CT derived porosity distribution and flow domains

Computed X-ray tomography images of dry undisturbed soil samples of the coarse sandy loam of Korkusova Hut (KH) and the fine sand of Hupselse Beek (HB) are analysed concerning the image resolution, the direction of scanning and the evaluation of boundaries between the fast and slow flow domains. The image resolution appears to be a less important factor than the direction of scanning. Additional data sets are recommended for partitioning the fast and slow flow domains. Comparison is made with the tracer breakthrough pictures, magnetic resonance (MR) images and outflow volumes obtained from infiltration outflow experiments. The two soils under study appeared to have essentially different flow dynamics. In the KH sandy loam soil, the fast flow occurs in regions of high local porosity. In case of the HB fine sand, the sample appeared to consist of a dense part, where the flow process took place, and a more porous part, which stayed dry. Flow instability was detected on MR images for the KH soil. (C) 2002 Elsevier Science B.V. All rights reserved.