This technical paper focuses on evaluating the shear strength of unsaturated sand at drying, wetting and alternate drying–wetting cycles, as well as the correlation between the strength and the water retention curve (WRC) at different hydraulic phases. Results of stress–strain curves and WRCs were obtained from conducting numerous tests using suction-controlled triaxial test. Although the maximum shear strength was obtained from the specimens under drying conditions, the difference between the drying and wetting shear strength was relatively small for the tested soil. Based on analysis of the test results, a multi-surfaces envelope model was proposed to fit the experimental shear strength data under drying conditions and to predict the shear strength under wetting conditions (or any subsequent drying–wetting cycle) based on the drying fitting parameters. The fitting and prediction performance of the proposed equations were checked using experimental data from previous studies, and very good agreement was reported. Moreover, the WRC was found to be capable of not only estimating unsaturated soil property functions but also anticipating the soil shear strength behaviour under different hydraulic phases.

该技术论文的重点是评估不饱和砂在干燥，湿润和交替的干湿循环中的剪切强度，以及在不同水力阶段强度与保水曲线（WRC）之间的相关性。应力-应变曲线和WRC的结果是通过使用吸力控制三轴试验进行的大量试验获得的。尽管最大的剪切强度是在干燥条件下从样品中获得的，但是对于测试土壤，干燥和湿润剪切强度之间的差异相对较小。根据对测试结果的分析，提出了一种多表面包络模型，以拟合干燥条件下的实验剪切强度数据，并基于干燥拟合参数预测润湿条件（或任何后续的干燥-润湿循环）下的剪切强度。使用先前研究的实验数据检查了所提出方程的拟合和预测性能，并报告了很好的一致性。而且，发现WRC不仅能够估计不饱和土壤的性质函数，而且能够预测在不同水力相下的土壤抗剪强度行为。