Seismic damage characteristics of large-diameter shield tunnel lining under extreme-intensity earthquake

This paper investigates the damage pattern of the concrete lining in a large-diameter subsea shield tunnel under different seismic loading intensities. Based on the Shantou Bay (STB) Tunnel, a refined finite element (FE) model consisting of "1/2 + 1+1/2" liner-rings is established in the study. In addition, another FE model considering both the strata and lining is created to obtain the seismic displacement-time history, which is employed as the boundary conditions on the "1/2 + 1+1/2" liner-rings model. A whole-ring model is thereafter generated considering the segment details, adopting the Concrete Damage Plastic (CDP) constitutive assumption and artificial viscoelastic boundary. An improved reaction-displacement method based on the concept of the "equivalent layer" is proposed to consider stratum-structure interaction. Finally, two types of seismic intensities and three work conditions are employed to investigate the influence on lining segments and joint openings. The results show that: (i) the damage to the segment of the shield tunnel is mainly concentrated in the top and bottom of the arch and the outer area of the waist under seismic loading; (ii) the moment of a sudden change in the damage development trend and the joint opening is related to the peak response of seismic time history; (iii) the segments of the shield tunnel are dominated by vertical oval shape deformation under a horizontal earthquake, and dominated by horizontal oval shape deformation under a vertical earthquake; (iv) the area and level of lining damage increase with the development of the earthquake intensity.