Liquefaction of unsaturated soils- volume change and residual shear strength

This study presents a series of triaxial tests to highlight the effect of saturation degree ranging from 79.8% to 100% on the behavior of sand subjected to cyclic loading, the development of pore water pressure increment, the volumetric strain at liquefaction state, and the behavior of sand subjected to monotonic loading after liquefaction. The tested sand was Hostun RF sand, fine clear sand that has been widely used in laboratory testing in France. The results show that there is a difference between the behavior of samples having saturation degrees higher and lower than 95%. Besides, the development of pore water pressure increment is affected significantly by the value of cyclic stress ratio (CSR) and saturation degree. The Saturation degree also affects the appearance of criteria of liquefaction as Excess Pore-water Pressure (EPP) and Double Amplitude of axial strain (DA). The analysis of the effect of saturation degree on sample volumetric strain exhibits nonlinear liquefaction criteria for a given maximum value of CSR. The monotonic loading tests after liquefaction showed a small difference between the monotonic compressed behavior of the samples before and after liquefaction.