During undrained cyclic loading, clayey soils experience substantial stiffness and strength degradation when subjected to shear amplitudes exceeding a critical threshold. This paper presents an enhanced bounding surface rate‐independent plasticity model, an evolution of the previous SANICLAY model, tailored to capture this specific behavior during cyclic loading. A distinguishing feature of the proposed model is the introduction of an activation mechanism. This mechanism triggers degradation modeling based on the applied cyclic shear amplitude. To measure this amplitude, the activation mechanism incorporates a novel state variable that serves as a proxy for the applied cyclic stress. The effectiveness of the proposed model is demonstrated by comparing it to experimental data from various materials subjected to cyclic shearing under undrained conditions. The study encompasses a broad range of constant strain or stress amplitudes. Compared to the reference model, the proposed model exhibits improved predictive accuracy for the stress‐strain response of clays at small amplitudes of cyclic loading and large number of cycles. Furthermore, it accounts for strength degradation due to cyclic loading.

中文翻译：

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边界表面塑性中粘土循环降解的激活机制

在不排水循环荷载过程中，当剪切幅度超过临界阈值时，粘土会经历显着的刚度和强度下降。本文提出了一种增强的边界表面速率无关塑性模型，它是先前 SANICLAY 模型的演变，专门用于捕获循环加载期间的这种特定行为。该模型的一个显着特征是引入了激活机制。该机制触发基于所应用的循环剪切幅度的退化建模。为了测量这个幅度，激活机制结合了一个新的状态变量，作为所施加的循环应力的代理。通过将其与不排水条件下循环剪切的各种材料的实验数据进行比较，证明了所提出模型的有效性。该研究涵盖了广泛的恒定应变或应力幅度。与参考模型相比，所提出的模型在小振幅循环加载和大量循环下对粘土的应力应变响应表现出更高的预测精度。此外，它还考虑了由于循环载荷导致的强度下降。