Hydro-mechanical modelling of landslides with a material instability criterion

The Petacciato landslide that occurred between 1906 and 1966 along a stretch of the Adriatic coast (Italy) and the Trevoux landslide that appeared in 1983 in France are analysed using Hill's material sufficient stability condition, which is based on the sign of the second-order work. Local and global sufficient stability criteria allow detecting and describing the instability phenomena, respectively, at the material point level and for the whole domain. By considering the non-associated Plasol elasto-plastic constitutive model and the second-order work criterion, it is shown that unstable stress-strain states can be reached in plane strain conditions, strictly inside the plastic limit criterion. The two landslides that occurred in Petacciato and Trevoux are then analysed by modelling unsaturated hydro-mechanical coupling. The analysis is carried out using the Lagamine finite element code. This original approach to slope stability analysis makes it possible successfully to exhibit the landslide mechanism observed on these slopes after a long rainy period: this could not be described with the classical methods.