Transient groundwater flow in the Orvieto overconsolidated clayey slope (Central Italy). In situ monitoring and numerical modelling

The clayey slope of the Orvieto hill has been constantly affected by landslides phenomena in the form of slow movements and failure events. Rates of movements have been found to strongly depend on pore pressure dis-tribution, which is controlled by the transient groundwater flow induced by infiltrated rainfall. Monitoring data provided by twenty-year long records and new continuous measures through miniature pressure trans-ducers in Casagrande cells are compared to variation of pore pressure levels obtained from seepage analyses in transient conditions. Finally the effectiveness of simple empirical models that link piezometric levels to slope displacements assuming a viscous behaviour of the shear surface materials is discussed, with reference to the shallower translational slope movements.