One-Dimensional Compression of Sands at High Pressures

A one-dimensional testing apparatus was developed to test soils to axial stresses up to 850 MPa. The apparatus was instrumented with strain gauges such that lateral soil stresses, and therefore K0 , could be inferred from measured circumferential strains. Three different initial densities of quartz, Cambria, and gypsum sands were tested and it was found that the effect of initial density was eliminated at high stress magnitudes. This stress magnitude was higher for mineralogically harder grains than for softer grains. The inferred values of K0 for the mineralogically harder Cambria sand was found to be constant at high pressures, but slightly below that indicated by Jaky's equation. However, the softer gypsum sand indicated increasing values of K0 as the stress magnitude increased. This apparently was caused by inelastic, viscous flow during shearing.