Shear wave velocity in sand: effect of grain shape

Abstract

Whether the shear wave velocity in sand is dependent on grain shape is a basic question of considerable interest, yet remains open owing to the lack of solid experimental evidence. This technical note presents results from an experimental study where the effect of grain shape was carefully isolated from other factors and the grain shape was accurately measured using laser scanning technology. It is shown that, under otherwise similar conditions, shear wave velocity or the associated small-strain stiffness tends to decrease as sand grains become rounded, and that a fairly good correlation exists between stiffness parameters and a shape index known as overall regularity that accounts for grain shape in a collective manner. The study suggests that the laboratory finding reported in the literature, that a decrease in roundness of sand grains leads to a decrease in shear wave velocity or stiffness, was most likely attributable to varying gradation of tested materials rather than to varying grain shape.