Local scour around closely placed bridge piers

Abstract

ABSTRACT Bridges situated close to each other show interference effect on scour depth around bridge elements as compared to the scour depth around isolated bridge elements. A number of investigations have been made in case of a single isolated pier having different shapes and flow conditions. But the investigations on bridges likely to interfere are relatively much lesser. Addressing the issue, an experimental study was conducted with circular and oblong piers of size, D = 6.2 cm forming tandem, side by side and staggered patterns. A recirculating flume 12 m long, 0.6 m wide and 0.7 m high with uniform sized sediment of average size, d5 0 = 0.23 mm was used for the experimental work. Experiments were run at a velocity equal to 0.93 times the critical velocity, uc. Piers when spaced from each other by a distance of one pier diameter showed maximum scour depths of 1.06, 1.51 and 1.53, respectively, for the tandem, side by side and staggered arrangements as compared to that of a single pier. However, when the inter- pier spacing was 16 times for tandem, two times for side by side and five times for staggered arrangements, the piers behaved independent of each other’s presence.