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International audience; The present paper tackles the problem of the impact of a dry granular avalanche-flow on a rigid wall of semi-infinite height. An analytic force model based on depth-averaged shock theory is proposed to describe the flow-wall interaction and the resulting impact force on the wall. Provided that the analytic force model is fed with the incoming flow conditions regarding thickness, velocity and density, all averaged over a certain distance downstream of the undisturbed incoming flow, it reproduces very well the time history of the impact force actually measured by detailed discrete element simulations, for a wide range of slope angles.

Rocexs 2017, Barcelone, ESP, 23-/05/2017 - 25/05/2017; International audience; In the project AERES (Analysis of Existing Rockfall Embankments of Switzerland) small-scale quasi-2D-experiments had been done with embankments with stones placed parallel to the slope and stones placed horizontally. The experiments showed that rotating cylinders act-ing as impactors may surmount an embankment with batter 2:1, even if the freeboard is cho-sen to 1.5 times the block diameter. So a slope with an inclination of about 60° and equipped with rockery in general does not guarantee that a freeboard of one block diameter will be suf-ficient as described by the Austrian standard. During the test series also a block with an octagonal cross section had been used. This block, with no or only very low rotation, on the other hand was not able to surmount an embankment with rockery and a freeboard of about 0.8 times the block diameter. The evaluation of test data showed additional that the main part of energy dissipation occurs during the first 6 ms of the impact process. At least 75% to 85% of the block's total kinetic energy will be transformed into compression work, wave energy and heat when the block hits the embankment.

Colloque avec actes et comité de lecture. Internationale.; International audience; Les ouvrages constitués de filets métalliques constituent une solution innovante pour contenir les matériaux solides transportés par les écoulements torrentiels. Pour caractériser la réponse de ces ouvrages lors du chargement dû à l'écoulement, et à l'accumulation progressive des matériaux, un modèle de l'ouvrage a été développé par la méthode aux éléments discrets. Les composants métalliques de la structure sont modélisés par des éléments discrets cylindriques interconnectés. Les modèles du matériau en mouvement et du filet ont été validés grâce à des données expérimentales de laboratoire. Les simulations révèlent les mécanismes mobilisant les différents organes composant le filet et fournissent des pistes pour l'optimisation de ces structures.

International audience; This study presents a model for simulating the impact behavior of dry granular flow against a rigid wall using Discrete Element Method (DEM). The simulations were carried out using poly-dispersed clumps consisting of two overlapping spherical particles accounting for the shape effects of gravel particles. The particles were flowing in an inclined flume where different inclination angles were tested and interaction forces with the wall were recorded. The model calibration was in particular based on particle shape and flow thickness measurements. Compared with the experimental results, the model showed good agreement regarding the peak impact force, the time of the peak force and the final (residual) force at the end of the tests.

International audience; This paper presents a numerical model based on Discrete Element Method (DEM) used to reproduce a series of tests of dry granular flow. The flow was composed of poly-dispersed coarse-grained angular particles flowing in an inclined flume and interacting with a divided rigid wall. The normal impact force against the wall has been studied in details considering the force on each part of the wall. The model has been calibrated based on the flow thick-ness measurements. By quantitative comparison with experimental data, the model showed good agreement in terms of peak force on each part of the wall, the time of the peak and also the residual force values at the end of the tests.