Abstract
Scour is the main cause of failure for spur dike. The accurate prediction of scour around spur dike is essential to design a spur dike. The present study focuses on the maximum scour depth in equilibrium condition and parameters, which influence it in a sand–gravel mixture bed. Outcomes of the present experimental study showed that the non-dimensional maximum equilibrium scour depth increases with critical velocity ratio (U/Uca), water depth-armour particle ratio (h/da), Froude number for sediment mixture (Frsm), water depth-spur dike length ratio (h/l), and decreases with increase in armour particle-spur dike length ratio (da/l). The maximum scour depth is proportional to dimensionless parameters of U/Uca, h/da, Frsm, h/l, but the scour depth is inverse proportional to da/l. Scour around spur dike in a sand–gravel mixture is mainly influenced by the property of the sediment mixture. The scour increases with decrease in non-uniformity of the sediment mixture. A non-linear empirical equation is proposed to estimate the maximum scour depth at an upstream nose of rectangular spur dike with a maximum error of 15%. The sensitivity analysis indicates that the maximum non-dimensional equilibrium scour depth depends on Frsm, followed by the secondary sensible parameters da/l, h/l, and h/da.
Highlights
Spur dike is a manmade hydraulic structure, which is known as groin and spur
The scour progress ends in a sand–gravel mixture when a stable armour layer forms around the spur dike
Maximum scour depth at this condition is well-known as maximum equilibrium scour depth or maximum scour depth
Summary
Spur dike is a manmade hydraulic structure, which is known as groin and spur. A spur dike protects the stream banks by reducing the flow velocity against the fluvial hydraulic processes. Spur dikes are fixed in vertical/perpendicular, declined or inclined positions to the longitudinal direction of the stream. The present study only focuses on the rectangular vertical spur dikes, which are fixed perpendicular to the flow. Spur dikes are identified as an effective hydraulic structure to reduce the flow velocity for river bank protection [1,2,3]. After fixing a spur dike, the flow processes in the stream are different to disturb the flow characteristics. The scour study around the spur dikes is important for river engineering to provide practical guidelines [4]
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