Analysis and Safety Assessment of Lining Thickness Defects in Highway Tunnels

Abstract

Linings are the main structure of a tunnel to withstand pressure from surrounding rock and their thickness is representative of their load carrying capacity. Tunnel lining thickness defects will have a direct impact on the long-term stability of the tunnel project. Existing research on lining thickness defects focuses on analysis of crown thickness defects using failure load as criteria and is applicable to theoretical research with a lack of guiding significance to actual projects. Based on the test results of lining thickness defects in multiple tunnels of the Liangping-Zhongxian Expressway in Chongqing, this paper covers analyses of thickness defect location and extent and numerical analysis of the effects of different thickness defects on structural performance. The analysis results show: under the same surrounding rock conditions the probability of tunnel lining thickness defects occurring at the hance is similar to at the crown; the probability of thickness defects increases as surrounding rock conditions worsen; when thickness defects exceed 10%, the thickness defect percentage is inversely proportional to the safety factor. The research findings are of practical significance and can provide guidance to NDT, defect treatment and safety assessment.