Numerical study on transverse deformation characteristics of shield tunnel subject to local soil loosening

Abstract

In this study, a refined numerical model for segmental lining of a shield tunnel, which contains detailed models of reinforcement and connecting bolts, is established using finite element software. The model is first validated by the results from a full-scale model test. Then, based on the load-structure method, this numerical model is adopted to investigate the internal force distribution and the transverse deformation characteristics of the shield tunnel when it is subject to local soil loosening. The influence of loosening position, loosening range, and loosening extent on the mechanical response is extensively studied through comprehensive numerical analyses. The results show that the main influence of local soil loosening on the ring is to disturb the force balance and change the constraint conditions, thus changing the deformation pattern and force state. After the loosening occurs, the bending moment of the ring in the loosening range increases and the axial force decreases. The vertical convergence of the ring is the largest and the equivalent stiffness of the ring is the smallest when the local soil loosened at the haunch and the loosening range α is 90°. The vertical convergence of the ring increases with increasing of the loosening extent, and the equivalent stiffness decreases linearly with increasing of the loosening extent. The results can enhance our understanding of mechanical behaviors of segmental lining associated soil loosening, and will show a possible way for detecting soil loosening based on the measured deformation and internal forces.