Key technologies and application practice for intelligent inspection and safety evaluation of high arch dam stilling basin in complex underwater environment

The stilling basin serves as the key flood discharge and energy dissipation structure of high arch dams, which requires regular inspection to guarantee its structural health and stability. Underwater inspection stands as a vital instrument for safety inspection and health diagnosis of underwater structures in water conservancy and hydropower projects. By integrating acoustics, optics, and image recognition technologies, the current study developed the census-detail-refine inspection concept. Accordingly, this study proposed an intelligent inspection method of high arch dams that incorporates multi-beam underwater three-dimensional (3D) sonar detection, unmanned underwater vehicle system, floating-climbing dual-mode underwater inspection, and 3D laser scanning. By using this method, precise water depth data and point information for the target area were acquired. Additionally, high-precision images were generated to depict the attributes of the plunge pond floor. This approach allows for the efficient collection, identification, and health diagnosis of concrete floor defects in complex underwater environments, which effectively overcomes the shortcomings of traditional manual inspection such as high safety risks, limited diving depth, and insufficient detection accuracy. Based on the practical applications in the stilling basin project of Baihetan Hydropower Station, the field results indicate that the detection results of this method are reasonable and reliable. This method helps to further improve the automation, intelligence, and efficiency of underwater inspection operations in hydropower projects, and provides a guide for intelligent inspections of similar underwater hydraulic structures. These results can support the upgrading of inspection technology and the improvement of safety management level in the industry.