Assessment of the correlation between grain angularity parameter and friction index of sand containing low plastic fines

Abstract

ABSTRACT This paper describes a fundamental research to explore the impact of grain angularity on theinstability and steady state friction angles of binary mixtures through laboratory triaxial compression tests performed on three different sands named as Chlef sand “CS”, Fontainebleau sand “FS” and Hostun sand “HS” mixed with low plastic Chlef silt in the range of Fc=0% to 30%. The silty sand samples were prepared with dry funnel pluviation and subjected to three different initial confining pressures (P’c=100 kPa, 200 kPa and 300 kPa). The obtained test results indicate that the low plastic fines content has a significant influence on the instability friction angle (φins), steady state friction angle (φss) and angularity ratio (Ar=Ahs/Amix) of the used materials. New proposed parameter named as friction index (FI= (φss- φins)/ φss) is suggested to evaluate the instability zone of the tested materials. Indeed, the friction index increases with the increase of fines content for the silty sand soils. Moreover, the obtained results demonstrate clearly that the instability and steady state friction angles could be correlated with the angularity ratio and friction index. The angularity ratio and friction index appear as appropriate parameters to identify the undrained instability zones of silty sand.