Interpretation of stresses and strains in unsaturated fine-grained soils

Measurements of specimen distortion in the triaxial cell are limited to axial and radial straining and volume changes. These represent the macro-mechanical straining of a specimen and must satisfy the overall continuity and work criteria. The internal strains at the micro-mechanical level are of greater magnitude as they need to account for a number of identifiable energy-dispersion components that do not necessarily give rise to net macro-mechanical strains. But micro-mechanical straining must also satisfy compatibility and energy-dispersion requirements and it is their net effects that give rise to the macro-mechanical straining. This includes the straining at the level of structure defined by the aggregates (combined volume of water and soil particles) and air voids in unsaturated fine-grained soils. In other words the distortional straining at the aggregate level must add up to give the net macro-mechanical straining. An analysis and discussion on triaxial experimental data and the significance of the stresses and strains at the aggregate level are presented.