Undrained Monotonic Pore Pressure Response of Saturated Silty Sand Soils

Abstract

The excess pore water pressure generated during earthquake shaking induces liquefaction and affects considerably the shear strength, shear stiffness, deformation, and settlement characteristics of soil deposits, and therefore the stability of the structures constructed from or founded on it. Published literature on the pore pressure generation characteristics and in turn the liquefaction resistance of sandy soils appears to be confusing. For the purpose of clarifying and evaluating the pore pressure generation characteristics of sandy soils, a series of undrained monotonic triaxial tests was carried out on different sand-silt mixture samples at various intergranular void ratios. The soil samples were tested under a constant confining pressure (σ 3 = 100 kPa) and two relative densities (D r = 20% and 91%). The results obtained from this study reveal that the fraction of low plastic fines plays an important role in the generation of the excess pore water pressure in Chlef sand-silt mixture samples. It was found that the excess water pressure increases linearly with the increase of the fines content and hyperbolically with the increase of the intergranular void ratio. The results show also that the gross void ratio parameter could not be used to represent the pore pressure response of the sand-silt mixtures and the excess pore pressure and the undrained shear strength at the peak can be correlated to the fines content up to 50%.