Probabilistic Assessment for Concrete Spalling in Tunnel Structures

Abstract

Concrete spalling in prefabricated shield tunnels is a well-recognized issue in underground engineering that impacts the performance and reliability of a tunnel. This paper presents a novel multivariate probabilistic assessment methodology to estimate failure risk, damage growth, and residual useful life of a tunnel structure in terms of its concrete spalling, with the ultimate purpose of facilitating predictive maintenance for prefabricated shield tunnel structures. The multivariate hierarchical approach, a proportional hazard modeling technique, is developed to model the spalling accumulation in a given tunnel segment. The probabilistic model is developed from historically inspected data and characterized to take into account various influencing factors. The most broadly used lognormal distribution is investigated in the development of probabilistic damage accumulation modeling for concrete spalling, with its distribution parameters modeled as a multivariate function of multiple influencing factors. A generic procedure combining multiple qualitative and quantitative techniques is proposed to systematically verify and validate the probabilistic model, considering uncertainties. Advanced lifing analysis approaches, including conditional risk estimation, spalling growth projection, and residual life estimation, are derived from the established empirical model. The probabilistic methodology associated with statistical data analysis techniques is demonstrated by using the spalling data collected from real-world subway tunnels.