Estimating spatial distributions of hydraulic parameters for a two-scale structured heterogeneous lignitic mine soil

The hydraulic properties are calculated from the measured bulk densities and texture data, using the Kozeny-Carman-equation for the saturated hydraulic conductivity, Ks, and the Arya-Paris approach for the water retention characteristics, ψ(θ). The effective porosity for Ks is reduced and the water retention increased in proportion to the lignite contents. Small-scale variability of hydraulic parameters is evaluated by using photographs of lignitic fragment distributions. For the discernable inclined layer structures, with a width of approximately 40 cm and a dip of 35°, Ks values in the range between 2.5 and 250 cm/d are estimated. The variability of the water retention characteristics is less pronounced. The predicted ψ(θ) functions are more comparable with loamy than sandy soils. The small-scale intra-layer variability of hydraulic parameters is higher than for lignite-poor mine spoil sediments and for most natural soils. The results may help to improve the analyses of flow and transport in lignitic mine soils by providing 2D two-scale parameter distributions for numerical simulations.