Peak Shear Strength and Dilatancy of a Pleistocene Age Sand

Abstract

This paper summarizes results of laboratory investigations performed to quantify the influence of diagenesis (or aging processes) on the peak shear strength and dilatancy of an uncemented Pleistocene age sand sampled near Charleston, South Carolina. Drained triaxial compression tests were performed on high-quality intact specimens retrieved using the in situ freezing and sampling method, and on remolded specimens prepared with matching densities. The stress-strain behavior of intact specimens is accompanied by dilation and a peak shear value, whereas remolded specimens generally contracted throughout shearing. An age-dilatancy term is added to a dilatancy index equation to account for the difference between intact and remolded peak friction angles. The resulting equation suggests that dilatancies due to age and density are suppressed with increasing confining pressure. A profile of peak friction angle with depth is established from the results and compared with estimates from empirical relationships.