Voids Imaging on Underwater Concrete Slabs Based on Guide Wave Transmission and Distributed Transducer Network

Abstract

For the construction and maintenance of bridges, dams, pipelines, etc., the damage detection method of underwater concrete components is increasingly important to ensure the safety and reliability of civil infrastructures. Current visual and sonar techniques are not robust and sensitive for inspecting underwater concrete components, especially in low illumination and muddy water. Therefore, this paper proposes an ultrasonic method to detect underwater concrete voids besides traditional methods. First, theoretical derivation reveals the wave modes propagating at the water-concrete interface as well as the wave velocities. Second, finite element simulation is used to investigate the wave transmission through a void. Rayleigh waves are more reliable and sensitive to characterize underwater voids than bulk and Scholte waves. Third, a damage index is formulated considering the energy attenuation of the transmission of Rayleigh waves. The interaction of abnormal wave paths indicates the void in a damage image. Finally, a distributed transducer network is developed in experiments to image the concrete slabs with single and double voids underwater. The proposed method can enrich the nondestructive testing of underwater structures and ensure the safety of civil infrastructures.