Stress Fluctuations in Driven Packings of Partially Saturated Granular Media

A granular packing compressed past its yielding point undergoes localized rearrangements which appear as stress drops in bulk stress-strain measurements. Previous research has demonstrated that the stress fluctuation behavior in dry granular materials is highly dependent on particle surface roughness and particle shape, and can be quantified using volatility, a measure of fluctuations borrowed from financial mathematics [1, 2]. Except in the case of smooth spheres, the behavior of driven granular systems in partial saturation remains poorly understood, and little work has been done on studying their fluctuation behavior. We investigate the volatility and shear strength in packings where the surfaces of 3D-printed grains are modified by the presence of a wetting fluid. We further discuss the dependence of the effective friction in such a packing on particle shape. Probing the local rearrangements provides insights about the intergranular forces supplied by these additives and presents a useful handle for tuning the mechanical responses of granular materials. 

 

[1]  Kieran A. Murphy, Karin A. Dahmen, and Heinrich M. Jaeger. "Transforming mesoscale granular plasticity through particle shape." Physical Review X 9.1 (2019): 011014.

[2]  Kieran A. Murphy, et al. "The intertwined roles of particle shape and surface roughness in controlling the shear strength of a granular material." Granular Matter 21.3 (2019): 1-6.