Author(s): Haoran Wang
Keywords: Diversion tunnel; Robotic system; Hydraulic simulation; Structural assessment; Cracks;
Abstract: The structural health of the diversion tunnel is the basis of the production and operation of a hydropower station. Currently, the vast majority of the routine inspections are performed manually by operators, which could be subjective, unsafe, untimely, and inefficient. Furthermore, there are a certain number of inaccessible parts in the diversion tunnel system due to the complex structural layout and spatial characteristics. This study introduces a robotic system designed for inspecting concrete appearance defects of the diversion tunnel. Mobile robot ET-1, equipped with a millimetre-level CCD camera and the fill-light apparatus, can complete efficient image acquisition tasks in the humid, leaky, and light-absent conditions. Inspection operation by the robotic system was performed in the 2# tunnel of MRock hydropower station located in southwest China. The typical concrete defects such as scaling, cracking, spalling, pockmark, and leakage was comprehensively detected along the low-pressure headrace tunnel to the lower curved section. The results show that there is no significant damage to the upper headrace tunnel and inclined shaft, with no cavitation damage found in both bottoms and lateral walls. In terms of the defect types, cracks are the most widely distributed defects, which are usually associated with calcium leaching and leakage. The leakage occurring probability in the high-pressure headrace tunnel is less than the inclined shaft due to the lower water pressure distribution.