Soil-Water Characteristic Curve Equation with Independent Properties

The soil-water characteristic curve (SWCC) has traditionally been represented using equations whose fitting parameters do not individually correspond to clearly defined soil properties or to features of the curve. As a result, unique sets of parameters are often nonexistent, and sensitivity analyses and statistical assessments of SWCC parameters become difficult. In order to overcome these difficulties, a new class of equations to represent unimodal and bimodal SWCCs is proposed. The chosen fitting parameters are the air-entry value, the residual suction, the residual degree of saturation, and a parameter that controls the sharpness of the curvatures. The physical meaning for the soil parameters is discussed for different soil types. A unique relation between each of the equation parameters and the individual features of SWCCs is assured. The proposed equations are fitted to data corresponding to a variety of soil types and a good fit is observed.