Analysis of landslides reactivated by variation in the groundwater regime

Landslides can cause considerable damages to infrastructures and human lives. These phenomena appear in different kinematic forms: from extremely slow to extremely rapid. Although slow-moving slope movements do not frequently cause loss of human lives, they may damage structures, interrupt lifelines (highways, railways, pipelines) and require very high costs for their stabilisation. The aim of this research is to propose some approaches for the analysis of landslides controlled by changes in the pore pressure within the slope. In the first part, slow-moving landslides are analyzed. These landslides are characterized by the evidence that deformations are mostly concentrated within a narrow shear zone above which the unstable soil mass essentially moves as a rigid body. Two different approaches are proposed: the first one is a simplified method that is based on the infinite slope model to assess slope stability and on some analytical solutions to predict landslide mobility. The second one utilises a finite element approach in which an elasto-viscoplastic constitutive model in conjunction with a Mohr-Coulomb yield function is incorporated to describe the behaviour of the soil in the shear zone. For the other soils involved by the landslide, an elastic model is used for the sake of simplicity. A significant advantage of the present methods lies in the fact that few constitutive parameters are required as input data, the most of which can be readily obtained by conventional geotechnical tests. The rest of the required parameters should be calibrated on the basis of the available monitoring data concerning the changes in the piezometric levels and the associated movements of the unstable soil mass. After being calibrated and validated, both approaches can be used to predict future landslide movements owing to expected groundwater fluctuations or to assess the effectiveness of drainage systems which are designed to control the landslide mobility. These methods are applied to back-predict the observed field behaviour of three active slow-moving landslides documented in the literature. In the second part of the work, a landslide of large dimensions (about 6 million of cubic meters) that occurred in Maierato (Calabria) on 2010, after a long period of heavy rainfall is analyzed using a finite element approach in order to establish the main causes of the landslide event and to define the failure process occurred.