Energy dissipation can macroscopically synthesize the evolutions in the microstructure of the marine clay during cyclic loading. Hence an energy-based method was employed to investigate the failure criterion and cyclic resistance of marine clay. A series of constant-volume cyclic direct simple shear tests was conducted on undisturbed saturated marine clay from the Yangtze Estuary considering the effects of the plasticity index (IP) and cyclic stress ratio (CSR). The results indicated that a threshold CSR (CSRth) exhibiting a power function relationship with IP exists in marine clay, which divides the cyclic response into non-failure and failure states. For failed specimens, the development of energy dissipation per cycle (Wi) with the number of cycles (N) exhibited an inflection point owing to the onset of serious damage to the soil structure. In this regard, the energy-based failure criterion was proposed by considering the inflection point as the failure point. Consequently, a model was proposed to quantify the relationships between failure energy dissipation per cycle (Wf) [or failure accumulative energy dissipation (Waf)], initial vertical effective stress, IP, and the number of cycles to failure (Nf,E). An evaluation model capturing the correlation among CSR, IP, and Nf,E was then established to predict the cyclic resistance, and its applicability was verified. Compared with the strain-based cyclic failure criterion, the energy-based failure criterion provides a more robust and rational approach. Finally, a failure double-amplitude shear strain (γDA,f) evaluation method applicable to marine clay in different seas was presented for use in practical geotechnical engineering.

中文翻译：

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基于能量的循环载荷作用下海洋粘土破坏准则和抵抗力评估方法


能量耗散可以在宏观上综合海洋粘土在循环加载过程中微观结构的演变。因此，采用基于能量的方法来研究海洋粘土的破坏准则和循环阻力。考虑塑性指数 （IP） 和循环应力比 （CSR） 的影响，对长江口未受扰动的饱和海相粘土进行了一系列恒定体积循环直接简单剪切试验。结果表明，海洋粘土中存在与 IP 呈幂函数关系的阈值 CSR （CSRth），它将循环响应分为非失效和失效状态。对于失效的试件，由于土壤结构开始严重破坏，每循环能量耗散 （Wi） 与循环次数 （N） 的发展表现出拐点。对此，通过将拐点视为失效点，提出了基于能量的失效准则。因此，提出了一个模型来量化每周期失效能耗散 （Wf） [或失效累积能耗 （Waf）]、初始垂直有效应力 IP 和失效周期数 （Nf，E） 之间的关系。然后建立了捕获 CSR、IP 和 Nf、E 之间相关性的评估模型来预测循环电阻，并验证了其适用性。与基于应变的循环失效准则相比，基于能量的失效准则提供了一种更稳健、更合理的方法。最后，提出了一种适用于不同海域海洋粘土的破坏双振幅剪切应变 （γDA，f） 评估方法，用于实际岩土工程。