and supporting water pressure on tunnel excavation responses were analyzed. The research result showed that the deformation induced by underwater tunnel excavation was mainly determined by river seepage action. Withdrawal of supporting water pressure would lead to excessive deformation of the surrounding rocks with safety risks, which was more obvious with the increase of river level. The tunnel excavation-induced deformation was also affected by the anisotropic structure of surrounding rocks and supporting water pressure. With the increase of dominant-developed microcracks inclination, the settlement of surrounding rocks in arch roof direction first increased and then decreased. The smaller the microcracks inclination, the greater the water pressure obviously decreased region around the excavated tunnel, as a result larger underwater-ground subsidence scope would be triggered by river seepage action. With the increase of supporting water pressure, the excavated-induced deformation around the tunnel gradually decreased, but excessive supporting water pressure would cause significant ground uplift displacement. It's of importance to select suitable supporting water pressure, but it was influenced by the anisotropic structural characteristic of surrounding rocks.

Keywords

underwater tunnel / rocks anisotropy / hydro-mechanical coupling / numerical computation