It is known that the soil-water characteristic curve (SWCC) contains important information for understanding the engineering behaviors of unsaturated soils. Best fit equations (or SWCC equations) are commonly used for the representation of the SWCC. As the infiltration into the unsaturated soil is mainly governed by the hydraulic properties of soil, the SWCC equations play important roles in the assessment of the rainwater infiltration. In this paper, four types of SWCC equations were adopted and different applicable suction ranges for four best fit equations are investigated and discussed. The fitting parameters and input values in these best fit equations are also demonstrated and discussed. The residual volumetric water content (or residual saturation) as defined in the original equations was recommended to be considered as an input value for a rough estimation of the residual condition. Parametric studies were also carried out to investigate the effects of different fitting parameters on the estimation of SWCC variables and hydraulic conductivities.

众所周知，土壤-水特征曲线（SWCC）包含重要信息，有助于理解非饱和土壤的工程特性。最佳拟合方程式（或SWCC方程式）通常用于SWCC的表示。由于对非饱和土壤的入渗主要取决于土壤的水力性质，因此SWCC方程在评估雨水入渗方面起着重要作用。本文采用了四种类型的SWCC方程，并对四种最佳拟合方程的不同适用吸力范围进行了研究和讨论。还演示并讨论了这些最佳拟合方程式中的拟合参数和输入值。建议将原始方程式中定义的残余体积水含量（或残余饱和度）视为粗略估计残余条件的输入值。还进行了参数研究，以研究不同的拟合参数对SWCC变量和水力传导率的估计。