Multi-scale particle morphology evolution in rotating drum tests: Role of particle shape and pore fluid

Abstract

During the downslope long-distance movement of debris avalanches, particles interact with each other in various modes, by rolling, sliding and colliding with each other. During transport, grains may undergo breakage, changing in size and shape. However, research on debris avalanches at the grain scale remains limited, in particular, the evolution of grain morphology at different scales, from the overall form down to surface roughness, with runout distance. This paper investigates the evolution of particle morphology of granite gravel particles during long distance travel using a rotating drum, Micro-Deval apparatus, together with three-dimensional (3D) image analysis with a 3D laser scanner. The effects of particle shape and pore fluid (dry, saturated with water or slurry) on the evolution of particle morphology during transport were investigated. It was found that while the gravel was strong enough to resist the fragmentation that could be induced by the inter-particle actions during testing, the corners and edges became rounded, and the general form and surface roughness remained unaffected by the particle interactions. The more angular the grains, the easier the corners to be abraded during interaction. The change of local roundness of the grains was amplified in water-saturated conditions and suppressed in a slurry-saturated medium. The viscosity of the pore fluid, rather than initial particle shape, was critical in controlling the particle morphology evolution.