Undrained shear strength of sand-silt mixture: Effect of intergranular void ratio and other parameters

Abstract

The determination of the appropriate undrained residual shear strength of silty sands soils that are prone to liquefaction to be used in the assessment of the post-liquefaction stability of different types of earth structures is becoming a major challenge.The objective of this laboratory investigation is to study the effect of intergranular void ratio on undrained residual shear strength of loose, medium dense and dense (Dr = 12, 50, and 90% before consolidation) sand-silt mixtures under monotonic loading and liquefaction potential under cyclic loading. For this purpose, a series of undrained monotonic triaxial tests were carried out on reconstituted saturated silty sand samples with fine contents ranging from 0 to 50%. The confining pressure was kept constant to 100 kPa in all tests. The results of undrained monotonic tests indicate that the global void ratio does not represent the actual behaviour of the soil and the undrained residual shear strength decreases linearly with the increase of the intergranular void ratio and similar trend is happening with the fine content of the sand-silt mixtures up to 50% as well. Undrained cyclic test results show that the increase of the intergranular void ratio and the fine content accelerate the liquefaction phenomenon for the stress ratio under study and the liquefaction resistance decreases with the increase of the intergranular void ratio and the loading amplitude.