Relative Roles of Intergranular Friction & Fines on Undrained Behavior of Silty Sands
Sabanayagam Thevanayagam Principal Investigator
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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.<br/><br/>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.<br/><br/>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.