Scour investigation around single and two piers in side by side arrangement

Abstract

Laboratory experiments concerning scour development around single and two piers side by side arrangement have been conducted in order to provide a comparison of scour depths and patterns. The experiments are carried out under unidirectional currents of clearwater scour conditions. A variety of conditions including different flow depths, pier diameters and pier spacing are considered to have significant influence on the development of the potential scour hole. The research on local scour around single and two piers side by side arrangement are studied by using a 15.24 m long, 0.46 m wide and 0.4 m deep flume in the Hydraulics and Hydrology Laboratory, Universiti Teknologi Malaysia (UTM).Experimental results describing the scour-hole depths and patterns are discussed. The results show that the magnitude and extent of the scour depth depends directly on pier size, pier spacing and flow condition. Piers, which are larger in diameter, produced greater scour depth. It also shows that by increasing the pier spacing, the scour depth around two piers decreases and closes to values of single pier. The two piers act as an obstruction which disturbed the flow field and caused large turbulence levels to be generated. Thereby, a further increase in the scouring velocity is produced giving relatively higher scour depth values. The prime factors governing the local scouring process associated with piers are pier spacing, horseshoe vortex, reinforcing and sheltering. The results show that good agreement with previous study where the down flow causes of increased scour for a single pier case. Meanwhile, the horseshoe vortex appears to be the main cause of scour in the case of two piers side by side arrangement.