Effects of Superimposing Cyclic Shear Stress on the Undrained Behavior of Saturated Sand Under Monotonic Loading

Abstract

The effects of superimposing cyclic shear stress on the undrained behavior of saturated sand under monotonic loading are identified and discussed. This stress-controlled cyclic shear stress is intended to represent the small seismic shaking persisting after the main strong shaking of an earthquake. It is characterized by the cyclic stress ratio and the number of cycles applied per 1% of shear strain developed by the sand along the direction of the strain-controlled monotonic load. The experimental program includes tests performed using bidirectional simple shear and hollow cylindrical torsional shear types of apparatus. The only material employed in this study is standard Japanese Toyoura sand. In both apparatus, the complementary cyclic stress is applied through and independent of the monotonic load. One of the most remarkable effects is the reduction of the strength attained by saturated sand under monotonic loading application alone.