PSI - Issue 62

Salvatore Aiello et al. / Procedia Structural Integrity 62 (2024) 1128–1136 S. Aiello et al./ Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Social development has led to the adoption of high standards for tunnels. Nevertheless, disasters can occur during operational lifespan of mountain tunnels due to high geostress, temperature, hydraulic pressure or special adverse layers. Mont Blanc Tunnel fire in 1999 is a prime example of a tunnel accident that resulted in 39 fatalities, (Lacroix e al., 2001). More recently, the Gottardo tunnel in Switzerland was closed due to a 25-meter crack found in the tunnel’s vault. These incidents underscore the importance of regular maintenance and safety checks in tunnel networks. Against this backdrop, the development of efficient systems for maintaining and investigating on the structural condition of infrastructure is crucial for implementing economically sustainable maintenance plans that ensure a high level of safety (Frangopol et al., 2019, Xue et al., 2023). Furthermore, it is essential to devise new strategies to enhance the effectiveness of these systems in the long run. After the 2019 collapse event in the Berté tunnel (A26) in Italy, the Ministry of Infrastructure and Transport initiated a comprehensive inspection of all motorway concessionaire tunnels. In 2022, the Guidelines for the classification and management of risk, safety assessment, and monitoring of existing tunnels were officially sanctioned. The structure of these Guidelines is designed to enhance and organize knowledge pertaining to managed infrastructure. This knowledge is categorized into distinct levels and areas, employing a multi approach level, with the primary objective of identifying priority classes in relation to the recognized potential dangers. Innovation plays a significant role in the evolution of tunnel maintenance. As the demand for underground infrastructure increases globally, the tunneling world is innovating to ensure security, speed, and performance. Automation, robotics, artificial intelligence, and data analysis techniques are being employed to enable faster, more consistent, safer, and eco-friendly drilling. These advancements not only improve the state of the art in high-end, high-accuracy applications but also open new low-end use (Rosso et al., 2023, Marasco et al., 2022, Chiaia et al., 2022, Aiello et al., 2023). The integration of reverse engineering into maintenance robustness strategies is a promising innovation. Reverse engineering enables us to delve deeper than what is immediately apparent, uncovering hidden structures and revealing both the design and potential improvements of an object or idea. The application of reverse engineering to define a robustness strategy for maintenance is a promising development. Reverse engineering allows one to look beyond what is evident on the surface and find a hidden structure, revealing both how an object or idea was designed and how it can be improved (Friedman et al., 2021). In the context of tunnel maintenance, reverse engineering can be used to understand the factors affecting maintenance budget allocation, estimate some characteristics unknown for the age of the structure, identify any structural problems or identify areas for improvement to increase safety. This study demonstrates the use of a methodology that employs reverse engineering to establish threshold values for the resistance of the Mont Blanc tunnel’s concrete lining . This is done with the aim of creating a potential monitoring system and fostering collaboration with the findings of various inspection campaigns. This is achieved by generating summary tables that contribute to the development of a robust system for monitoring and maintenance. 2. Reverse engineering and robustness strategy concepts The concept of reverse engineering, traditionally associated with the replication of existing designs, could find a novel application in the world of civil infrastructure engineering, specifically in tunnel construction and maintenance. The definition of this practice involves “taking apart” and analyzing a physical object point by point to understand how it was designed, a method traditionally used for replicating products. Nowadays, this technique proves invaluable in scenarios with limited knowledge about a structure's engineering, or when original documentation or 2D/3D drawings/CAD models are not accessible (Friedman et al., 2021). This scenario frequently arises during the development of management and maintenance plans or structural designs, particularly for constructions predating the 1980s, as is often observed within Italy's infrastructure network. The robustness strategy is a forward-thinking approach that underscores the necessity of creating infrastructures that can withstand unexpected events without leading to disastrous outcomes. This strategy is particularly pertinent