Creep behavior in Virginia Beach sand

Abstract

Triaxial compression tests were performed on dense specimens of Virginia Beach sand at low and high confining pressures to study time effects that relate to grain crushing due to static fatigue or delayed fracture. Experiments to study effects of loading strain rate on subsequent creep showed negligible time effects and no grain crushing at low confining pressures, while tests at high confining pressures indicated increasing amounts of creep with increasing initial loading strain rates and with increasing deviator stress at creep. Investigation of effects of grain-size distribution indicated stiffer initial response and smaller amounts of creep for more uniformly graded soils at high confining pressures. The experimental results showed that structuration effects were not present in the dense Virginia Beach sand. A long-term creep test at high confining pressure indicated continuous creep with no indication of its termination. Sieve analyses following each triaxial test showed that grain crushing, as quantified by Hardin’s relative breakage factor, was proportional to energy input and amount of creep observed for each soil specimen. The creep is due to the time-dependent static fatigue by which the grains crush and cause rearrangement of the grain structure, and this is the reason behind the time effects in granular materials.