Effect of non-plastic fines on undrained cyclic strength of silty sands

Whether the presence of silt adversely or beneficially affects liquefaction and the collapse potential of silty soils and how to evaluate cyclic strength behavior of a sand containing different silt contents are contentious issues. The purpose of this work is to investigate this question. Stress controlled undrained cyclic triaxial tests were conducted on specimen prepared by mixing a sand with silt in different proportions. The cyclic stress ratio (CSR=0.2) and confining pressure (100 kPa) were maintained constant. Relationship between no. of cycles required to cause liquefaction (at 5% axial strain) versus void ratio, and newly introduced equivalent void ratio indices based on intergrain contact density considerations are presented. Cyclic strength correlates well with the latter indices.