Aging of Sands as a Micromechanical Process

J. K. Mitchell, N. R. Suarez, T. L. Brandon
dem, Discrete element method, micromechanical, Sands, Simulation, Soil, X-ray CT

Laboratory and field studies show that engineering properties of freshly deposited and disturbed granular materials change over time, under constant effective stress, and with little or no change in void ratio, during a process commonly known as aging. Even though the effects of aging in sands have been reported by numerous investigators, the driving mechanisms are still not completely understood. X-ray computed tomography (CT) was used to study changes in the internal structure of specimens of sand taking place during aging. Results from the X-ray CT were compared with discrete element method (DEM) simulations, which modeled rate-dependent particle interactions. The analyses showed that the internal structure of sands changes during aging. Soil grains move and rotate over time, redistributing the stress within the soil structure. Computer simulations indicate that the internal redistribution of the stress causes significant changes to the macroscopic properties of particle assemblies, which resemble the effects of aging in granular soil reported in the literature.

Keywords: DEM, Discrete Element Method, Simulation, X-ray CT, Sands, Micromechanical, Soil

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