Evolution of scouring process downstream of grade-control structures under steady and unsteady flows

摘要

For many incised channels, one of the most common strategies is to install some hard structures, such as grade-control structuresn(GCSs), in the riverbed to resist further incision. In this study, a series of experiments, including both steady and unsteady flownconditions, were conducted to investigate the scouring process downstream of a GCS. Three distinct phases, including the initial,ndeveloping and equilibrium phases, during the evolution of scour holes were identified. In addition, a semi-empirical method wasnproposed to predict the equilibrium scour-hole profile for the scour countermeasure design. In general, the comparisons betweennthe experimental and simulated results are reasonably consistent. As the studies on temporal variation of the scour depth at GCSsncaused by floods are limited, the effect of flood hydrograph shapes on the scour downstream of GCSs without upstream sedimentnsupply was also investigated experimentally in this study. Based on the dimensional analysis and the concept of superposition, anmethodology is proposed to simulate the time evolution of the maximum scour depth downstream of a GCS for steady flows.nMoreover, the proposed scheme predicts reasonably well the temporal variations of the maximum scour depth for unsteady flowsnwith both single and multiple peak. Copyright © 2012 John Wiley & Sons, Ltd.