Three-dimensional numerical modelling of the Passo della Morte landslide (UD, Italy) for the design of risk mitigation measures

The work is focused on the study of the Passo della Morte landslide, the so-called landslide 3, located in northern Italy, in Province of Udine (UD). The landslide is moving at an extremely slow rate of 2-3 cm/year and has been studied for more than 15 years due to the presence of a road tunnel that crosses it. Several features that characterise the Passo della Morte area and that are considered interesting for the purpose of building the reference geological and numerical models of landslide 3 have been described. At first, an overview of the methods for the slope stability analysis has been carried out. The main part of the work has been focused on the building of a numerical model of the landslide. The main objective of the modelling was to obtain a representation of the phenomena similar to those observed with surveys and monitoring. The reference data have been taken from the monitoring devices present on the landslide body and in the surrounding area. In order to model the landslide, the commercial software RS3 has been used; it is a three dimensional analysis software based on the finite element method. In order to build a reference model, a series of test models was built. Once obtained the reference geometry and defined the geomechanical parameters, the model was calibrated comparing its results with the data coming from the monitoring. The similarity between observed displacements and those shown by the model, and the minimal difference between the results obtained using two different failure criterions are a confirmation of the reliability of the model. The analysis was repeated implementing a groundwater surface defined based on a hydrogeological map of the area. The new results confirmed the reliability of the model. Various attempts were done in order to implement the existing drainage adit and simulate its influence on the groundwater but problems in the definition of the boundary conditions did not permit to achieve satisfactory results.