Discrete modelling of stress relaxation in crushable sands based on fracture theory

Abstract

Stress relaxation of quartz sand is simulated using a recently proposed physically based time-to-fracture discrete element method (DEM) framework. The relaxation of stress on sands under high confining pressure is modelled using stress-corrosion induced grain fracture. This feature is embedded into a pre-existing particle-splitting based rough crushable model for Fontainebleau sand. A controlled on-off computational strategy is adopted to advance the simulation. The computed oedometer stress relaxation curve compares favourably with previous experimental results. Triaxial stress relaxation results indicate that stress relaxation increases linearly with time. Contact forces become more homogenous during stress relaxation; as a result, the sample becomes more stable. These microscopic behaviours agree with some observations in pile ageing, suggesting that the model may be adopted directly to investigate such engineering scale phenomena due to its conceptual simplicity, computational efficiency and ease of calibration.