PSI - Issue 84

Antonio Sannino et al. / Procedia Structural Integrity 84 (2026) 890–897

892

• Level 2: Data from Levels 0 and 1 are used to compute a preliminary risk score for each 20-meter tunnel segment, across six thematic areas. These scores, categorized as low, mid-low, mid-high, or high, determine the frequency of future inspections and inform maintenance priorities (Alessio et al., 2024); • Levels 3 & 4: For segments identified with mid-high risk scores in Level 2, a preliminary safety evaluation is conducted, followed by detailed numerical and structural analyses at Level 4 to investigate the factors contributing to elevated risk; This structured, multilayered approach enhances risk management by fostering a proactive maintenance strategy tailored to tunnel infrastructure conditions. At Level 2, an Attention Class (CdA) is assigned to each segment, categorized as high, medium-high, medium-low, or low, based on the assessment of hazards, exposure, and vulnerability. This classification process considers both available data and inspection results. Several risk types are accounted for based on the tunnel’s structural and environmental context. These include: • Global structural and geotechnical risks, such as interactions between the tunnel structure and geological conditions; • Localized structural risks, including those related to non-structural elements; • Seismic risk; • Road-related risks; • Geological risks, including landslide potential; • Hydraulic risks; The estimation of risk is expedited by expert judgment, typically involving a multidisciplinary decision-making team led by a designated Tunnel Officer. This expert panel relies on the data gathered during Levels 0 and 1 inspection to inform their judgments.

Fig. 2. Example of the Attention Classes along the tunnel

The overall CdA for the tunnel is determined by the most critical segment, guiding where resources should be allocated for additional investigations, further safety evaluations and, eventually, monitoring or intervention. It is important to note that a high CdA does not necessarily indicate an immediate or imminent risk; rather, it highlights the necessity for increasing the knowledge about the asset. It identifies sections of the tunnel that warrant additional inspections or continuous monitoring to ascertain whether a significant risk exists. When the Level 2 risk assessment identifies a moderate to high-risk category, a preliminary safety evaluation (Level 3) is conducted to examine the underlying factors contributing to the elevated risk within the thematic area. If the elevated risk is confirmed, engineering judgement and computational analysis (Level 4) are used to assess the residual safety factor of the identified mechanisms of failure and, where necessary, to define appropriate mitigation strategies or monitoring systems aimed at maintaining the risk at an acceptable level. In cases where the risk is assessed to be critically high, the Level 3 evaluation may be bypassed. 2. Tunnel Management System ARGO ARGO is a state of the art, cloud-based platform designed to manage large-scale infrastructure inspections (Foria et al., 2024), with a focus on tunnel safety and maintenance. It includes both a mobile app and a desktop platform, capable of processing over 600 laser scanner surveys to deliver precise, high-resolution 3D data on tunnel conditions.