Run Out of Landslides - Continuum Mechanics versus Discontinuum Mechanics Models

In general, a rock slope failure leads to the detachment of a rock mass consisting of a mass of blocks. During the last few years continuum mechanics as well as discontinuum mechanics numerical codes have been developed for modelling the run out of these masses. In order to compare both methods, Punta Thurwieser Rock Avalanche and Frank Slide were modelled by the continuum mechanics numerical code DAN3D as well as by the distinct element method PFC3D modified for run out modelling. The simulations showed that the parameters necessary to get results coinciding with observations in nature are completely different and that Frank run out was a real “slide” of a coherent mass, whereas Punta Thurwieser run out was a rock mass fall with much internal movement. The parameters for a run out simulation, therefore, have to be chosen in such a way that the simulation gives a rock mass fall in one particular case and a slide of a coherent mass in another, corresponding to the real conditions. Therefore, the prediction of the run out kinematics and the fixing of the parameters is a demanding task in each case when modelling run outs.