Variable cross-sectional pore model to describe hydraulic conductivity and water retention behaviors of geotechnical materials

To investigate the contribution of their non-uniform cross-section to hydraulic conductivity and water retention behaviours for geotechnical materials, the pores can be simplified as variable cross-sectional assembly of cylindrical macro-pores with pore throats. In addition, this variable cross-sectional pore model can provide theoretical expressions for both the saturated-relative hydraulic conductivity functions and the water retention curves based on a fractal pore size distribution. Finally, these theoretical expressions are validated against both the saturated-unsaturated permeability data for four sandstones and eight soils and the hysteretic water retention data (including the supplementary water retention tests on a clay) for three soils in the previous literatures. The results of RMSD between the predicted and the measured values of saturated permeability and relative hydraulic conductivity show that these new expressions are superior to Kozeny-Carman equation and Assouline model for describing the evolution of saturated permeability with porosity and the relation of relative hydraulic conductivity with effective degree of saturation.