PSI - Issue 84

Antonio Fiorentino et al. / Procedia Structural Integrity 84 (2026) 749–756

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chosen according to the literature that consider that infiltration rarely in this silty clayey material may exceed 1 mm/h, so 24 mm/d, that was rounded to 25 mm/d. The comparison shows that, in 2022–2023, cumulative rainfall is systematically higher than the mean (Fig. 5a): by the end of the hydrological year, cumulative rainfall reaches approximately 740–750 mm, compared with ~640–650 mm for the mean value. Moreover, in late spring the 2022–2023 curve also exceeds the statistical variability range, indicating a persistent anomaly. Monthly cumulative rainfall indicates that the deviation is mainly driven by a few months: May 2023 about 150 mm versus ~65 mm on average (close to 2× the mean). In terms of antecedent wetting, the combined April–May 2023 rainfall therefore totals approximately 230 mm, compared with ~105 mm expected on average, in a period when soil fracture can favor infiltration phenomena.

Fig. 5 - Total and monthly cumulative rainfall in 2023 recorded at the Valsinni rain gauge station.

To have better evidence of the infiltration effects, cumulative rainfall were compared with the piezometric excursions of the water table gauge station (Terra Montonata) (Fig. 6), not far from the studied area. It is evident that after a very rainy period, the water table remains above the average value (-5.20) giving evidence of the rainfall supply. The movement in June 2023 was also preceded by a period of very well-distributed and constant rainfall, which led to a rise in the water table between May and June . The hydrological analysis conducted shows that rainfall sequences, even if not intense but well-distributed, gave rise to significant infiltration phenomena that facilitated the reactivation of the flow.

Fig. 6 - Comparison of cumulative rainfall values and groundwater levels for the period November 2022-june 2023.

7. Conclusion The case history of the deformations of Fortunato Viaduct is a singular example of interaction between an earthflow and a viaduct built to over cross this landslide area. The geomorphological evolution of the flow through retrogressive and overlapping lobes of debris material meant that the latest reactivations of the flow ended up occluding the space