Determination of strain-dependent soil water retention characteristics from gradation curve

The importance of soil water retention characteristics in modelling the hydro-mechanical response of unsaturated soils has been well recognised by many investigators in recent years. Determination of strain-dependent soil water retention curve (SWRC) is likely to be extraordinarily difficult. The first two authors have recently shown that SWRC can be computed from the gradation curve and the calculation result is consistent with the experimental results obtained from pressure plate tests. In this paper, based on a hypothesis related to change in the pore size distribution (POSD) due to volumetric strain of soil skeleton, a method to compute strain-dependent SWRC is presented. It is found that at initial degrees of saturation higher than 0.8, the influence of volumetric strain may be marginal whilst at initial degrees of saturation lower than 0.8, its influence is likely to be substantial. In all cases, the gradation curve of the soil affects the SWRC.