Normal Compression Planar Surfaces for Specific Volume and Degree of Saturation

The glasgow coupled model (GCM) predicts unique unsaturated normal compression planar surfaces for specific volume and degree of saturation when the soil states are at the intersection of the mechanical (M) and wetting retention (WR) yield curves. More generally, the model predictions for any stress path where plastic volumetric strains (compression) and plastic increases of degree of saturation occur simultaneously correspond to stress states on these two planar surfaces. The existence and form of these planar surfaces has been only validated against isotropic compression data on unsaturated samples of compacted Speswhite kaolin, but their suitability to represent one-dimensional (1D) loading conditions remains unclear. This paper investigates this aspect by deriving equivalent expressions for 1D normal compression conditions and then comparing them against the experimental response of unsaturated samples of compacted Jossigny silt subjected to 1D compression paths at different constant values of matric suction