High-resolution sonars set to revolutionise bridge scour inspections

Abstract

As rainfall intensities increase so does the risk of scour damage to river crossings. Scour inspections are traditionally carried out by divers, but the water around bridge piers is often turbulent and murky such that little can be seen. This paper reports on a trial inspection of the underwater foundations of the 1889 River Hamble railway viaduct in Hampshire, UK using state-of-the-art high-resolution sonar and marine laser technologies. The trial was so successful it could transform the way such inspections are carried out in future. Three different sonar systems and a laser scanner produced a holistic assessment of the viaduct structure above and below the waterline. A three-dimensional record of all scour erosion features was digitally mapped along with the condition of the substructure. Significant scour was identified, contradictory to previous diver-based assessments. As discussed in the paper, sonar technologies can be rapidly deployed for emergency inspections as well as be immersed longer term for routine or periodic assessments.