Development an empirical formula to calculate the scour depth at different shapes of non-uniform piers

Abstract

The study of local scour around foundation of bridge piers is very important for safe design of piers and other hydraulic structures. Various studies about local scour around uniform bridge piers but a few studied non-uniform bridge piers, Non-uniform bridge pier is one for which the cross-sectional dimension varies over the length of pier (piers with footings). In this study, the effect of main parameters (pier shapes, foundations shapes, level of foundation, flow intensity, and Froude number) on local scour with different shapes of non-uniform piers were experimentally investigated with five different velocities 0.16, 0.18, 0.21, 0.24, and 0.27) m/sec. The tests were occurred using laboratory flume, operated under the clear water condition using sand as a bed material. The test program was done on five different piers Rectangular, Chamfered, oblong, Octagonal, and Hexagonal, foundation shapes were rectangular, oblong, and hexagonal. The results showed that the rectangular pier with rectangular foundation gives the maximum scour depth about 6.5 cm when foundation is placed above bed level, while the hexagonal pier with hexagonal foundation gives the minimum scour depth 2 cm, when foundation is placed below bed level.