Armoring Effect on Local Scouring around the Bridge Pier under (Part1 :) Steady Flow

In this study armoring effect on local scouring around bridge pier under steady flow condition was
investigated based on model experimentation. Different combinations of bed-armor layers were
employed. Three circular piers of 22, 33 and 42 mm were used. Results show that while small bed
particles are under the protective effect of armor layer, increasing the total scouring depth, yields an
increase in the secondary armor layer depth until the armor layer itself is not influenced by the horseshoe
vortices. The minimum stabilized secondary armor layer is identical to the armor grain size.
Results showed that there is not meaningful correlation between total scouring depth and B/d (where B
is the pier diameter and d is the mean bed grain sizes) for B=33 and 42 mm. However for B=22 mm,
increasing B/d tends to increase the total scouring depth. For the armor layer particles size of 2.36 mm
the armoring effect for B=22 mm is vanished. The most important parameters in evolution of scouring
depth are the armor layer grain size and the armor layer thickness.