Undrained Response and Liquefaction Resistance of Sand–Silt Mixtures

A series of undrained cyclic triaxial tests were performed on sand–silt mixtures, prepared after addition of non-plastic fines (in the range of 0–40%) into the fine sand. The cylindrical samples were prepared at medium dense condition (D_r = 50%) and saturated by purging CO₂ and application of back and cell pressures alternatively until the pore pressure coefficient becomes about 0.98 to 1.0. The samples were consolidated at 100 kPa pressure before cyclic load application. Each consolidated sample was then subjected to cyclic loading with the sinusoidal waveform at a frequency of 1 Hz. The cyclic loads were varied with CSRs in the range of 0.127–0.178 to obtain the resistance curves and assess the liquefaction resistance of sand–silt mixtures. This paper presents the pore pressure build-up, axial strain variation with load cycles and resistance curves to study the effect of cyclic load amplitude levels, over-consolidation, cycles of preloading and non-plastic fines on liquefaction resistance of fine sands. Test results indicate that, at constant relative density, the liquefaction resistance of fine sand decreases with the addition of non-plastic fines up to 40%. It is also noted that the liquefaction resistance of sand is increased substantially with an increase in cycles of preloading and over-consolidation pressures.