PSI - Issue 62

Ettore De La Grennelais et al. / Procedia Structural Integrity 62 (2024) 1089–1096 Tobia Zordan/ Structural Integrity Procedia 00 (2019) 000 – 000

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To accurately document the observed conditions, it is essential to complete the "initial inspection sheet" and "defect sheets" in accordance with the Level 1 guidelines. In case certain areas are inaccessible by conventional means due to structural or covering obstacles (such as cladding, lighting systems, or electrical installations), the criticality is identified, and a strategy is agreed upon to address the issue, ensuring a comprehensive and systematic approach to tunnel management. A photographic summary of a Level 1 inspection activity along with an example of the corresponding inspection sheet are shown in Fig.4 and Fig.5. In this sheet, the specific code related to a particular defect is associated with its position relative to the road axis and its position in the cross-section of the inspected section. As per the Guidelines methodology, each defect (identified by a specific code) is associated with an index indicating the extent and severity of the defect. 5. Determination of attention class - level 2 In accordance with the new Guidelines, Level 2 requires the definition of an Attention Class (CdA) for each examined tunnel. This class is determined based on factors such as hazard, vulnerability, and exposure, subdividing into categories of high, medium-high, medium-low, and low risk, considering the route under worst conditions and qualifying the tunnel based on specific types of potential danger. Each attention class involves specific actions, such as investigations, monitoring, and checks, adapted in relation to the diffusion index and any characteristics. This is achieved with logical operators contained within the Guidelines themselves. In particular: • For tunnels classified with a High Attention Class, it is mandatory to promptly initiate thorough assessments, including safety analyses and investigations related to hydraulic, geological, geotechnical, structural, and road characteristics, based on the specific Attention Class and the type of associated potential risk. For tunnels classified with a High Attention Class, it is also necessary to conduct in-depth inspections with possible installation of monitoring systems. • For tunnels classified with a Medium-High Attention Class, ordinary and in-depth inspections are planned. Specialized investigations will be carried out, and if necessary, monitoring systems will be installed. Based on inspections, preliminary Level 3 safety assessments will be conducted with possible in-depth assessments. • For tunnels classified with a Medium-Low and Low Attention Class, periodic inspections are planned, as specified in the dedicated section of the guidelines. However, regular in-depth inspections are also foreseen, evaluating the confirmation of the Attention Class and the need to initiate preliminary safety assessments. 6. Case study of Comelico Tunnel The Comelico Tunnel, situated in Auronzo di Cadore, Italy, spans a length of 4 kilometers and is slated for structural consolidation and plant renewal. Numerous segments of the tunnel, marked by a notably elevated level of defects, are presently shielded from direct view, concealed behind protective panels. Pending these works, an investigation campaign on the tunnel was carried out on the full series of 2m segments composing the total length of 4 km, according to the Guidelines, six different risks, related to global structural and geotechnical behaviour, to local problems, seismic risk, road risk, geological risk, and hydraulic risk, were evaluated and an attention class was defined for the tunnel as “High”.