Intergranular void ratio and undrained monotonic behavior of Chlef sand containing low plastic fines

Abstract

Stability analysis of soils prone to static liquefaction based on their monotonic undrained shear strength characteristics is an indispensable challenge in earthquake geotechnical engineering. This paper presents a laboratory study on the static behavior of Chlef sand–silt mixtures (with a silt content fc range from 0 to 50%); under low confining pressures. The experimental program includes undrained triaxial monotonic tests which were carried out for five types of samples, consolidated under different confining pressures (σʹc = 20, 50, 100, 150, and 200 kPa). On the samples preparation, the dry pluviation funnel has been used with a medium relative density (Dr = 60%). Main results obtained indicate that the fines content and initial confining pressure have a significant influence on instability stress and steady-state ratios of sand–silt mixtures. Moreover, the obtained data confirm the existence of a simple correlation between undrained instability stress, steady-state ratios, fines content, void ratios, and effective confining pressure. From the results obtained, nevertheless it can be concluded that the global void ratio does not represent the actual behavior of the soil under study, and the undrained residual strength decreases with a logarithmic manner with the increase of the intergranular void ratio, and a similar trend is occurring with the fine content of the sand–silt mixtures up to 50% as well.