Time-dependent model for sand grain deflection including contact maturing under sustained load

Abstract

The hypothesis of contact maturing advocates static fatigue at contacts between sand grains as the key cause contributing to time effects in sand. The focus of the paper is on a model of an individual grain subjected to a sustained load applied through two steel plates. The grain is characterized by the roughness of its surface. The distinct element method is used to construct a model on two scales: the grain scale and the contact scale. Assemblies of bonded sub-particles are used to model both the grain and the contact region. The bond model includes the stress corrosion process, which simulates decaying strength of bonds and fracture. Two components of the time-dependent grain deflection under sustained loads are the displacement owed to sub-critical fracturing of asperities on the grain surface at the contacts and the creep of the core mineral in the grain. The model demonstrates what may be difficult capturing in physical testing. The simulated nominal contact evolves as the number of contact points increases due to sub-critical fracturing of asperities, leaving the contact firmer. The contact evolution process, as observed in simulations, is consistent with the contact maturing hypothesis.