Effective Stress in Unsaturated Soils: A Thermodynamic Approach Based on the Interfacial Energy and Hydromechanical Coupling

In recent years, the effective stress approach has received much attention in the constitutive modeling of unsaturated soils. In this approach, the effective stress parameter is very important. This parameter needs a correct definition and has to be determined properly. In this paper, a thermodynamic approach is used to develop a physically-based formula for the effective stress tensor in unsaturated soils. This approach accounts for the hydro-mechanical coupling, which is quite important when dealing with hydraulic hysteresis in unsaturated soils. The resulting formula takes into account the role of interfacial energy and the contribution of air?Cwater specific interfacial area to the effective stress tensor. Moreover, a bi-quadratic surface is proposed to represent the contribution of the so-called suction stress in the effective stress tensor. It is shown that the proposed relationship for suction stress is in agreement with available experimental data in the full hydraulic cycle (drying, scanning, and wetting).     

Rock Porous Structure Characterization: A Critical Assessment of Various State-of-the-Art Techniques

Transport in Porous Media - The porous structure of geomaterials is of utmost importance for various industrial and natural processes. In this study, various conventional porous structure...     

A Capillary Water-Retention Framework for the Effective Stress Parameter Considering Hydraulic Hysteresis

Transport in Porous Media - The establishment of the representative elementary volume (REV) in studies of porous media is crucial for linking microscopic structure and pore-scale fluid...     

Investigating the effect of different asphaltene structures on surface topography and wettability alteration

This paper aims at investigation of the effect of asphaltene structure on wettability and topography alteration of a glass surface as a result of asphaltene precipitation. In order to provide a better insight into the topography alteration, a bi-fractal approach was employed. Such an approach is capable of discriminating topography alteration in two different surface types, namely, macro-asperities and micro-asperities. The observed variation of the fractal dimension in the two surface types could be considered as the consequence of different asphaltene sources. Therefore, the structure of different asphaltene sources was carefully examined. The effect of asphaltene structure is more pronounced for asphaltene precipitation at higher pressure. It was revealed that asphaltene particles of high complexity and with larger poly-aromatic rings tend to be detached easier at higher pressure than those with smaller poly-aromatic rings. Another evidence to emphasize the significance of asphaltene structure was given through wettability alteration. It was found that asphaltene particles with larger poly-aromatic rings turn the surface less oil wet at higher pressure. It seems that the difference in wetting condition and surface topography alteration of different asphaltene sources roots in their different structures.     

Bridging Effective Stress and Soil Water Retention Equations in Deforming Unsaturated Porous Media: A Thermodynamic Approach

The finite deformation of an unsaturated porous medium is analysed from first principles of mixture theory. An expression for Bishop’s effective stress is derived from (1) the deformation-dependent Brooks and Corey’s water retention curve and (2) the restrictions on the constitutive relationships of an unsaturated medium subject to finite deformation. The resulting expression for the effective stress parameter \(\chi \) is reasonably consistent with experimental data from the literature. Hence, it is shown that Bishop’s equation is constitutively linked to water retention curves in deforming media.