ABSTRACT

The collapse of bulk granular materials is of increasing importance in many applications in engineering and geophysics including processing of oil-sands and analysis of avalanches and landslides. The present work is primarily aimed at modelling of the deposition of tailings. This requires predicting the geometry of stable granular heaps, which poses a particular difficulty to available CFD models. In this paper we introduce a new plasticity model for the frictional stresses within the bulk granular material. The numerical simulations employ a two-fluid, one the granular material and the other the surrounding fluid, mixture approach to model the two-phase fluid-granular flow. Solution of the governing equations is carried out using COMSOL code. Results for two cases with small and large aspect ratios are presented. The results show the evolution of the internal flow and shape of the granular heap. The simulations examine the role of the height-to-length ratio on the final shapes. The results include comparisons between the present computations and available experimental measurements.

INTRODUCTION AND MOTIVATION

Flow and collapse of granular materials is a topic of increasing interest in several industries including agriculture, pharmaceutical, petroleum, and mining. Hazard prevention and risk mitigation in case of avalanches, landslides and similar geophysical disasters are not possible without adequate knowledge about the physics of the collapse of granular media. The majority of papers on the topic includes experimental studies on how granular columns collapse under the gravity. The focus of the experimental studies is mainly on the final profile of the slumps after the material comes to rest. Among the published results are scaling laws relating the final height and foot length (the final runout) of the collapsed media to initial aspect ratios (the initial height to the initial horizontal extent). In addition, effects of different grain sizes with different internal friction angles on the final profiles are usually studied.

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