3D numerical simulation of the Tolosa rock avalanche in Argentinean Andes.

BODIN X.; MOREIRAS S.M.; DAUDON D.; CUERVO S.

Jornada; Jornadas de estudio CUIA Infraestructura para la energía: mitigación de riesgos naturales y sustentabilidad ambiental.; 2016

The Tolosa rock avalanche (Mendoza, Argentina) was simulated using a Discrete Element Model (DEM) code specifically designed by 3SR lab (Richefeu et al., 2012). This code simulates rockfall taking into account the behaviour of blocks falling down interacting together in an avalanche movement and with the initial topography. Because of scaling effects in geometry and processes, the application to event of the Andes required some adaptation of the parameters: energy restitution rate, enlargement of the topography, volume of the movement and of the particles, high elevation difference, and poor initial data availability. In order to test the potential of this code, the choice of the Tolosa Pleistocene rock avalanche relies on the accessibility of the valley and the deposits, the strategic place near the international road Nº 7 connecting Mendoza (Argentina) with Santiago (Chile), the ease for the photographic data collection ; the visible blocks are not to numerous in sense of pertinence of using DEM modelling comparing to continuous modelling, but the scale factor regarding alpine events modelled by Cuervo et al. (2014) is a challenge in the determination of the mechanical parameters involved as some other phenomena may be of importance (crushing of the blocks for example). Preliminary steps to run the DEM simulations include: Structure-from-Motion (SfM) processing of the terrestrial photographic images collected on the field in May 2014 in order to get a high resolution (5-m pixel spacing) topography (especially for the scar rock wall); merging of the resulting Digital Terrain Model (DTM) into a 20-m resolution SPOT DTM in order to fill the gaps in the SfM's DTM; manual (expert-based) reconstruction of the initial topography of the terrain at the rock avalanche's deposit place; choice of the mechanical parameters in relation with geological considerations and simulation of the blocks propagation with real deposit comparison.