PSI - Issue 84

Lorenzo Brezzi et al. / Procedia Structural Integrity 84 (2026) 473–480

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susceptibility and potential interaction mechanisms. The case studies presented in the following sections are discussed through this interpretative lens, with particular attention to how indirect evidence, mitigation works, and geomorphological context influence landslide risk assessment beyond what is suggested by cartographic information alone.

2. Inspection experiences from the field 2.1. Interpretative framework for inspections

Level 1 inspections represent a key step in landslide risk assessment, as they rely primarily on the interpretation of field evidence to refine the preliminary classification obtained during the census phase. In this stage, the reliability of the assessment strongly depends on the ability to correctly interpret geomorphological indicators and contextual elements, especially when landslide–bridge interactions occur through indirect mechanisms, and no observable structural damage is present. Based on the inspection experience gained in the Belluno province, a limited number of recurrent aspects emerged as particularly critical for avoiding the underestimation of landslide-related risk. These aspects do not constitute a rigid checklist, but rather interpretative elements that require expert judgment during on site surveys. The following case studies are presented with the aim of illustrating how these aspects can be identified in practice, and how specific field observations may significantly influence the interpretation of landslide susceptibility and interaction scenarios at the Level 2 phase.

2.2. Viaduct A

Fig. 1. Main cartographies related to landslide risk (IFFI and PAI) regarding the context of Viaduct A.

Although the maps did not indicate landslide phenomena directly interacting with the viaduct (Fig. 1), the structure is located in a valley characterized by several areas of high or very high landslide hazard. The only mapped movements consist of collapses or topples, which are common in the Belluno region. This case exemplifies how on-site inspection may significantly alter the conclusions drawn from a purely cartographic assessment, which showed no evidence of either potential landslide activity or past events affecting the structure. During the inspection, signals related to three different types of instability were identified, despite the absence of direct damage to the structure, which only exhibited piers with possible signs of local scour. From the road deck, a shotcrete-stabilized rock wall was clearly visible, together with an artificial rockfall protection gallery located a short distance upstream (Fig. 2c). Although these elements do not pose a direct hazard to the structure, they provide important information on the susceptibility of the surrounding slopes to collapses or topples potentially affecting the