Local and Global Volumetric Strain Comparison in Sand Specimens Subjected to Drained Cyclic and Monotonic Triaxial Compression Loading

This article investigates the development of volumetric strain nonuniformities in sand specimens subjected to drained cyclic triaxial compression loading. The assessment is performed by comparing volumetric strain determinations using an external volume gauge and local axial and radial strain measurements mounted on the center of the specimen. The experimental investigation has been performed for both frictional and enlarged lubricated ends on sand specimens of different densities and fabricated using both moist tamping and dry deposition techniques. It will be shown that considerable discrepancies between the global and local volumetric determination arise even in specimens tested with enlarged lubricated ends, as a result of different volumetric tendencies (contraction or dilation) of the center and the boundaries of the specimens. These discrepancies are more pronounced for dense specimens cycled at high average stress ratios and amplitudes. The influence of three different assumptions employed to account for the specimen’s deformed profile (namely the right cylinder, parabolic, and sinusoidal profile) on the local volumetric determinations will be also assessed. Some recommendations for the need for local volumetric measurements will be attempted.