水-力耦合特性是非饱和土最基本的力学特性之一，含黏粒土体的孔隙结构对含水率变化非常敏感，相应的孔隙分布曲线也会随之变化。基于已有的试验研究成果，揭示了水力路径下土体微观结构的演化规律，建立了孔隙比与孔隙分布曲线之间的关系，由此提出了一个能模拟干化过程中孔隙分布曲线变化的理论模型。所建立模型中，吸力增加后的孔隙分布曲线可由初始曲线通过平移、缩放以及分散三步得到；其中孔隙分布的平移量和缩放量与孔隙比线性相关，而分散程度与孔隙比满足指数衰减关系。模型预测结果表明，所建立的模型不仅能预测集聚体间和集聚体内孔隙分布的变化，而且能较好地反映中间态孔隙分布曲线的变化。

The hydro-mechanical coupling is the basic characteristics to the unsaturated soil, especially to the one which consists of clay particles. Pore structure of clay is sensitive to the water content; and the pore size distribution (PSD) changes at every moment during drying process. The evolution laws of microstructure under the hydraulic path are first summarized based on experimental results. Subsequently, a novel model is developed by relating the pore-size distribution to the void ratio. According to the model, the PSD can be transformed from the initial PSD through three steps: translation, scaling and dispersion. The quantity of displacement and scaling are linear with void ratio; and the dispersion is exponential attenuation with void ratio. Finally, the model predictions are compared with experimental measurements in the literature, showing that the new model is capable of describing the microstructure evolution of unsaturated soil during drying process.