Field measurement of soil hydraulic properties characterizing water movement through swelling clay soils

Abstract

Determination of hydraulic properties in swelling clay soils is difficult due to seasonal variations in pore geometry and to soil structural heterogeneity, requiring large samples. Large in situ columns are therefore prepared to measure K sat and K unsat near saturation, using the crust test. Soil structure descriptions can be used to estimate optimal sample size. Infiltration into dry or moist clay soil with vertically continuous cracks involves preferential vertical movement of water along the cracks. The resulting irregular moisture distribution does not allow use of many common soil physical techniques, which require homogeneous moisture contents in isotropic soil.