Effect of non-plastic silt content on the liquefaction behavior of sand-silt mixture

To identify the effect of non-plastic silt on the cyclic behavior of sand-silt mixtures, total sixty undrained cyclic triaxial stress-control tests were carried out on sand-silt mixtures. These tests were conducted on specimens of size 71 mm diameter and 142 mm height with a frequency of 1 Hz. Specimens were prepared at a constant relative density and constant density approach. The effect of relative density, confining pressure as well as magnitude of cyclic loading was also studied. For a constant relative density (Dr=60%) the effect of limiting silt content, pore pressure response and cyclic strength was observed. The rate of generation of excess pore water pressure with respect to cycles of loading was found to initially increase with increase in silt content till the limiting silt content and thereafter it reverses its trend when the specimens were tested at a constant relative density. The cyclic resistance behavior was observed to be just opposite to the pore pressure response. Permeability, CRR and secant shear modulus decreased till limiting silt content; after that they became constant with increasing silt content.