Linking hydraulic conductivity and tortuosity parameters to pore space geometry and pore-size distribution

Abstract

To enable a link between the pore size distribution of the soil measured in two dimensions and the hydraulic conductivity, a factor, which includes the connectivity and tortuosity of the pore network in three dimensions, is needed. In order to increase confidence in the models which predict hydraulic conductivity, this paper aims to gain insight into relationship between tortuosity and connectivity parameters used in statistical models of hydraulic conductivity and soil structural form measurements derived with image analysis. The analysis was based on a dataset of the hydraulic and soil structural properties of 19 Vertisol samples from Eastern Australia. The soil structural data were measured on large (200 mm height and 150 mm diameter) cores at 5–7 depth slices. Several soil structural form parameters, including a pore size distribution, were calculated using an image analysis program ( Solicon v2.1). The hydraulic conductivity model developed by Kosugi [Soil Sci. Soc. Am. J. 63 (1999) 270] based on the lognormal pore size distribution was fitted to measured hydraulic conductivities. Hydraulic conductivity was strongly related to porosity and a measure of connectivity in the horizontal direction (pore genus). The tortuosity parameters α and β from the Kosugi [Soil Sci. Soc. Am. J. 63 (1999) 270] model were related to the mean pore size, with increasing mean pore size indicating decreasing tortuosity of the sample.