Riprap protection of vertical-wall bridge abutments

摘要

This study addresses the use of riprap as a countermeasure against scouring near vertical-wall bridge abutments under clear water flow conditions. It deals with the diameter of riprap, D_(r50), the layout of mattresses and their layer thickness, t. It aims to confirm existing criteria and to define appropriate formulations, whenever pertinent. Experiments were performed on a rectangular sand-bed open-channel, by imposing different abutment lengths and by choosing three riprap stone sizes. It became obvious that ⅰ) the stone size and mattress extent depend on the ratio between the abutment length and the flow depth and that ⅱ) winnowing can be avoided when the layer acts as a granular filter or the layer thickness exceeds 3D_(r50).