Effect of gravel fractions on direct shear strength of sand

Abstract: Naturally occurring and reconstituted granular soils consisting of a matrix of large and small particles i.e. quarry sand, backfills and saprolithic sands are encountered very often in construction. 100mm square shear box was used to determine the shear strength of 0.425mm – 9.5mm granular particles. The results reveal that for the size of shear box used, shear strength increases with average particles size up to 4.25mm and erratic for higher particle size. Addition of gravel results in decrease in dry density of the mixture and a decrease in mobilized strength. The Guth (1945) [1] Model is linear and predicted an increase in shear strength with gravel content in contrast with the laboratory values. The difference is due to the effect of rough textured gravel on the on the mobilized strength of the lower dry density matrix