基于T-S模糊故障树的寒区水库大坝冻害风险分析

Frost damage risk analysis of reservoir dam in cold regions based on T-S fuzzy fault tree

由于运营环境恶劣,寒区水库大坝会面临冰冻灾害频发且致灾因素众多等问题,严重影响大坝稳定运营,增大了安全风险隐患,并增加了整治维修成本。为有效预防大坝冻害发生,提升大坝风险管理水平,提出了一种基于T-S模糊故障树理论的寒区水库大坝冻害风险分析方法。以坝体不均匀变形、坝体渗漏加剧、面板冻害破坏为下级事件建立了T-S模糊故障树;同时通过底事件重要度计算对主要致险因素进行了分析;并将冻胀力学分析与T-S模糊故障树相结合,对红旗泡水库大坝面临的冻害风险进行了计算分析。研究发现诱发大坝冻害的主要风险因素包括反复冻融作用,库区水位波动、冰层堆积与风浪侵蚀,面板与坝体填筑质量缺陷和坝体防渗及保温措施不足等;同时,发现红旗泡水库大坝发生冻害风险的可能性较高,应进行风险排查与处理。应用结果表明,所提出的方法能科学合理地分析大坝冻害风险并确定关键致险因子,可为寒区水库大坝的冻害风险的识别、管理与决策提供技术支持,进而为大坝设计、施工、运营维护及冻害防治提供参考依据。

Dams are important infrastructure with specific functions in reservoirs, widely used for flood control, irrigation, water supply, sediment control, improving ecological environment and solving uneven distribution of water resources, etc. More than 87 000 dams have been built in China in the last decade, of which more than 60% are located in cold regions. Due to the complex operating environment, reservoir dams in cold regions face the problems of frequent freezing disasters and many disaster-causing factors. Those problems seriously affect the normal operation of dams, increase the security risk and add the cost of renovation and maintenance. In order to effectively prevent the occurrence of dam frost damage and improve the level of dam risk management, a frost damage risk analysis method of reservoir dam in cold regions based on T-S fuzzy fault tree theory was proposed. The T-S fuzzy fault tree uses fuzzy numbers to describe the degree of failure and the probability of failure and replace the logic gates in the traditional fault tree with T-S fuzzy gates. The method not only can systematically sort out the dam frost damage failure events and perform reliability and safety calculations by logical deduction, but also takes into account the uncertainty and fuzziness of the probability of failure and solving the problem of the traditional fault tree based on the two-state assumption and relying on a large amount of failure probability data. In this paper, a T-S fuzzy fault tree was established with dam uneven deformation, dam leakage intensification, and panel frost damage as subordinate events. Then the main risk factors were analyzed by calculating the importance of the bottom event. At the same time, in order to exclude to the interference of subjective factors on the evaluation results of specific engineering risks, this paper tries to combine mechanical calculation and risk analysis to evaluate the actual engineering. The method combines frost swelling mechanics analysis and T-S fuzzy fault tree to calculate and analyze the risk of frost damage faced by the dam in Hongqipao Reservoir.Firstly, the relevant theories and methods of engineering mechanics and permafrost mechanics were used to analyze the frost damage problem faced by the dam in Hongqipao Reservoir. Then the calculation results were transformed into the bottom event fault degree substituted into the T-S fuzzy fault tree. Finally, the fuzzy possibility of the top event of frost risk was calculated and analyzed by the frost risk analysis process established in this paper. The study found that in the process of freezing risk control and decision making of reservoir dams in cold regions, the focus should be on repeated freezing-thawing action, wind and wave erosion, water level fluctuation and ice accumulation in the reservoir area, quality defects of the panel and dam filling, and insufficient anti-seepage and thermal insulation measures. It was also found that the frost damage risk of the dam in Hongqipao Reservoir is relatively high, and extra attention should be paid to the control and treatment of frost damage risk during operation and maintenance, and frost damage risk identification and maintenance based on the results of the importance of each bottom event analysis. The results of application show that the proposed method can scientifically analyze the risk of dam freezing damage and determine the key risk factors. This work can provide technical support for the risk identification, management and decision-making of freezing damage to reservoir dams in cold regions, and further it is useful for the design, construction, operation, maintenance and frost damage prevention of reservoir dam.