Monotonic and Cyclic Liquefaction of Very Loose Sands with High Silt Content

The results from an experimental study on sands with high nonplastic silt content are presented. Drained and undrained triaxial compression tests, undrained cyclic triaxial tests, and drained∕undrained instability tests were performed on specimens of loose Nevada sand with 40% silt content. The behavior was observed to be somewhat different from previously published tests with sands at lower silt content. The greater silt content appears to provide a more volumetrically contractive response throughout the entire stress-strain curve. However, some aspects of the response were similar to sands with lower silt content. Monotonic undrained tests indicated “reverse” behavior, i.e., static liquefaction occurred at low confining pressures and increasing dilatant volume-change tendency was observed with increasing confining pressure. Analyzing the results using the concepts of steady state resulted in a unique steady-state line only when undrained tests were sheared from the same isotropic compression line. When specimens of different initial densities were tested at the same initial confining pressures, the resulting steady-state points did not fall on the same steady-state line.