Time-dependent reliability method for service life prediction of reinforced concrete shield metro tunnels

Ageing and deterioration of underground tunnels is inevitable after their long-time in service. This necessitates a rigorous assessment of the probability of failure due to deterioration with a view to predicting remaining safe life. In the light of considerable research undertaken on prediction of service life of the aboveground structures, e.g. bridges, few such studies dealing with the underground structures, e.g. tunnels, have been carried out. The intention of this paper is to present a time-dependent reliability method to assess the tunnel probability failure due to different mechanisms of deterioration. Stochastic models are developed for four common failure modes of tunnel structures as identified by strength and serviceability criteria. Application of the proposed methodology is demonstrated in a case study. It is found in the paper that the reinforcement corrosion is a key factor that affects the probability of deterioration failure and that all deterioration scenarios need to be considered in the assessment of tunnel failures and prediction of their remaining safe life. The proposed method can help the asset managers and practitioners in developing rehabilitation or replacement strategy for existing tunnels with a view for better management of the valuable tunnel asset.