This work proposes a theoretical framework for the permanent deformation calculation of unsaturated granular materials. The approach is based on the separation of the Soil Water Retention Curve (SWRC) into three linear phases. This representation makes unique the wetting and drying paths with a newly defined normalized suction s/s*. The same unique curves of permanent deformations with the normalized suction value are then developed.

The proposed approach is initially applied to reproduce the experimental permanent deformation of two granular materials with different water contents on the wetting and drying paths. The effect of the deviatoric stress on the permanent deformations is also considered in the multi-stage loading tests. The good correspondence between the predicted and experimental results confirms the good capacity of the proposed approach.

Finally, the proposed approach is injected in a finite difference code to model the tests performed on the two aforementioned granular materials. The numerical simulations show that both modeling concepts with variable and non-variable suction profile predict well the experimental results of the single-stage and multi-stage tests. The maximum deflection of a typical pavement is also estimated at the different hydraulic states, giving more credits to the proposed approach.

这项工作为不饱和粒状材料的永久变形计算提供了理论框架。该方法基于将土壤水分保持曲线（SWRC）分为三个线性阶段。该表示法以新定义的归一化吸力s / s *使润湿和干燥路径变得独一无二。然后，绘制出具有归一化吸力值的永久变形的相同唯一曲线。

最初将所提出的方法应用于在湿润和干燥路径上重现两种含水量不同的颗粒状材料的实验性永久变形。在多阶段载荷试验中还考虑了偏应力对永久变形的影响。预测结果与实验结果之间的良好对应关系证实了所提出方法的良好能力。

最后，将所提出的方法注入有限差分代码中，以对在上述两种颗粒材料上执行的测试进行建模。数值模拟表明，具有可变和不变吸力分布的两种建模概念都可以很好地预测单阶段和多阶段测试的实验结果。在不同的水力状态下，还可以估算出典型路面的最大挠度，使该方法具有更多的功劳。