Study on Safety State of Shield Tunnel under Rotation and Shear Dislocation Deformation Mode

Longitudinal uneven settlement has been noted throughout soft soil areas, which has an adverse effect on tunnel durability. A health degree for longitudinal deformation of shield tunnel structures should be proposed to provide timely judgment and a basis for maintenance departments’ decision-making. A detailed 3D finite element model of the shield tunnel is established. With this model, the relationship between stress of components of shield tunnel structure and longitudinal deformation, composed of the rotation and shear dislocation modes simultaneously, is explored. A strong positive correlation between the longitudinal deformation and the stress of longitudinal bolt and segment is found. Based on this relationship, a health degree of longitudinal deformation of shield tunnels is proposed, which is partially proved by the limit value of the Chinese standards. In comparison with the standards, more deformation form can be considered, which is more practical in the field.