Strain-rate effects in dry and partially-saturated sand under one-dimensional compression at high pressures

This paper investigates the effect of strain rate on the behaviour of dry and partially-saturated sand at very high stresses, seeking to clarify the existence of a strain-rate dependence and how this is affected by changes in moisture content. Quasi-static one-dimensional compression tests on a fine quartz sand have been carried out to axial stresses of 800 MPa using the mac 2T multi-axial test rig at The University of Sheffield, alongside dynamic tests to 400 MPa using a split Hopkinson pressure bar. Specimens were prepared at moisture contents of 0.0%, 2.5% and 5.0%, and were laterally confined using a steel loading box or steel ring to ensure one-dimensional test conditions. Lateral stresses were recorded to allow the three-dimensional stress state of the specimens to be analysed. The results show that knowledge of both the axial and radial stresses is important for understanding the response of sand at higher strain rates, where an increase in stiffness is observed axially when compared to the quasi-static results