Abstract Many geological hazards such as landslide, liquefaction, slope failure and rockfall occur in mixed gravelly alluvium or colluvium deposits, highlighting the importance of studying gravel–sand–silt mixtures. Although many natural strata are built using these mixtures, they are not entirely understood. A fundamental experimental study was designed to explore the influence of non-plastic fine content on the undrained behavior of gravel-sand-silt mixtures as common geomaterials in nature. Undrained monotonic triaxial tests were carried out. Three types of sandy gravels with different sand-to-gravel ratios were selected as base gravels. The impacts of the non-plastic fine content on the stress–strain behavior, static liquefaction potential, steady sate line, residual strength and critical state friction angle were studied. The laboratory results show that both sand-to-gravel ratio and non-plastic fine content have significant impacts on the undrained response of gravelly mixtures. It was observed that mixtures with zero non-plastic fines content exhibit the non-flow liquefaction behavior. However, adding silt content up to 45% shows the limited liquefaction or flow behavior, depending on the base gravelly soils and fine content percentage. A threshold for non-plastic fine content was found to be 35%–45%. Below this threshold, the steady state line shifts downward as silt content increases, and then shifts upward with further increase in the silt contents. The identical trend was also noted for residual strength and critical state friction angle. For silt contents below the threshold, the equivalent intergranular void ratio concept (modified with a new logical assumption) was used to analyze the behavior of gravelly mixtures. The results clearly indicate that the accurate value of equivalent intergranular void ratio can fully explain the behavior of sandy gravel-fine mixtures, similar to sand-fine mixtures. From a microstructure perspective, both sand and silt content act as fine-grains in gravelly mixtures and should be considered when studying the mechanical properties of theses mixtures.

中文翻译：

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非塑性细粒对砂砾石静态液化和不排水单调行为的影响

摘要 混合砾石冲积层或崩积层沉积物中发生滑坡、液化、边坡失稳和落石等地质灾害，突出了研究砾石-砂-淤泥混合物的重要性。虽然许多天然地层是使用这些混合物建造的，但它们并没有被完全理解。设计了一项基础实验研究，以探讨非塑性细粒含量对作为自然界常见地质材料的砾石-砂-粉土混合物不排水行为的影响。进行了不排水单调三轴试验。选取三种不同砂砾比的砂砾石作为基砾石。研究了非塑性细粒含量对应力应变行为、静态液化势、稳态线、残余强度和临界状态摩擦角的影响。实验室结果表明，砂砾比和非塑性细粒含量对砾石混合物的不排水响应有显着影响。观察到具有零非塑性细粉含量的混合物表现出非流动液化行为。然而，添加高达 45% 的淤泥含量显示出有限的液化或流动行为，这取决于基础砾石土壤和细粒含量百分比。发现非塑料细粒含量的阈值为 35%–45%。低于此阈值，稳态线随着淤泥含量的增加而向下移动，然后随着淤泥含量的进一步增加而向上移动。残余强度和临界状态摩擦角也有相同的趋势。对于低于阈值的淤泥含量，等效粒间空隙率概念（用新的逻​​辑假设修改）用于分析砾石混合物的行为。结果清楚地表明，等效粒间空隙比的准确值可以充分解释砂砾-细混合料的行为，类似于砂-细混合料。从微观结构的角度来看，沙子和粉砂含量都作为砾石混合物中的细颗粒，在研究这些混合物的机械性能时应予以考虑。