Long term cyclic behavior of unsaturated granular soils

Abstract

Abstract The road base and subbase materials are normally situated in unsaturated conditions, and are subject to traffic loadings over a long period of time. To study the influences of matric suction on the long-term deformation of road base and subbase materials, the large-scale cyclic tri-axial apparatus, equipped with unsaturated system, was adopted to conduct tests on these unsaturated coarse granular materials. Four matric suction and three cyclic stress amplitudes were applied on the specimens through the apparatus. The axis-translation technique was used to control the matric suction in the specimen. The test results indicate that with the increase of matric suction, the axial accumulated strain decreases at the declining rate, and larger cyclic stress amplitude will strengthen the influence of matric suction. An improved cyclic model containing a new exponential function to describe the influence of matric suction was then proposed. By comparing the experimental results and the calculated results, the improved model was validated to be effective to predict the long-term deformation of unsaturated granular soils.