Applicazione di codici di calcolo 3D e 2D per l'analisi dei fenomeni di crollo nei pressi del Passo Gardena (Sud Tirolo)

Rock falls are the most common landslide phenomena in the Alpine Arch. According to a survey commissioned by the Provincial Office of Bozen in 1995, rock falls are the most frequent type of instability phenomena. Near the Gardena Pass - an important pathway that connects Dolomites valleys frequented by tourists throughout the year- a steep rocky wall can be found with large rock masses that are a threat both to the road and the traffic. To identify which mitigation works could best solve the problem, the Provincial Office of Bozen - in collaboration with the Geological Departements of Modena-Reggio Emilia and Trieste Universities - chose to analyse run out distances and kinetic energies by performing rock fall simulations. The first stage of the study saw the application of 3D software Rotomap, as the complex fall motion of a rock boulder is more precisely defined by means of a calculation code that also takes into account lateral deviations. Starting from a video showing a face scaling operation on the wall under consideration, a back analysis was conducted to calibrate restitution coefficients Rn and Rt. Rotomap results were then confronted with the simulation outcomes obtained with Rocfall - the software most commonly used by geologists and engineers. The fact that slopes are quite close to the road and the high kinetic energies obtained with 3D and 2D software simulations highlighted scaling of all potentially unstable blocks as the only possible solution to mitigate the risk of rock falls in the Gardena Pass.