Undrained Seismic Compression of Unsaturated Sand

Unsaturated soils in engineered geostructures like embankments or retaining walls may experience seismic compression during earthquakes due to particle rearrangement associated with large-strain cyclic shearing. Although previous studies have investigated volume changes drained shearing of unsaturated soils, undrained presents a more complex situation. During shearing, total volume, matric suction, degree saturation, effective stress, shear modulus, and damping ratio occur that coupling effects affect compression. To better understand these effects, this study performed series simple tests on sand specimens. Contractile volumetric strain after 200 cycles was found vary nonlinearly saturation. The largest contraction occurred at saturation 0.4 coincided the decrease mean stress. specimens followed wetting-path scanning curve small suction. stress for all same linear relation accumulation strain.