Comparison of field and laboratory soil-water characteristic curves

Results of field monitoring of moisture content and matric suction at the crest and berm of a large cut slope in completely decomposed granite in Hong Kong are reported. Field moisture content and matric suction clearly show that the volumetric water content increases as a result of rainfall infiltration and decreases as a result of evaporation. Correspondingly, the matric suction decreases due to rainfall infiltration and increases due to evaporation. Soil-water characteristic curves at different depths at the crest and near the berm of the cut slope are determined from the field data. Unlike soil-water characteristic curves determined in the laboratory by testing small specimens, the field measured soil-water characteristic curves show negligible hysteresis. Engineering implications of the field soil-water characteristic curves are discussed.