Strength Changes in Sand Following Cyclic Shear
Static torsional simple shear tests were performed on poorly graded sand, with and without prior cyclic loading, to evaluate changes in static shear strength. Specimens were prepared at three densities (loose, medium, and dense) and were subjected to one of three levels of cyclic loading corresponding to 0.25, 0.50, or 0.75 times the static stress level, causing failure with no prior cyclic loading. The test results indicate that post-cyclic shear strength increases in specimens that are contractive and decreases in specimens that are dilative during cyclic loading. Results showing the change in friction angle as a function of initial density and level of prior cyclic loading are presented. The observed behavior is consistent with a model that predicts strength changes following cyclic loading as a function of soil volume change characteristics and drainage conditions.