Loose granular materials may also exhibit instability behaviors similar to liquefaction under drained conditions, commonly referred to as diffuse instability, which can be studied through constant shear drained (CSD) tests. So far, the research on CSD in binary mixtures is still insufficient. Therefore, a series of numerical tests using the discrete element method (DEM) were conducted on binary mixtures under CSD path. The possible model of instability is categorized into type I and type II, type I instability occurs prior to reaching the critical state line (CSL), whereas type II instability occurs after exceeding the CSL. The study analyzes the macroscopic instability behavior and the impact of fine content (FC) on macroscopic instability behavior. The numerical results show that as FC increases, the slope of the instability line (IL) increases initially and then falls in the p‐q plane. In the e‐p plane, the IL decreases initially and then ascends. The instability type of the binary mixtures is influenced not only by relative density but also by FC. The stability index increased first and then decreased with the increase of FC. The microscopic origin of binary mixtures instability is explored by investigating the fabric‐stress relationship. The collapse of the weak contact sub‐network triggers the specimen instability, while the strong contact sub‐network dictates the difficulty of achieving instability. FC influences the evolution of fabric anisotropy of the strong and weak contact networks, thereby controlling the macroscopic instability behavior of binary mixtures.

中文翻译：

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恒定剪切排水应力路径下二元混合物的不稳定性：宏观和微观视角的洞察


松散的颗粒材料也可能表现出类似于排水条件下液化的不稳定行为，通常称为扩散不稳定性，可以通过恒定剪切排水（CSD）测试来研究。迄今为止，对二元混合物中CSD的研究还不够。因此，利用离散元法（DEM）对CSD路径下的二元混合物进行了一系列数值试验。可能的不稳定模型分为I型和II型，I型不稳定发生在达到临界状态线（CSL）之前，而II型不稳定发生在超过CSL之后。该研究分析了宏观不稳定行为以及细含量（FC）对宏观不稳定行为的影响。数值结果表明，随着 FC 的增加，不稳定线 (IL) 的斜率首先增加，然后落在 p-q 平面内。在 e-p 平面中，IL 首先减小，然后上升。二元混合物的不稳定类型不仅受相对密度的影响，还受 FC 的影响。稳定性指标随着FC的增加先增加后减少。通过研究织物-应力关系来探索二元混合物不稳定性的微观根源。弱接触子网的崩溃会引发样本失稳，而强接触子网则决定了实现失稳的难度。 FC影响强和弱接触网络的织物各向异性的演化，从而控制二元混合物的宏观不稳定行为。