Undrained Volume Changes in Compacted Cohesive Soil

A comprehensive series of unconsolidated-undrained triaxial shear tests was conducted on a partially saturated compacted sandy clayey silt to evaluate the nature and extent of volume changes during undrained shear. The results showed high variability in the volume changes, which were also nonlinear and stress-dependent. It was found that the variations are affected by the soil type, soil structure, compaction method, compaction effort, and water content. The results also showed that the concept of critical void ratio-critical confining pressure is applicable for the analysis of undrained failure conditions in partially saturated, compacted soils of the type considered. These results are also interpreted in terms of a Poisson's ratio for analytical studies; the variability of this ratio serves to emphasize the importance of effective prototype modeling.