Water retention curve (WRC) is an important parameter for unsaturated soils. It is greatly affected by the anisotropy of pore structure, as supported by experimental results in the literature. So far, however, the mechanism and theoretical modelling of anisotropy effects have not been investigated. These two issues were explored in this study based on two-dimensional analysis of soil pores, while were approximated as a series of ellipses for simplicity. According to experimental results in the literature, the pores of anisotropic specimen are more elongated than those of isotropic specimen on average. The elongated pore has a higher water retention ability than the round pore when they have the same area. As a consequence, the water retention ability of anisotropic specimen is higher than that of isotropic specimen. On the basis of this mechanism, a new WRC model was proposed for isotropic and anisotropic soils . To verify the new model, it was applied to simulate the WRCs of three soils with isotropic and anisotropic pore structures. Measured and calculated results were well matched with the coefficient of determination (R²) in the range of 0.89 to 0.99 and the root-mean-square error (RMSE) ranging from 0.009 to 0.073. It is convincingly demonstrated that the new model is able to capture the influence of anisotropy on WRC.

保水曲线（WRC）是非饱和土壤的重要参数。孔隙结构的各向异性极大地影响了它，文献中的实验结果也证明了这一点。但是，到目前为止，尚未研究各向异性效应的机理和理论模型。在对土壤孔隙的二维分析的基础上，对这两个问题进行了研究，为简单起见，将它们近似化为一系列椭圆。根据文献中的实验结果，各向异性试样的孔平均比各向同性试样的孔长。当长孔具有相同的面积时，其具有比圆孔更高的保水能力。结果，各向异性样品的保水能力高于各向同性样品的保水能力。在这种机制的基础上，提出了一种适用于各向同性和各向异性土的WRC模型。为了验证该新模型，将其应用于模拟具有各向同性和各向异性孔结构的三种土壤的WRC。测量和计算结果与测定系数（R²）的范围为0.89至0.99，均方根误差（RMSE）的范围为0.009至0.073。令人信服地证明，新模型能够捕获各向异性对WRC的影响。