Characterization of Crack and Leakage Defects of Concrete Linings of Road Tunnels in China

Abstract

This paper presents a comprehensive statistical study on crack and leakage defects of road tunnel linings in China with newly proposed quantitative indexes that can be easily evaluated by robotic inspection techniques. These indexes are crack density, average crack length, nominal crack width, leakage density, and leakage state index. A database covering the defects of 116 road tunnels in China is built from on-site inspection and literatures. Key factors for each evaluation index are determined by analysis of variance and partial correlation analysis. Nonstructural crack is found to be the dominant type of cracking. Temperature-shrinkage stress is the main reason for cracking in cold-region tunnels. Seepage is the most common type of leakage. The underground water source plays a crucial role in the formation of leakage. Probabilistic modeling of the defect is carefully investigated: crack density and leakage state index can approximately follow normal distribution. Leakage density and average crack length are lognormally distributed, whereas nominal crack width of composite-lined new tunnels follows exponential distribution. Bayesian updating is carried out for nonparametric estimation in the case in which the conventional maximum likelihood method is not applicable due to data deficiency. The proposed probabilistic models are validated by on-site inspection and theoretical checking computation.