Experimental investigation of grain size effect on the temporal variation of local scour around bridge piers

Abstract

The soil grain size may affect the volume of scour-hole and maximum scour depth
substantially. In this paper, the effect of soil grain sizes (d50 = 3, 0.1, 0.002 mm) on the
temporal variation of local scour around bridge piers, circular in shape, is experimentally
investigated. The experiments were performed under clear-water scour conditions in a
rectangular flume at different Froude numbers, pier diameters and varying soil grain sizes.
Sieve analysis was conducted to determine grain sizes distribution of the studied soils and
find their d50 values. The scour test results showed that the grain size affects the volume of
scour-hole and maximum scour depth and plays a critical function in the scour process. The
results also illustrated that, in general, the equilibrium scour depths in the cohesive (or
clayey) soils is less than that in the non-cohesive (or sandy) soils.