Scour Hole Development in Natural Cohesive Bed Sediment around Cylinder-Shaped Piers Subjected to Varying Sequential Flow Events

Abstract

Scour evolution and propagation around a cylinder in natural cohesive sediment was uniquely investigated under multi-flow event varying sequentially by velocity magnitudes. This flume study differs from others that only used test sediment with commercially available clays for single flow. The objective of this study was to explore the potential differences in scour hole development in natural riverbed sediments subjected to varying flow velocity scenarios, advancing our understanding from existing studies on scour. The study consisted of 18 experimental runs based on: velocity, flow duration, and soil bulk density. Scour hole development progressed initially along the cylinder sides, and maximum depths also occurred at these lateral locations. Scour hole depths were less for higher soil bulk densities (≥1.81 g/cm3) compared with lower densities, and erosion rates were slower. It was observed with all flow sequences that scour depths were similar at the end of each experimental run. However, scour initiation was observed to be time dependent for soils with higher bulk density (1.81–2.04 g/cm3) regardless of flow velocity sequences. The observed time dependency suggests a process feedback with the scour hole development initiated at the cylinder sides, which influence local 3D hydraulics as the scour hole depth progresses.

Clear Water Scour at Varied Pile-Cap Elevation and Skewed Bridge Piers

“…Experimental studies were conducted on scour around complex bridge piers of various configurations to determine the effect of pile-cap thickness on the variation of maximum scour depth [18]. Research focusing on the relationship between the depth of scour in complex pier groups, combined pile bridges, and different parameters, such as variations in inflow velocity, distance, and duration, was provided [19]. An experimental evaluation was conducted on three complex bridge pier models (rectangular with rounded ends) under steady-state, clear-water flow conditions.…”