3D SEEPAGE ANALYSIS OF A LANDSLIDE BASIN IN A TECTONISED TURBIDITIC FORMATION

By governing the pore pressure distribution and, consequently, the available shear strength of the soil, the hydrogeological regime of a hillslope can significantly influence landslide activity. This study investigates the hydrogeology of the Pianello hillslope, in Bovino (Daunia Apennines), characterized by a basin of slow-moving landslides in a complex geo-hydro-mechanical setup, dominated by a tectonised clayey flysch. A conceptual hydrogeological model was developed—upon a previously built lithological model—using piezometric monitoring data and permeability tests. Subsequently, 3D steady-state seepage analyses were performed assuming a homogeneous soil model to estimate the position of the water table and the pore pressure distribution in the hillslope. The analysis showed a good agreement with measured pore pressures, especially in the central portion of the hillslope, accurately predicting high piezometric levels at large depth, which are one of the main predisposing factors for slope instability. While the predictions were fair in the central part of the hillslope, discrepancies arose in other areas due to the inherent limitation of the assumed homogeneous soil model to capture complex hydrogeological discontinuities. Future work will incorporate distinct geotechnical units and explicit modelling of highly permeable rock interlayers to enhance prediction accuracy across the entire basin.