Relationship between the Soil-Water Characteristic Curve and the Suction Stress Characteristic Curve: Experimental Evidence from Residual Soils

The part of effective stress resulting from soil moisture or soil suction variation can be defined by the suction stress characteristic curve (SSCC). For a given soil, the SSCC can be experimentally determined from shear-strength tests. Recent work shows that the SSCC can be uniquely linked to the soil-water characteristic curve (SWCC). The uniqueness of the SSCC determined from both shear strength and soil moisture retention tests is examined for several residual soils in Korea. The validity of the effective stress principle is demonstrated by showing that effective stress-based on the SSCC describes the same unique failure criterion as that for the saturated failure criterion. The measured SSCCs are also shown to predict the soil-water retention curves within a few percentage. The SWCCs of these residual soils, determined directly from soil moisture retention tests, also accord well with the SSCCs determined directly from triaxial shear-strength tests with the difference within several tens of kPa. Therefore, we show that the suction stress characteristic curve or soil-water retention curve alone can be used to describe both the effective stress and soil-water retention characteristics of variably saturated soils.