Volume change behavior of collapsible compacted gneiss soil

The mechanical behavior of a compacted metastable-structured residual gneiss soil was experimentally investigated. Volume changes were investigated using both a conventional oedometer cell and a triaxial permeameter system where the stress state variables were independently controlled. Wetting stress paths were utilized to reflect field conditions associated with collapsing earth structures. The compacted specimens were consolidated under both isotropic and k(0)-oedometer conditions. Measurements of total volume change and water content change were made at specified matric suction values following a wetting stress path under a given loading. The experimental data were analyzed to define volume change constitutive relationships for the metastable-structured soil. Best-fit modeling was used for predicting the volume change behavior of the compacted metastable-structured residual soil during wetting-induced collapse. The measured data are discussed from both phenomenological and microscopic viewpoints. Predictions of the best-fit models are compared to experimental results.