Using microscope observations of thin sections to estimate soil permeability with the Kozeny-Carman equation

In this study we used the Kozeny-Carman (K-C) equation as a semi-physical model for estimating the soil permeability using data derived from microscope observations. Specific surface areas and porosities were obtained from two-point correlation functions derived from scanning electron microscope images of thin sections using a magnification of 50 and a resolution of 1.88 μm pixel^-1.Permeabilities were predicted using two published ('Ahuja' and 'Berryman') and one generalized variant of the K-C equation. The latter model was similar to the Berryman variant, but used a free parameter C rather than a porosity dependent formation factor. All K-C model variants were optimized on measured permeabilities. The Ahuja and Berryman K-C models performed relatively poorly with R² values of 0.36 and 0.57, respectively, while the generalized model attained R² values of 0.91. The parameter C was strongly related to texture and, to a lesser extent, particle density. The general model still required measured surface area and porosity. However, we showed that it was possible to estimate these parameters from texture resulting in an R² of 0.87. A fully empirical model that did not assume K-C concepts performed slightly worse (R² = 0.84). The results indicate that after developing the model using microscope information, only macroscopic data are necessary to predict permeability of soils in a semi-physical manner with the K-C equation.