Conference Dates

June 18-21, 2006


When checking the behaviour of large landslides, deterministic stability analysis has little sense. Stability coefficients can only be seen as the relationship between acting and reacting forces. In fact, large landslides simply move in any case, more or less quickly. When stable, the displacements are actually so small that they aren't detectable. Thus the so called security factor could always be set to unity, and the computations performed as back analysis. The transition from a very slow viscous displacement to a catastrophic failure is better described in a change of rheological behaviour than in an overtaking of a stability coefficient. Actors of such changes are in most cases the hydrodynamic and hydrogeological conditions, related to external factors such as climatic changes, weathering, natural or artificial deforestation, etc. Two cases located in the south Alps, one in Switzerland and the second in Italy, involving weathered metamorphic rocks are taken as illustrating examples.