SCOUR INVESTIGATION AROUND SINGLE AND TWO PIERS SIDEBYSIDE ARRANGEMENT

Abstract

Laboratory experiments concerning scour development around single and two piers side by side arrangeme nt have been conducted in order to provide a comparison of scour depths and p atterns. The experiments are carried out under unid irectional currents of clearwater scour conditions. A variety of conditions inc luding different flow depths, pier diameters and pi er spacing are considered to have significant influence on the development of the pot ential scour hole. The research on local scour arou nd single and two piers side by side arrangement are studied by using a 15.24 m lon g, 0.46 m wide and 0.4 m deep flume in the Hydrauli cs and Hydrology Laboratory, Universiti Teknologi Malaysia (UTM).Exp erimental results describing the scour-hole depths and patterns are discussed. The results show that the magnitude and extent of t he scour depth depends directly on pier size, pier spacing and flow condition. Piers, which are larger in diameter, produced great er scour depth. It also shows that by increasing th e pier spacing, the scour depth around two piers decreases and closes to values of single pier. The two piers act as an obstruction wh ich disturbed the flow field and caused large turbulence levels to be generated. The reby, a further increase in the scouring velocity iproduced giving relatively higher scour depth values. The prime factors govern ing the local scouring process associated with pier s are pier spacing, horseshoe vortex, reinforcing and sheltering. The results sho w that good agreement with previous study where the down flow causes of increased scour for a single pier case. Meanwhile, the horses hoe vortex appears to be the main cause of scour in the case of two piers side by side arrangement.