Relative Roles of Intergranular Friction & Fines on Undrained Behavior of Silty Sands

液化砂土抗剪强度的合理选取是地震作用下边坡稳定性评价的重要组成部分。目前，确定抗剪强度的方法主要有三种：稳态强度法、剩余场强法和归一化强度比法。这些方法之间的基本主要差异对设计分析中剪切强度的适当选择提出了重大挑战。此外，许多破坏发生在粉砂而不是砂中。最近的勘探工作表明，粉质砂中的细粉导致的颗粒间接触的作用导致了几次观察到的失败。更好地理解粉质砂土中不同密度下细粒和粒间摩擦接触的相对作用将有助于制定一个一致的桑迪强度表征方法。本研究的目的是从根本上理解不同土壤密度水平下细粒和粒间摩擦接触对桑迪应力-应变-强度特性的相对作用。并描述这些不同作用在不同密度水平下的影响。实验室研究包括在不同细粒含量、密度和围压水平下不同级配的松散至中密非塑性粉质砂的单调和循环应力-应变-强度行为。基于本研究的结果，将发展建议粉质土的应力-应变-强度特性的液化和液化后的强度评估的目的，从本研究的结果将促进理解在天然土壤中的土壤基质的行为，并有助于发展的方法来表征土壤在地震荷载条件下的行为。 因此，它将有助于发展的液化潜力评估，液化后变形，和含有非塑性细粒天然土壤的流滑潜力分析的合理准则。

The appropriate choice of shear strength of liquefied sands is an important component in seismic slope stability evaluation. At present, shear strength is mostly determined by three methods: steady-state strength, residual field strength, or normalized strength ratio. Fundamental major differences between these methods pose significant challenges in the appropriate selection of shear strength for design analyses. In addition, many failures have occurred in silty sands rather than sands. Recent exploratory work suggests that the role of inter-granular contacts due to the fines in the silty sands contributed to several observed failures. A better understanding of the relative roles of fines and inter-granular contacts at different densities of a silty sand will help formulate a consistent method for strength characterization of sandy soils.The aim of this research study is to develop a fundamental understanding of the relative roles of fines and inter-granular frictional contacts at different soil density levels on the stress-strain-strength characteristics of sandy soils, and to delineate the effects of these different roles at different density levels. Laboratory studies include the monotonic and cyclic stress-strain-strength behavior of loose to medium dense non-plastic silty sands with different gradation at different fines contents, density, and confining stress levels. Based on the findings of this study, recommendations will be developed for stress-strain-strength characterization of silty soils for liquefaction and post-liquefaction strength evaluation purposes.The results from this study will advance the understanding of the soil matrix behavior in natural soils, and contribute to the development of methodologies to characterize soil behavior under earthquake loading conditions. Thus, it will help to develop rational guidelines for liquefaction potential evaluation, post-liquefaction deformation, and flow-slide potential analyses of natural soils containing non-plastic fines.