《Table 2Table showing%difference of scour characteristics between circular and oblong piers》

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《受渗流影响的冲积河道中圆型和矩形桥墩受腐蚀情况和流动特性比较（英文）》

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In this study，two types of piers were used，i.e.circular and oblong piers.Diameters of circular pier was 75 mm；whereas，oblong pier of width 75 mm，length 225 and 270 mm were used.Height of piers was 150 mm.The sizes of piers were selected in such a way that width of pier should not be greater than 10%of channel width to avoid side wall effect on scour depth（Chiew and Melville 1987）.The bed slope was fixed at0.05%.First the sand bed was prepared plane throughout the channel.Thickness of sand bed was 17 cm in all experimental runs.Then piers were installed at 7.5 m，i.e.at centre of the test section of 5 to 10 m from downstream end of flume in such a way that the approach length ought to fulfil the fully developed flow condition.As riverbed are comprising of nonuniform sediment particles（Wu et al.2004），the experiments were carried out in the sand bed made up of non-uniform sand of median size（d50）0.5 mm.The geometric standard deviation（σg）for selected sand is 1.65，i.e.greater than 1.4 which confirms non-uniformity of sand（Marsh et al.2004）.Further，as far as the flow is concerned，considering to the fact that the aspect ratios were greater than 6，the flows in the experiments were free from 3D（three dimensional）effect provided by the side-walls（Yang et al.2004）.Experiments were conducted for three different discharges and for each discharge 10%seepage and 15%seepage were applied.Experimental runs were conducted for 24 h.Experimental conditions for present study are shown in Table 1.