Ground settlement and fault deformation response to deep-buried tunnel excavation and groundwater drawdown

Abstract

The groundwater drawdown caused by tunnel excavation may induce large-scale deformation, including uneven settlement deformation of rock mass and local deformation of faults, which poses a great risk to engineering safety, and requires the constraint of deformation stability. Based on the theory of deformation reinforcement and the effective stress principle, we study the nonuniform deformation and unbalanced force distribution of the rock mass and faults caused by the groundwater drawdown after the excavation and drainage of the deep tunnel. The results suggest that the groundwater level drawdown can increase the effective stress in a wide range, and significantly disturb the stress and deformation of the rock mass. It is noted that the fault crossing the tunnel is relatively dangerous under these disturbances, and deserves special attention. Moreover, the unbalanced force and the plastic zone can be transmitted to further distances along the fault, and reinforcement and support should be carried out in time. In addition, the greater the Biot coefficient can lead to the greater impact of groundwater drawdown on stress changes and deformation of the rock mass and faults.