Experimental Study on Scour Around T-Head Groynes in Open Channel

Abstract

Groynes are the river training structures which are used extensively in anti-erosion activities. An experimental investigation of scouring around the groynes in an open channel is presented in this paper and an attempt to analyze the behavior of T-shaped groynes in terms of its applicability in alluvial channels was made. Tests were conducted by varying the symmetry of flange in three different manners (symmetric, larger flange in upstream and downstream respectively) and it is concluded that symmetrical groynes are more economical in terms of scour prevention and bank protection. When flange is more towards upstream direction of flow, it causes more turbulence in upstream and vice versa. For their suitability in upstream and downstream direction it is found that upper reaches of channel is more stabilized when the longer portion of flange is in downstream direction and downstream portion of channel is more stabilized when the flange is more towards upstream direction. Overall it is concluded that symmetrical T-shaped groynes are more efficient as compared to unsymmetrical forms. Further it is advantageous to use T-head groynes by using the suitable contraction ratio and length to space ratio between the adjacent groynes. In this study the contraction ratio (length/width) of 0.39 and spur ratio (spacing/length) of 5 was used.