Statistical interpretation of tunnel project characteristics and their influence on technical risks – current and future challenges

Tunnels are an increasingly significant part of our built infrastructure. Simultaneously, they are subject to a diversity of inherent uncertainties associated with the geotechnical, hydro-geological, and physical environment surrounding them. The associated risks can materialize on many occasions, leading to disasters with substantially high reinstatement costs, incurred delays, and damage to adjacent third-party assets and the environment. Such disasters can occur due to extreme natural events and unforeseen and unforeseeable ground conditions or accidents. but also, human-driven issues, such as substandard design, poor project management, aggressive project timelines leading to safety shortcuts, compressed budgets and application of innovative techniques not yet fully tested and validated, are some factors contributing to an increased probability of risk materialization and disastrous events. This paper aims to provide a statistical interpretation of tunnel project characteristics and their influence on technical risks based on a database with approximately 400 tunnel failure cases. A further goal of the study is to support decision-makers in the risk management process, such as owners, engineers, and insurers by improving their understanding of project sensitivities. The results indicate the significance of technical characteristics (such as tunnel
dimensions, construction type, and ground formations). Still, they also reveal some dependence between lower project risks and the application of current project and risk management practices.