The existed understanding of stress-dilatancy behavior is predominantly based on experiments conducted with clean quartz sand, with limited research focusing on coral sand. Particularly, impacts of fines and density state on stress-dilatancy response of marine coral sand is of significant concern. This work presents a systematic investigation into these issues through meticulously controlled geotechnical tests, coupled with corresponding discussion and interpretation. Results show that at a high stress level, both pure coral sand and its mixtures consistently undergo shear contraction regardless of fines proportion and density state. However, mixtures with minimal fines experience shear contraction initially, followed by dilatancy under a medium-low stress level. Friction angle at peak state (φps) and critical state (φcs), excess friction angle (φex), and maximum dilatancy angle (ψmax) decrease powerfully as increasing fines content. Besides, the lower and upper limits of variation for φps, φcs, φex concerning ψmax were presented. Correlation between φex and ψmax highlights that Bolton's stress-dilatancy equation, developed for pure sand, remains applicable provided that fines content remains below the threshold value. Additionally, gray correlation result suggests that fines post the dominant influence on above behaviors, followed by density state and stress level. Finally, potential mechanism behinds the influences of fines and density state was explored from the view of particle column buckling.

中文翻译：

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掺入非塑性细粉的海洋珊瑚砂的应力-膨胀行为


对应力-膨胀行为的现有理解主要基于对干净的石英砂进行的实验，有限的研究集中在珊瑚沙上。特别是，细粒和密度状态对海洋珊瑚砂应力-膨胀响应的影响是一个值得关注的问题。这项工作通过精心控制的岩土工程测试，以及相应的讨论和解释，对这些问题进行了系统调查。结果表明，在高应力水平下，纯珊瑚砂及其混合物无论细粉比例和密度状态如何，都会持续发生剪切收缩。然而，具有最小细粉的混合物最初会经历剪切收缩，然后在中低应力水平下发生膨胀。峰值和临界状态 （φcs） 的摩擦角 （φcs）、超摩擦角 （φex） 和最大膨胀角 （ψmax） 随着细粉含量的增加而大幅减小。此外，还给出了 φps、φcs、φex 关于 ψmax 的变化下限和上限。φex 和 ψmax 之间的相关性突出表明，只要细粉含量保持在阈值以下，为纯砂开发的 Bolton 应力-膨胀方程仍然适用。此外，灰色相关结果表明，细粉对上述行为的影响占主导地位，其次是密度状态和应力水平。最后，从颗粒柱屈曲的角度探讨了细粉和密度状态影响背后的潜在机制。