Sample geometry affects water retention curve: Simulation and experimental proves

3D virtual network was numerically constructed from particles of various sizes and the drainage process was simulated. The resulting moisture retention curves suggested that the sample geometry affects the drainage. This unexpected result was confirmed experimentally for water retention curves of sandy and loamy soil samples differing only in air accessible surface: 19.6 cm(2) (open surface) and around 0.8 mm(2) (paraffin covered surface with an opening made by injection needle). Experimental water retention curves differed markedly below pF = 2 and less at higher suctions, confirming the theoretically predicted behavior. The experiment did not confirmed a second hypothesis that water retention depends on sample diameter and height. Two open surface sandy soil samples (5 cm/5 cm and the second - 2.6 cm/2.0 cm; diameter/height) had very similar water retention curves. Possibly the specimens had too close diameter/height ratios.