Reliability Analysis of Shield Tunnel Lining in Service with Field Inspection

Abstract

Under long-term service, shield tunnel linings are prone to diseases such as bolt corrosion, reinforcement corrosion, and cracks; therefore reliability analysis of tunnel linings is significant for overall tunnel stability. This study aimed at developing a reliability analysis method for the bearing capacity of shield tunnel linings in service. Six failure modes of tunnel linings, related to the concrete structure, reinforcement structure, concrete joints, and joint bolts (inner-row bolts and outer-row bolts), are highlighted, and the performance functions of tunnel linings are established according to the failure modes. In this study, the joint structure was treated as a continuous heterogeneous beam in order to simplify the calculation of bolt tension and concrete stress of joints connected with double-row bolts by satisfying the equilibrium of internal force and coordination of deformation. In addition, a field inspection method for lining structure deterioration parameters and a method for calculating the mechanical parameters of deteriorated concrete and reinforcement are elaborated. Because shield tunnel linings suffer from eccentric loads, a Monte Carlo sampling method was used to calculate the probability of a full and partial section compressed condition. The first order reliability method (FORM) (JC method) program was compiled by MATLAB version R2018b to calculate the reliability index of tunnel lining structures; furthermore, sensitivity analysis of random variables was included. The proposed method was verified using inspection data from the Shanghai Dapulu Tunnel. The results showed that the minimum comprehensive reliability index was 2.46 (section 90°) and the maximum comprehensive reliability index was 8.33 (section 40°). The reliability of joint sections was more sensitive to fc, k0, Ab2, γ, whereas structure sections were more sensitive to k0, fy, fc, As, As′, γ.