Hydrodynamic perspectives of soil scour in fluvial environment

Abstract

The major concern for many hydraulic structures is the effect of scour at the toe, when the racing floodwater scours away the bed just downstream of the piers. Therefore, understanding the soil-hydrodynamic interaction needs to be investigated. In this study, a series of 2D laboratory tests have been carried out to study the likelihood of soil scour due to the soil-hydrodynamic interaction and influence of sediment properties. Characteristics such as sediment deposition patterns, longitudinal/lateral spreading length/area, and bed scour profiles for three sediment diameters (i.e. 0.26, 0.30 and 2.40 mm) under dry and wet soil conditions are studied intensively. Experimental results revealed that soil of identical diameters under wet and dry conditions caused significant changes in soil scour rate and deposition patterns. Transport rates in dry condition were much slower than wet condition. It was observed that, for the same flow condition, different soils gave different long term equilibrium deposition patterns due to the grain size distribution and particle shape. Eddies were generated behind the soil samples which resulted in forming a series of ‘crescent’ zones. Findings of this study could offer a qualitative outline of the effects of various parameters to demonstrate a better representation of estimating scour rate in fluvial condition.