Riprap Protection of Vertical-Wall and Spill-Through Bridge Abutments

Scour around bridge abutments frequently leads to the collapse of bridge superstructures. Consequently, scour countermeasures are usually designed and installed by river engineers, riprap matting being the most widespread solution. The associated design criteria must attend to two groups of failure mechanisms: i) those associated the abutment body stability, which include particle erosion, translational slide failure, modified slump and slump failure; ii) those associated with the riprap apron stability, including shear, winnowing, edge failure, bed-form undermining and river bed degradation. The work presented in this communication consists on the review of design criteria recently published by the authors to face particle erosion, shear, winnowing and edge failure mechanisms at vertical-wall and spill-trough bridge abutments, under clear water flow conditions. These are the key aspects to be faced as soon as abutments are located in flood plains, their side slopes are not too steep and pore pressure is negligible. The work is based on a large experimental campaign carried out at several facilities and allows the specification of blocs’diameter, plan layout and thickness of riprap mattresses.