Methodology for numerical simulation of Tolosa rock avalanche in Argentina.

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

Lyon

Conferencia; RSS Rock Slope Stability conference; 2016

Because of their tectonic settings and the presence of an extended high-altitude cryosphere (snow, glaciers, permafrost), the central Andes are highly impacted by gravitational movements like rock avalanches, rockfalls or landslides. Between Mendoza (Argentina) and Santiago de Chile (Chilei), the Road 7 is a strategic axis for the South American economy, suffering from a large variety of endangering phenomena. Recently, Moreiras et al. (2005) mapped past (Holocene and Pleistocene) events using geomorphological evidences. In order to increase the pertinence of this work for elaborating hazard risk maps, numerical modelling is a promising tool (Corominas 2014). We used a Discrete Element Model (DEM) code developed at 3SR to simulate real rock avalanches propagation in France (Cuervo 2014). Because of scaling effects in geometry and processes, the application to events of the may require adaptation of the parameters introduced: mechanical energy restitution rate, enlargement of the topography, volume of the rock blocks, high elevation difference, and poor initial data availability. The choice of the Tolosa pleistocene Pleistocene rock avalanches relies on the accessibility of the valley and the deposits, the strategic place near the road, the ease for the photographic data collection. Preliminary steps to run simulations include: Structure-from-Motion (SfM) processing of images collected on the field in May 2014 in order to get a high resolution (5m 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 (xpert-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 in order to simulate the blocks propagation and run-out distance .