Landslide susceptibility evaluation in Alpine environment: 1. 3D Finite Element modeling of the Ruinon (IT) case study

This manuscript is Part 1 of two companion papers that explore a multidisciplinary approach to predict velocity and stability of a large landslide located in the Central Italian Alps: the Ruinon landslide. The area is of high geological interest due to the presence of numerous shallow and deep gravitational instability processes that affect valley flanks, mainly driven by unfavorable morphological conditions and geomechanical properties of rock masses. In this manuscript, a 3D finite element model (FEM) was implemented in order to analyze the stress–strain distribution along the Ruinon rock-slope. Goals are to define the relation between morphological factors, mechanical parameters and the development of irreversible strains. The model was defined based on morphological features and mechanical properties detected along the slope, as well as on piezometric data from the landslide monitoring system. In a first step of the analysis, a static simulation was carried out under dry conditions. Then, a validation process was performed by comparing numerical outputs with geomorphological field observations. Finally, a parametric analysis was carried out where different piezometric level scenarios were evaluated in order to assess the influence of both mechanical parameters and pore pressure on the distribution of high sliding susceptibility areas. By overlaying satellite images with the model outputs, results were shown to accurately reproduce the extent of the slope areas subject to active gravitational instability. Parametric analyses showed a clear relationship between the input factors and the magnitude of strain, while the extension of areas subject to irreversible deformation did not change significantly. Stress distribution and stress–strain relations defined in this article are subsequently introduced in a thermos-hydro-mechanical (THM) numerical model presented in Part 2 of this work, where the evolution of the Ruinon landside is simulated.