Remotely Operated Robotic Drones for Inspection of Submerged Concrete Structures

The importance of periodic inspections for the assessment of the structural integrity and safety of civil infrastructure cannot be understated as they significantly reduce the risk of failure which could have enormous human, economic, and environmental consequences. Use of non-destructive testing (NDT) techniques are well documented on superstructures. In contrast, today, there are few commercially available techniques for quantitative NDT of submerged structures, which often operate in harsher environments. Conventionally, submerged structures are superficially inspected using visual testing by manned diving teams. However, divers are limited to shallow depths and face several risks, especially when visibility is poor, and space is constrained. This paper presents a first-of-its-kind quantitative NDT of submerged concrete structures using underwater remotely operated vehicles (ROVs) developed by Planys Technologies. These ROVs can be configured to inspect a wide range of applications including dams, bridges and jetties. In this study, widely used techniques, Schmidt/rebound hammer (RBH) and ultrasonic pulse velocity technique (UPV) have been engineered for use on submersible drones. Several challenges were addressed, including long-range communication and data acquisition, marinizing transducers and pulser-receivers. Planys’ ROV include high-definition cameras, lasers, sonar, and underwater positioning systems to improve data-acquisition quality and location tagging of defects. This allows us to collect a wider range of data, enabling tracking historical defect growth and estimating remaining life. This paper discusses the results from experimental studies conducted in a laboratory on prismatic concrete specimens. Furthermore, results from a successful field trial with details of the structure and operational procedure are described. Following calibration procedures, ROV based RBH and UPV tests were conducted systematically on the structure. Acquired data was subsequently used to characterize the interior of the structure and identify zones of potential local inhomogeneity. This work, while still in its early stages, is foundational to the development of a robust and reliable inspection method for monitoring the health of submerged concrete structures and will be of interest to asset owners in civil infrastructure, marine, water management and power generation industries.