| Abstract: | When gravel bed load deposits are sluiced from hydraulic structures, the mo- tion of bed load over the apron, as is well known, may consist of sliding, rolling and saltation. At times, saltation may become so intensive that gravels have been observed to jump clear out of the water surface. The movement of gravel bed load may cause serious damages to the hydraulic structures through abrasion and im- pact. The extent of damage depends upon a number of factors, such as rock prop- erties of gravels, flow conditions, configuration as well as the strength of materials of hydraulic structures. In most cases the movement of gravel bed load takes place in ribbons in plan, consequently, the lateral distribution of damages is uneven, and protective measures to be adopted against abrasion and impact should be applied to the key part most frequently attacked by the gravel bed load. Possible repair should be anticipated in the layout of structures in order to facilitate the operation. |
