Non-contact measurement method for reconstructing three-dimensional scour depth field based on binocular vision technology in laboratory

Abstract

The scour of pile foundations significantly impacts the bridge structure safety. This study proposes a three-dimensional (3D) non-contact scour pit depth measurement method. Cameras were calibrated using a three-step calibration procedure based on the diagonal length. Refraction errors caused by the interface between water and air were corrected. The corresponding solutions are given to the problem that it is difficult to mark sand with traditional speckles, and the measurement range of a single camera is limited. The matching of virtual grid points between different views at different moments was achieved using the theory of digital image correlation (DIC) based on zero-mean normalized cross-correlation (ZNCC). The scour pit was reconstructed by splicing the depth field from different views. The comparison between the results of direct and visual measurements at a single point proves that the difference between them was basically at the millimeter level. Scour pits of different water depths, velocities, reciprocating flows, and unidirectional flows were photographed and reconstructed. Based on these results, the development of scour pits under various flow conditions is discussed.