PSI - Issue 62

Nicola Perilli et al. / Procedia Structural Integrity 62 (2024) 538–545 539 2 Nicola Perilli, Stefano Stacul, Massimiliano Lombardi, Nicola Nenci, Nunziante Squeglia / Structural Integrity Procedia 00 (2019) 000 – 000 This is an open access article under the CC BY-NC-ND license ( https://creativecommons.org/licenses/by-nc-nd/4.0 ) Peer-review under responsibility of Scientific Board Members Keywords: landslide; existing bridges; field sheet form; Diagnostic Area; Geomorphological Significative Area; Relevant Area 1. Introduction Referring to the available literature on landslide hazard assessment and on landslide susceptibility mapping (Guzzetti et al., 2012; Pardeshi et al., 2013), it clearly emerges that there are some constraints which must be identified before collecting and managing all the remote and ground data. The most important are the extent of the area to be surveyed and the Conditioning Factors to be investigated. Concerning the area to be surveyed, the two end-members range: • from a single and simple polygon often of limited extent compared to the source area, e.g. when the landslide (which may involve a part of the slope or the entire slope) threatens a single structure; • to a complex polygon or even to a cluster of polygons, e.g. when the source areas of the landslide are part of a larger area such as a sub-basin or even a basin of a mountain area. In the new Italian Guidelines (LLG) on existing bridges (MIMS, 2022), the area that should be surveyed for the assessment of landslide susceptibility, vulnerability and exposure (i.e., the factors that lead to the Landslide Class of Attention) is not clearly defined and the data required for the estimate of the parameters (primary and secondary), necessary for evaluating these factors, are limited in terms of: number of classes, range of the classes, number of categories, and types of categories. This work aims to define the key areas that should be investigated for the evaluation of primary ( activity , velocity, and magnitude ) and secondary ( extent of the interference , presence/absence of mitigation measures and overall reliability of the assessment ) parameters. Here, we also suggest the rearrangement of the workflow and a better clustering of the data, which must be collected during the Periodic Field Survey, required by LLG. Furthermore, to reduce some uncertainties and the arbitrariness of the technical staff in charge of data collection, it is useful that the selected primary and secondary parameters are supported by an adequate description of the evidence and/or indicators observed during the field investigations and allocated in the appropriate section of the Field Sheet Form. Based on the inspection activities and on the data collected in the technical reports of about 500 existing bridges (and of the relative surrounding areas) by the Authors and other Fabre Consortium members (Stacul et al., 2024) one of the two goals of this work is the identification of three key areas that must be investigated before and during the Periodic Field Survey. They are the Diagnostic Area, the Geomorphological Significative Area, and the Relevant Area, listed in order of extent starting from the largest one. Given that the Field Survey is aimed at evaluating the primary and secondary parameters of both Recognized and Potential landslides, and at characterizing the geomorphological and geological context (including the geotechnical properties of the materials) and the land use and cover, the characteristics and extent of the area to be investigated are described in the following. This proposal fills one of the gaps of the current version of the LLG. The Relevant Area and the surrounding Geomorphological Significative Area are the target areas to be investigated to fill the Field Sheet Form and therefore to characterize the landslide (when identified); the Diagnostic Area, which includes the Geomorphological Significative Area, is also necessary to evaluate the proneness to landslide of the area surrounding a bridge using the Italian Inventory of Landslide Phenomena (IFFI database, Trigila et al., 2021) and the Italian Landslide Hazard Map (Trigila et al., 2021) among the others. Here below are reported the main characteristics of the proposed key areas: 2. Discussion and suggestions 2.1. Key areas to be investigated