Abstract The strain evolution of saturated clays under cyclic loadings has been studied by means of various laboratory testing methods, aiming for the accurate simulation of engineering conditions such as the consolidation states of clays, cyclic stress paths of external loadings and boundary conditions in situ. Considering that the subgrade clays are usually overconsolidated rather than normally consolidated, the drainage condition is normally partially drained instead of undrained under long-term cyclic loadings, and the cyclic stress paths are in three-dimensional stress state, this study explores the three-dimensional strain characteristics of both normally and overconsolidated clays in partially drained condition based on a true triaxial apparatus. Emphasis are put on the effects of cyclic stress ratio (CSR), overconsolidation ratio (OCR) and coefficient of cyclic intermediate principal stress (bcyc) on the accumulation of permanent strain components including major, intermediate, minor principal strains, and volumetric strain. Test results show that the relative magnitudes of strain components are strongly influenced by both bcyc and OCR, while the accumulated directions of strain paths tend to be identical for various bcyc values. The increase of bcyc leads to a linear growth of permanent volumetric strain for both normally and overconsolidated clays, while the permanent major principal strain shows a firstly increasing and then decreasing trend versus the increase of bcyc. For the normally consolidated and overconsolidated clays, the largest permanent major principal strains are achieved at around bcyc = 0.4 and 0.2, respectively. The accumulation of permanent intermediate principal strain is always promoted by the increase of bcyc. In addition, the development of permanent major principal and volumetric strains with cycle number is analyzed in the double logarithmic plane, which are found to be combined by two linear parts.

中文翻译：

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三维应力条件下循环荷载下饱和粘土的应变演化

摘要 利用各种室内试验方法研究了循环荷载作用下饱和黏土的应变演化，旨在准确模拟原位黏土固结状态、外荷载循环应力路径和边界条件等工程条件。考虑到路基粘土通常是过固结而不是正常固结，在长期循环荷载作用下排水条件通常是部分排水而不是不排水，循环应力路径处于三维应力状态，本研究探讨了三维应力状态。基于真三轴装置的部分排水条件下正常和超固结粘土的应变特性。重点放在循环应力比 (CSR) 的影响上，超固结比 (OCR) 和循环中间主应力 (bcyc) 系数对永久应变分量的累积，包括主要、中间、次要主应变和体积应变。测试结果表明，应变分量的相对大小受 bcyc 和 OCR 的影响很大，而对于不同的 bcyc 值，应变路径的累积方向趋于相同。bcyc 的增加导致正常和超固结粘土的永久体积应变线性增长，而永久主要主应变随 bcyc 的增加呈先增加后减小的趋势。对于正常固结和超固结粘土，最大的永久主应变分别在 bcyc = 0.4 和 0.2 左右实现。bcyc 的增加总是促进永久中间主应变的积累。此外，在双对数平面内分析了循环数的永久主主应变和体积应变的发展，发现它们由两个线性部分组合。