Hydromechanical properties of unsaturated compacted loess considering initial structural strength attenuation under undrained conditions

The hydromechanical characteristics of unsaturated loess determine the engineering performance such as bearing capacity and stability of compacted loess structures. In this study, the volume change equation is constructed in the effective stress-saturation space by correlating soil compressibility with saturation. Meanwhile, a hydraulic model considering the influence of volumetric strain is introduced to develop a hydraulic-mechanical elastoplastic model for unsaturated loess. Furthermore, a stress ratio sensitivity parameter is developed to describe the initial structural strength attenuation of unsaturated loess under loading, introducing the sensitivity parameter to modified effective stress to characterize the hydromechanical behaviors under initial structural strength attenuation. The proposed model can well describe the coupling effect of hydraulic and mechanical wetting. Using the constraints of the saturation and volumetric strain relationship under undrained conditions, predictions of soil-water change are achieved via net stress and deviatoric stress driving. And then the excellent performance of the proposed model in predicting the hydromechanical behavior of unsaturated compressed loess under undrained conditions is verified.