Influence of Suction History on Hydraulic and Stress-Strain Behavior of Unsaturated Soils

An experimental study was performed to investigate the effects of suction history on the hydraulic and stress-strain behavior of unsaturated soils. Test results show that, even if the same path of net stress and suction was followed during triaxial shearing, the stress-strain and strength behavior are different between specimens experiencing different suction histories. When the maximum suction experienced in the past was less than the residual suction, the specimen that experienced higher past suction produced higher shear strength. This is because the specimen was subjected to a higher suction, i.e., a higher average skeleton stress, and thus became overconsolidated. In contrast, when the maximum suction experienced in the past was higher than the residual suction, the specimen that experienced higher past suction produced lower shear strength. This is because, in this particular case, the high suction induced structural damage in the specimen, which impacts the stress-strain behavior during subsequent shearing. High suction greater than the residual suction was applied using the vapor equilibrium method by putting the soil sample in a glass desiccator with saturated salt solution. The wide suction history effects should be taken into account in constitutive modeling of unsaturated soils. (C) 2015 American Society of Civil Engineers.