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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in the field of tunnel engineering, where the repercussions of unforeseen circumstances can be catastrophic (Song et al., 2023). In this context, robustness pertains to a system or structure's capacity to endure shocks or disturbances without substantial degradation or total loss of functionality. It involves crafting infrastructures that transcend mere strength, embodying resilience as well. One of the goals of this study is to apply the robustness strategy in terms of: • Risk Assessment • Regular Maintenance and Inspection: carrying out regular maintenance and inspection to ensure that the infrastructure remains in good condition and any potential issues are identified and addressed early • Emergency Response Planning: having a plan in place for responding to emergencies. This could involve having backup systems in place, training staff to handle emergencies, and coordinating with local authorities and emergency services • Continuous Improvement: Learn from past experiences and improve the robustness strategy continuously. This could involve updating the risk assessment as new threats emerge, incorporating new technologies and techniques into the design and maintenance processes, and refining the emergency response plan based on lessons learned (Mobley et al., 2020, Terziovski et al. , 2002) . Applying the robustness concept in this way makes it possible to have infrastructures that are not just capable of withstanding unexpected events, but also capable of quickly recovering and continuing to provide essential services. This holds significance in tunnel engineering, where the repercussions of a tunnel failure can be catastrophic, affecting not only loss of life and property but also causing severe disruption to vital transportation networks. Inverse problems, such as the least squares method proposed by Gauss in 1795, are prevalent in various fields. In bridge structure monitoring, back analysis is used to evaluate the building structure under environmental vibration and strong wind, yielding results close to the measured value (Wells et al., 1971, Tobalina et al., 2020). In underground structures, like tunnels, data processing and extraction of geological data and physical models closest to reality are performed. This process, known as the inversion of information, allows for earthquake prediction in other areas based on local seismic station data. Despite its practical value, inverse analysis is characterized by strong nonlinearity and the need for extensive computation, making it more challenging than forward analysis. In the context of reverse engineering and robustness maintenance strategy, these inverse problems be a method to understand the underlying system or structure by analyzing its output or performance. The insights gained from this analysis can then be used to develop strategies for maintaining the robustness of the system, such as identifying potential weaknesses or areas for improvement. However, the inherent challenges of inverse analysis, such as its nonlinearity and computational demands, must be considered when developing these strategies. 3. Reverse engineering: Mont Blanc tunnel case study This paper describes the application of reverse engineering for the definition of a robust maintenance strategy plan in the Mont Blanc tunnel. The Mont Blanc Tunnel, outstandingly relevant structure, interconnects France and Italy, playing an important crucial role in Europe's strategic connectivity. This motorway tunnel, nestled under Mont Blanc in the Alps, connects Chamonix in Haute Savoie, France, with Courmayeur in Valle d'Aosta, Italy with a length of 11.611 m. It forms an integral part of the European road E25 and significantly reduces the distance from France to Turin and Milan. The tunnel is segmented into approximately 29-meter sections, referred to as "fiches". Thus, the entire length spans from fiche No. 1 (France side) to fiche No. 400 (Italy side). The tunnel, a single bidirectional tube, is one of the main transalpine transport routes. Italy relies heavily on this tunnel, using it to transport up to a third of its goods to Northern Europe. This underlines the importance of the tunnel in facilitating international trade and strengthening economic ties within Europe. The construction of the Mont Blanc Tunnel began in January 1959 on the Italian side and in June 1959 on the French side. The Italian side excavation was completed on August 3, 1962, with the breakthrough of the last diaphragm on August 14 of the same year. The tunnel was inaugurated on July 16, 1965