This paper reports a comprehensive study on applying Capillary Rise Method (CRM) to measure the contact angles of soils. Contact angle quantifies the physicochemical interactions at the liquid-solid interface and is therefore critical to many physical processes involving the interaction of soil and water. In geotechnical engineering, such interactions are the basis for the formulation of the Soil Water Characteristic Curve (SWCC). However, the role of contact angle in SWCCs has not been adequately recognized. A modified CRM was proposed. Experiment results for virgin specimens demonstrated good repeatability; while for sieved soils, clear trends were observed in the variations of contact angle with respect to pore size. Contact angles much greater than zero were observed for all of the tested specimens which contradicts the assumption of perfect wettability in previous SWCC studies.
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