New insights into the 1963 Vajont slide using 2D and 3D distinct-element method analyses

The 1963 Vajont rock slide is studied using the distinct-element method (DEM). Two-dimensional (2D) and three-dimensional (3D) DEM models were constructed based on information published in the literature. In this study, a strength reduction approach was used to calculate the slide surface friction angles required for stability. The influence of several parameters was investigated in 2D, namely the reservoir water level, the shear stiffness of the slide surface, the rock mass strength, the rock mass deformability and rock joint patterns. Of the parameters which have been investigated, the most important parameter was found to be the reservoir water level. The rock mass deformability, which is neglected by other investigators, is also found to be important. From the 3D analyses, the failure friction angle was found to be sensitive to the assumptions made on the eastern boundary, and could affect the failure friction angle by approximately 3 degrees. The slope was found to exhibit signs of failure beginning from phi(slide_surface) = 26 degrees before complete loss of resistance at phi(slide_surface) = 18 degrees. It also emerges that, although the eastern end of the slope is the first to exhibit signs of movement, the displacements at the western end of the slope become larger than the ones at the eastern end as the stability of the slope reduces. Finally, this study showcases some useful numerical techniques developed ad hoc for DEM analyses to investigate the stability of large-scale slopes.