基于颗粒级配曲线预测非饱和土持水曲线的物理方法

Physical approach to predict water retention curves for unsaturated soils based on particle-size distribution

持水曲线模型中若含有未知经验参数,则可能会降低对持水曲线预测的可靠度。为此,对土样颗粒级配曲线上划分的粒组分别构建形如立方体的天然土颗粒以及理想球体颗粒集合体,依据这两者的几何特征和物理性质推得其比例关系;基于粒组信息、干密度以及土粒密度提出了计算土孔隙半径和持水曲线的物理方法,无需引入未知经验参数。最后,利用非饱和土水力特性数据库UNSODA中40个土样的持水试验结果对该方法进行了验证,通过计算基质吸力预测值及其实测值之间的均方根残差(RMSR)发现物理方法的RMSR在0.179~0.833范围内变化,并对其中37个土样的持水曲线预测精度优于含有两个未知经验参数的传统Arya模型。

Unknown empirical parameters in water retention models may reduce the reliability of prediction. The cube-shaped assemblages of natural soil and idealized spherical particles are developed according to the fractions from particle-size distribution. On the basis of geometry and physical properties, a relationship of proportionality between them is then proposed to provide a physical approach for computing pore radii and water retention curves of soils from particle-size fractions, bulk density and particle density without incorporating unknown empirical parameters. Finally, the physical approach is validated against the test data of water retention for a total of forty soil samples from the hydraulic property database UNSODA. The results of RMSR between the predicted and the measured values of matric suction show that the distribution of RMSR values ranges from 0.179 to 0.833. This physical approach is also superior to the traditional Arya model which requires two unknown empirical parameters for describing the water retention curves for thirty seven of the forty soil samples.