PSI - Issue 84

Lorenzo Di Taranto et al. / Procedia Structural Integrity 84 (2026) 1007–1014

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drainage systems, often identifiable as sinkholes, which establish a direct hydraulic connection between the shallow sandy levels and the deep horizons of the landslide body. In geological contexts such as the Bradanic Foredeep, where Subapennine Clays alternate with marine sandy and silty deposits, the combined action of tectonic uplift, subsurface erosion and surficial opening, favored by gravitational deformation, promotes the development of piping phenomena, see Fig. 1b, which hydraulically connect the sandy layers with the surface. These structures act as natural conduits, allowing meteoric water to bypass the less permeable clayey layers and rapidly infiltrate toward the basal zones of the slope. The existence of such hydraulic connectivity has direct implications for the stability of the slope interacting with the 'Santo Stefano' viaduct, as it is capable of drastically reducing the hydraulic response time of the slope to rainfall events.

Fig. 1. (a) an overview of the "Santo Stefano" viaduct located along the S.S. 655 "Bradanica"; (b) detail of a sinkhole located on the upslope.

Fig.2. geological map of the study area (excerpt from the Geological Map of Italy 1:100,000, modified); fl – Terraced alluvial deposits from a fluvio-lacustrine environment; Qcs – Calcareous-quartzose sands; Qca – Blue-gray clays and marly clays (Subapennine Clays); red dot – Location of the "Santo Stefano" viaduct.