Coupled water retention and shrinkage properties of a compacted silt under isotropic and deviatoric stress paths

Abstract

Although it is generally recognized that unsaturated soil behavior is governed by two constitutive variables (matric suction and net normal stress) and that the hydromechanical behavior of unsaturated soil is coupled, a water retention curve obtained from tests under zero stress and assuming no volume change is still fairly common. A relatively limited number of studies on the stress path–dependent water retention curve (SDWRC), particularly under a broader range of stress paths, exist in the literature. In this paper, the SDWRC, shrinkage curve, and swelling curve of a compacted silt subjected to isotropic and deviatoric stress paths are presented. The test results show that the air-entry value (AEV) increases, but the hydraulic hysteresis loop decreases with an increase in net mean stress. Furthermore, for a given stress level, the K0-compressed specimen exhibits higher AEV, but a smaller hysteresis loop than that of the isotropically compressed specimen. A nonlinear shrinkage curve is observed and the gradient of the post-yield shrinkage curve depends on the degree of saturation and net mean stress, but is independent of the stress path. For the range of suction studied, the gradient reduces with a decreasing degree of saturation, but with an increasing net mean stress. Finally, the test results are compared with the prediction of a model based on two independent constitutive stress variables.