Influence of Clay Anisotropy on Model Simulations of Wetting Collapse

Recent interpretations of wetting-induced compaction revealed that water sensitivity can cause a loss of controllability in samples subjected to fluid injection. This paper elaborates these findings by focusing on fabric anisotropy, i.e., a feature of unsaturated clays not encompassed by previous studies. For this purpose, a hydromechanical elastoplastic model with rotational hardening is developed to capture fabric effects. The model performance has been validated under both saturated and unsaturated conditions with reference to laboratory tests on Lower Cromer Till (LCT). To inspect the role of the material properties, parametric analyses have been conducted, thus identifying the parameters which govern the transition from stable to unstable conditions upon wetting. The results show that fabric anisotropy affects only the deformations prior to wetting-collapse, without changing the value of suction at the onset of volumetric instability. By contrast, it is found that the model parameter governing the intensity of suction-hardening is able to alter the value of critical suction at the loss of control regardless of the intensity of fabric evolution. These results corroborate previous findings obtained through isotropic constitutive laws and emphasize the crucial role of hydromechanical constitutive couplings on the inelasticity of unsaturated porous media.