Undrained monotonic shear behaviour of loose sand-silt soil mixture

Abstract

ABSTRACT The undrained shear behaviour of sand-silt mixture is studied in the loose state using triaxial test. To this end, besides common physical tests, samples were prepared with silt contents as 0%, 10%, 20%, 40%, 60% and 80% and tested under 50, 100, 150 and 300 kPa confining pressures. Test results showed that minimum void ratio indexes were achieved for the mixture having 20% to 30% silt content. Presence of silt content up to 40% changes the soil stress-strain and pore water pressure-strain behaviour pattern and further increasing of silt content has no important effect on the soil mixture behaviour. Also, presence of silt particles between the sand grains increased the effective internal friction angle of soil at critical state. At the end, regardless of soil mixture, there is a linear relationship between the final excess pore water pressure and shear strength of soil, so that, shear strength of soil decreases with increasing of final excess pore water pressure.