Robotic Ultrasonic Pulse Velocimetry for Submerged Concrete Assets

Abstract

Concrete structures play a vital role in civil, commercial, and industrial projects. Periodic inspections are mandatory to ensure the safety and reliability of the asset throughout their lifespan. Recently, advancements in inspection technology have allowed for rapid and accurate assessment. Techniques ranging from ground penetrating radar to phased array ultrasonic tomography have made it possible to rapidly analyse the interior of concrete structures. Conventionally, inspecting concrete structures underwater is done visually by manned diving teams. Internal defects are often undetected in visual inspection. Furthermore, manual inspection underwater is often challenging owing to limited visibility, water currents, and debris, making it risky for divers to conduct inspections manually. However, as of date, there are no commercially available quantitative non-destructive techniques (NDT) to inspect submerged concrete assets. We have also observed no research adopting existing techniques for underwater applications. To address this need, this paper proposes the use of remotely operated underwater vehicles (ROVs) to adopt conventional ultrasonic pulse velocity (UPV) technique for underwater applications. ROV-UPV can identify zones of inhomogeneity within the concrete structure. The paper further discusses how factors like water saturation, marine growth, and the inspection surface affect the pulse velocity. Experimental studies conducted in the laboratory and in the field are discussed. Limitations of ROV UPV in practical scenarios are briefly discussed. This work will be of relevance to waterways managers, dam or reservoir engineers, and bridge management authorities.