Comparison of testing techniques and models for establishing the SWCC of riverbank soils

The soil water characteristic curve (SWCC), also known as soil water retention curve (SWRC), describes the relationship between water content and soil suction in unsaturated soils. Water content and suction affect the permeability, shear strength, volume change and deformability of unsaturated soils. This paper presents results of the laboratory determination of the SWCC for soil samples obtained from the riverbank of the Lower Roanoke River in North Carolina. Six different testing methods were used to establish the SWCC including the filter paper, dewpoint potentiameter, vapor equilibrium, pressure plate, Tempe cell and osmotic methods. It is concluded that each suction measurement technique provides different measurable ranges of suction values, and the combined results from the different tests provide continuous SWCCs. Three widely available models were also shown to adequately fit the experimental SWCC data, particularly for matric suction values under 1500 kPa. These results will be valuable to practitioners in deciding which methods to use to establish the SWCC, and which empirical relationship to use for modeling the SWCC of riverbank soils.