Experimental study of local scour around inclined bridge pier groups based on capped piles in presence of debris accumulation

In this paper, the effects of debris dimensions, pile cape thickness and installation levels, array and diameter piles on the maximum scour depth around inclined bridge pier groups were investigated experimentally. The bridge pier consist of two rectangular piers with 2.5 and 3.5 cm dimensions which mounted at an angle of 28 degrees on a pile cap with 10 cm width, 16 cm length, 3 and 5cm thickness which placed on an array of 2×2 and 2×3 piles with different diameters. The experiments were performed for relative flow depth (y/D) 6.42, 7.85, relative pile cap levels (Z/Tpc) 0, 1, 1.5, relative debris width and 2.85 and length 2, the relative thickness 0.85 and 1.42, in clear water conditions. Comparison of results proved that the effect of increasing flow depth has no significant effect on maximum scour depth. Results that in presence of the debris for pile cap relative level Z/Tpc=0, the maximum scour depth increases about 8.5% in comparison with no debris. For pile cap relative level Z/Tpc=1 presence of the debris increases the maximum scour depth up to 4.5% compared to no debris. By increasing the pile cap relative level to 1.5, presence of the debris causes an increase in the maximum scour depth about 4% in comparison with no debris