Roles of Particle Breakage and Drainage in the Isotropic Compression of Sand to High Pressures

Abstract

The roles of particle breakage and drainage conditions on the quasi-static compression response of sand were evaluated by comparing the results from drained and undrained isotropic compression tests on dry and saturated specimens up to a mean total stress of 160 MPa. For dry sand specimens, the compression curves from drained and undrained tests were similar because of the high compressibility of air. The isotropic compression curves of the dry sand specimens at mean stresses greater than 30 MPa reflect a transition toward void closure, reaching a minimum void ratio of 0.04 at 160 MPa. Dry sand specimens with different initial relative densities showed similar behavior during isotropic compression in drained conditions for mean stresses greater than approximately 30 MPa. As expected, saturated sand specimens tested under undrained conditions showed a much stiffer response than in drained conditions, with a bulk modulus greater than that of water. Increasing trends in particle breakage quantified using breakage factors from the literature with increasing mean stress were observed for the dry sand specimens, but negligible particle breakage was observed for the saturated sand specimens tested in undrained conditions. To highlight the linkage between particle breakage and transition to void closure at high mean effective stress, an empirical relationship was developed using a breakage factor from the literature to match the experimentally-derived compression curves of dry sands under drained conditions.