SMALL-STRAIN BEHAVIOR OF FROZEN SAND IN TRIAXIAL COMPRESSION

The stress-strain behavior of frozen Manchester fine sand has been mea sured in a high pressure low-temperature triaxial compression testing system developed for this purpose. This system incorporates DC servomo tor technology, lubricated end platens, and on-specimen axial strain d evices. A parametric study has investigated the effects of changes in strain rate, confining pressure, sand density, and temperature on beha vior for very small strains (0.001%) to very large (>20%) axial strain s. This paper presents constitutive behavior for strain levels up to 1 %. On-specimen axial strain measurements enabled the identification of a distinct upper yield stress (knee on the stress-strain curve) and a study of the behavior in this region with a degree of precision not p reviously reported in the literature. The Young's modulus is independe nt of strain rate and temperature, increases slightly with sand densit y in a manner consistent with Counto's model for composite materials, and decreases slightly with confining pressure. In contrast, the upper yield stress is independent of sand density, slightly dependent on co nfining pressure (considered a second order effect), but is strongly d ependent on strain rate and temperature in a fashion similar to that f or polycrystalline ice.