Chemomechanical behavior of multiphasic porous media: Conception and formulation

November 9, 2017

Chemomechanical behavior of multiphasic porous media: Conception and formulation

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Presenter: Changfu Wei

Abstract: Physicochemical effect remains elusive, either experimentally or theoretically, in poromechanics. In this talk, I present a new theoretical approach to modeling the chemomechanical behavior of multiphase porous media, in general, and unsaturated soils, in particular, which can address skeletal deformation, fluid flow, heat conduction, solute diffusion, chemical reaction, and phase transition in a consistent and systematic way. In this context, the concepts of matric potential and matric suction are redefined, and the chemical potential of a fluid species is formulated with explicitly accounting for the effects of osmosis, capillarity, and adsorption; the composition of pore water pressure is identified, and explicit formulations are developed for the effective stress and intergranular stress with considering physicochemical effects. It is shown that the negative water pressure measured by a conventional transducer can be significantly different than the true pore water pressure. It is also theoretically revealed that, other than the soil-water characteristic function, a new pressure (or potential) function accounting for the physicochemical effects is generally required in analyzing the coupled chemo-mechanical processes in unsaturated soils. The new theory is capable of explaining many salient phenomena occurring in water-saturated porous media with a degree of saturation varying from an extremely low value to 100%, including Donnan osmosis, capillary fringe, air entry value, initial hydraulic head during seepage and pressure solution. 

Bio: Professor Changfu Wei obtained his PhD from the University of Oklahoma in 2001. Now he is a senior research fellow at the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, and a joint professor at the School of Civil Engineering and Architecture, Guilin University of Technology. He is also the Vice Director for the State Key Laboratory of Geomechanics and Geotechnical Engineering of China. His research interest is focused on the coupling of the multiple physical and chemical processes in multiphase geomaterials such as unsaturated soil, frozen soil and gas hydrate-bearing soils. He has authored and coauthored more than 120 journal papers and has received more than 23 patents.