RELATIVE DENSITY EFFECTS ON UNDRAINED SAND BEHAVIOR AT HIGH PRESSURES

A systematic investigation of the undrained behavior of sand at high pressures was performed to study the effects of initial relative density on the stress-strain, pore pressure, and strength behavior. Experiments were conducted on Cambria sand with initial relative densities of 30% and 60%, and the results are compared with previously published data for an initial relative density of 90%. Triaxial compression and extension tests were performed on cylindrical specimens with isotropic consolidation pressures in the range from 8 to 60MPa. Particle crushing played an important role in the observed behavior. Stress-strain, pore pressure, and strength behavior were found to be very similar and almost independent of initial relative density at high pressures, because the isotropic compression curves tend to merge once particle breakage becomes important at these high pressures. Effective stress friction angles for undrained compression and extension tests varied systematically in the range from 32° to 35° with slightly higher values for the compression tests. Interpretation of all results from the experimental study in terms of total stresses shows that sand at high pressures behaves similar to a normally consolidated clay.