关键词: 三峡电站, 不同蜗壳埋设方式, 机组监测资料, 反馈分析, 结构承载规律

Abstract:

[Objective] The Three Gorges Hydropower Station is the only mega hydropower station in the world that employs three embedding methods of spiral cases. The operational conditions and differences among the units with these different embedding methods have attracted widespread attention. As the supporting system of hydroelectric generators, both the steel spiral cases and surrounding reinforced concrete structures have significant differences in construction processes and structural bearing characteristics due to different embedding methods. This study aims to comprehensively evaluate structural safety conditions, providing a basis for the safe operation of the power station and offering references for structural design and embedding method selection at other power stations. [Methods] Based on the monitoring data from the real-machine performance tests conducted during the experimental impoundment period of the Three Gorges Project, units with three types of spiral case embedding methods in the right-bank power plant were selected as the research subjects. The three-dimensional finite element method was used to conduct feedback comparative analysis of relevant monitoring parameters to summarize the structural bearing patterns and differences among different embedding methods of spiral cases. [Results] The finite element calculation results were consistent with the patterns of the monitored data, with close numerical values, validating the credibility of the monitoring results and the rationality of the design research and calculation methods. Under water pressure, the tensile stresses generated in both concrete and steel spiral cases were significantly greater in the circumferential direction than in the flow direction. The concrete bearing ratio of the direct embedding method was significantly higher than that of the other two schemes, while the stresses in concrete and steel spiral cases were generally at the same level in the pressure-maintaining and cushion methods. The concrete stress distribution in the direct embedding and pressure-maintaining methods was more uniform than in the cushion method. The stresses in the steel flow passage components, reinforcement bars, and the relative uplift displacement of lower frame foundation all remained within the design limits. The non-uniform uplift displacement of the lower frame foundation in the direct embedding method was notably greater than in other methods. Under thermal loading, concrete and steel spiral cases exhibited identical stress variation patterns. Tensile stresses developed during cooling and compressive stresses developed during heating. The stress in the flow direction was significantly greater than in the circumferential direction, and the magnitude of the stress increments was minimally affected by the spiral case embedding method. [Conclusions] Comprehensive analysis indicates that during the operation period, the structural concrete and steel components under all three embedding methods remain in the elastic stage of the materials, and the units are operating under the normal conditions anticipated in the design.

Key words: Three Gorges Hydropower Station, spiral case embedding, unit monitoring, feedback analysis, structural bearing