Applicazione di modelli reologici tempo dipendenti nell'evoluzione di deformazioni gravitative profonde

A preliminary analysis of the effects of creep on the development of a deep-seated gravitational slope deformation (DSGSD), carried out by numerical modeling, is described. The slope rock mass evolution has been simulated applying different creep rheological models. The studied DSGSD is located in the Central Italian Alps (Val S. Giacomo). It is characterized by three main scarps, different sets of tensile trenches, and counterscarps, mapped during a detailed geomorphological survey. The mechanical behaviour of the rock masses, in terms of elastoplastic parameters, has been defined on the base of laboratory and in situ tests. In order to simulate this instability process a stress-strain-time numerical modeling has been applied by a finite difference numerical code (FLAC). First, the slope conceptual model was represented by a constant dipping slope, uniform lithology (ortogneiss) and the presence of the water table at different elevations. The effects of different constitutive model laws have been considered: the visco-elastic Maxwell model; the visco-elastic Burger model and the elasto-visco-plastic Burger model. The modeling has been performed simulating the melting of the ancient glacier, starting from its maximum load. Because of the difficulty to determine rock mass creep parameters, for each of the rheological models a sensitivity analysis has been performed, varying the physical-mechanical properties. In accordance with the geological data, milonitic zones, characterized by low mechanical properties, have been introduced in the middle part of the slope, and two weathered superficial layers have been added, identifying new instability processes.The elasto-visco-plastic Burger constitutive model develop a stress/stain system more consistent with the present morphology.