Thermodynamic basis of unsaturated soil modeling

Upon an increase of moisture, unsaturated soil may collapse or swell, depending on the loading state and history. This important characteristic must be realistically reproduced by a constitutive model aimed for practical applications. In addition to collapse/swelling, other essential features, such as deformation and failure following arbitrary shearing paths, must also be realistically reproduced. It is conceivable that a comprehensive model capable of simulating all those responses should be based on a sound theoretical framework, and the universal physical laws of thermodynamics may serve as a basis for such a framework. This paper describes such a framework.