Effects of Locations of Spur Dyke on Bed and Scour around Bridge Piers in Meandering Channel

Abstract

Spur dykes are the structures which are used to protect the eroding bank of rivers. They are sometimes also used to safeguard the life of many structures such as bridge piers, abutments etc. The efficiency of spur dykes has been checked in straight channels by conducting model tests in laboratories by many investigators. Very few studies were done in curved channels. In present work an attempt has been made to study the effect of location of spur dyke on bed and scour around bridge pier in curved open channel (bend angle = 80o ) with time. Experiment has been carried out in 80o channel bend at constant discharge (3.5×10–3 m3 /s) and bridge pier is located at angular displacement ϴ = 60o . Here ϴ is the angle the line drawn at the inlet of any bend to the line joining the centre of curvature and any point on the outer portion of the bend. It is found that maximum scouring occurs at ϴ = 0o and 20o along inner wall and at ϴ = 60o and 80o along outer wall. It is also found that scouring around bridge pier is more in the vicinity of pier and decreases with increase in distance from pier. The most suitable location for spur dyke to protect bridge pier is at angular displacement ϴ = 20o . Scour developed rapidly during initial time and then rate of scouring decreases with elapse of time.