Understanding tunnel failures during excavation: Causes, limitations, and recommendations

Tunnel excavation failures remain a significant challenge in geotechnical engineering, despite advancements in tunneling processes and risk management frameworks. This article explores the recurring mechanisms of tunnel failures, examines the limitations of current tunneling practices, and presents a methodology to mitigate failures. Drawing on four case histories, the analysis underscores the critical influence of human factors, the incomplete handling of uncertainty, and the limited predictive capacity of existing methods. The article concludes with recommendations to improve robustness in design by integrating ground behavior classification with observed support performance and aligning design and risk analysis with failure mechanisms.