EVALUATION OF LOCAL SCOUR DEVELOPMENT AROUND PRISMATIC AND NON-PRISMATIC BRIDGE PIERS WITH DIFFERENT SHAPES

In this study, laboratory experiments were conducted to evaluate the local scour around piers. Effects of many parameters on the maximum depth of scour and scour pattern around piers have been studied. The study considered the effects of upstream flow conditions, shape of pier, side slope angles, and type of soil. Three cross sections for pier (circular, elliptical and oblong) were used for different velocities and discharges to find the scour depth. Two types of uniform cohesionless soil with median grain sizes of d50=0.25 (bed soil of Al-Kufa river), and d50=0.66 were used as bed material. Four angles of pier side slope were selected 0° (prismatic pier) and 5°, 10° and 15° (non-prismatic piers). It has been observed that for circular cross section pier, the maximum reduction for the scour depth at the upstream of the pier with a side slope of 15° for the soil of d50=0.25mm was about 63.64% and for the soil of d50=0.66mm was about 54.55%. The reduction value was increased up to 80% and 75% for the same angle of pier side slope (Ɵ=15°) with oblong cross section for the soil of d50=0.25mm and d50=0.66mm respectively