Consolidation of surfactant-laden unsaturated porous media

This work is concerned with the influences of surfactants on the poromechanical response of unsaturated porous materials. Surfactants modify the surface tension at the interface between the wetting and nonwetting fluids in the interconnected pores thereby affecting the mechanical and hydrological responses of unsaturated media. This work employs a Biot-type poroelasticity theory for unsaturated porous media with a surfactant-modified capillary modulus to investigate the coupled fluid transport and deformation in surfactant-laden unsaturated porous materials. Analytical expressions of pore pressures and settlement in a finite porous column filled by a wetting fluid and a nonwetting fluid are obtained using the Laplace transform method. Numerical results for a clay texture contaminated by perfluorooctane sulfonate (a major PFAS compound) show that the pore water pressure decreases with an increase in the aqueous PFAS concentration. On the other hand, the pore air pressure is increased by the presence of the PFAS. The surface displacement also increases with an increase in the PFAS concentration. Finally, the influences of the PFAS on the pore fluid pressures and deformation become less significant at high water saturations towards the saturated moisture content in the clay.