Scour in Stone Beds Downstream Weirs and Compound Gates

Abstract

In the present investigation, a laboratory study of scour characteristics downstream weirs, compound gates has been conducted. The study included the measurement of maximum scour depth and the length of scour hole downstream these structures. Also, the effects of structure height, under sluice opening height, discharge variation and the diameter of bed material on the depth and length of scour hole. Two hundred and thirty four experiments were conducted in a concrete laboratory channel. Three sizes of crushed aggregate in range of (1.43-2.21)cm and three of gate height 15, 20 and 30cm were tested . Three heights of gate openings 1, 2 and 3cm were also tested. Experimental Results of this study showed a good direct relationships between relative scour depth (Ds/D50) and relative scour length (Ls/D50) with densimetric Froude number (Fro) for weirs and compound gates. It was also shown that (Ds/D50) and (Ls/D50) have good relationships with the relative discharge (qu/qd) for all cases and bed materials of compound gates. Two empirical relationships were obtained to estimated (Ds/D50) and (Ls/D50) in terms of (Fro) and relative water surface fall (ΔHw/P) for weirs with high determination coefficients. Another two empirical relationships were obtained to estimated (Ds/D50) and (Ls/D50) in terms of (Fro) , relative water surface fall (ΔHt/P) , relative opening height (h0/ΔHt) and relative discharge (qu/qd) for compound gates with high determination coefficients.