Influence of drying/wetting cycles on the mechanical cyclic behaviours of silty clay

Abstract

To get a better understanding of the effect of drying/wetting cycles on the mechanical cyclic behaviours of silty clay, cyclic triaxial tests were performed on slurry consolidated silty clay specimens with various numbers of drying/wetting cycles, matric suctions, cyclic shear stresses and loading frequencies. Additionally, the soil microstructure before and after drying/wetting cycles was investigated with scanning electron microscope. The laboratory test results indicate that the threshold cyclic stress ratio and cyclic shear strength increased significantly at low matric suction due to drying/wetting cycles, with the changes becoming more gradual as matric suction continues to increase. The variation of mechanical cyclic behaviours is attributed to the irreversible compression, development of micro-cracks and lower degree of saturation. The overall influence of drying/wetting cycles depends on the weights of the three factors. For the specimens subjected to drying/wetting cycles, the cyclic shear strength increased with the increasing of loading frequency. Scanning electron micrographs show that soil particles were drawn closer together during the drying/wetting cycle process which led to variation of microstructure, resulting in alteration of the mechanical behaviours. The variation of the mechanical behaviours is consistent with the reconstruction of the soil microstructure.