Failure and post failure conditions of a landslide involving weathered and degraded rocks.

The paper deals with stability conditions of a landslide occurred in a town of Calabria, Southern Italy, during the winter 1998-1999. The slope is constituted by outcropping gneissic and granitic rocks that are strongly weathered and degraded. In depth the rock mass is characterised by wide zones of completely degraded rock that are associated to tectonic sub-horizontal structures. The displacements produced by the last activation caused cracks and strong deformations in the paving of an important national road, moreover they caused the opening of large and deep fractures in the slope. The trigger cause is not directly correlated to pluviometric events. Emergency monitoring of displacements allows to delineate some characteristics of the post failure conditions and to individuate the slope instability s geometrical features. The cognitive outline includes a geotechnical characterisation and it permits to define a preliminary geotechnical model and to effectuate a sensitivity analysis of slope stability conditions.