Research database

The recent release of the Guidelines for the risk assessment and classification of existing tunnel linings has posed a significant challenge for the Highway Managing Societies. These organizations are required to classify the several single risks and the global risk associated with each tunnel lining, necessitating a huge number of in-situ inspections and surveys. This data is crucial for designing and organizing temporary or definitive retrofit and strengthening interventions. Following the guidelines' recommendations, the initial focus should be on tunnel linings built in the 60s, typically casted in place and lacking waterproofing layer. The first objective of the project is to critically assess the guidelines and determine their applicability to pre-cast tunnel linings. The second aspect involves evaluating the risk variation resulting from temporary interventions. Indeed, these temporary interventions, which typically have a validity of about three years, are implemented in response to potential hazards identified during in-situ inspections, especially in the external concrete layer. The mentioned interventions are not specifically tailored based on a reliable understanding of the specific situation. Instead, they often involve the adoption of repetitive general schemes. However, while these temporary interventions mitigate the structural risk, the presence of construction works in the tunnel increases the probability of traffic accidents. The second objective is to propose a method for assessing the structural and geotechnical risks of tunnel linings, providing a more reliable decision-making procedure to evaluate the convenience of performing temporary strengthening interventions. Finally, the last two objectives are associated to delineating strengthening interventions for damaged tunnel linings.