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Fig. 10. The effect of pore size and pore connectivity on the water retention curve. (A) The drainage was calculated with the morphological pore network model for the sand material with particles ranging from 300 to 900 µm ("network"). The dry sand sample was analyzed with X-rays from synchrotrons with a resolution of 11.5 µm. The size of the image was 900 by 900 by 300 voxels. The modeled retention curve corresponds well to the water retention curve measured in the laboratory by Ursino and Gimmi (2004). The computed and measured drainage curves are compared with the cumulated pore-size distribution ("size"). In the latter case, connectivity is neglected and all pores with low capillary forces drain out. (B) The cumulative pore-size distribution ("size") was compared with the computed drainage curve ("network") for the sand sample with fine particles of size 100 to 200 µm. The pore structure of the dry sand sample was measured with a resolution of 3.5 µm using X-rays from synchrotrons. The image size was 1000 by 1000 by 100 voxels. By neglecting the connectivity of the pore space, the water saturation was underestimated.
