PSI - Issue 84

Michele Placido Antonio Gatto et al. / Procedia Structural Integrity 84 (2026) 111–118

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b)

Fig. 4. (a) Example of synthetic rainfall used for the assessment of potential soil slip triggering; (b) comparison of the triggering rainfall with the historical rainfall time series for percentile determination.

3. Calibration and application of the methodology to the Sondrio 1994 and Casargo 2019 cases For the calibration of the physical, mechanical, and hydraulic parameters of the SLIP model, as well as of the methodology described above, two soil slip events were considered: the Sondrio event of 7 January 1994 and the Casargo (LC) event of 6 August 2019. In both locations, shallow landslides affected infrastructure and urbanized areas. Figure 5 shows the landslide polygons recorded in the Italian Landslide Inventory (IFFI) corresponding to these events. In addition to “rapid flow” phenomena, “areas subject to widespread rockfalls and topples” are also indicated, confirming the overall susceptibility of the study areas. The analyses carried out using the X-SLIP platform were based on the Digital Terrain Model (DTM) and the Geological Map provided by the Lombardy Region Geoportal, as well as on daily rainfall data supplied by ARPA Lombardia. The slope angle was derived from the DTM following the procedure described in Gatto and Montrasio (2023). For the calibration of geotechnical parameters, average values of physical and mechanical properties derived from previous studies (Montrasio et al. 2011) were adopted, consistently with the lithologies present in the investigated areas. The slope drainage coefficient k t was calibrated so that the factor of safety FS computed using the SLIP model was lower than 1 on the day corresponding to the landslide reported in the IFFI database, while remaining consistent with the soil type. Table 1 reports the parameters used, including the triggering rainfall peak P30 and the corresponding percentile within the D1 distribution of daily rainfall.

Fig. 5. Landslide areas recorded in the Italian Landslide Inventory (IFFI) for the Sondrio and Casargo study areas.