Research On Safe Operation Monitoring Of High Dam Discharge Structure

In recent years,the water head of high dams and other discharge structures has been continuously increasing,and high-speed discharge will have adverse effects on the structure,leading to its overall damage in serious cases.Therefore,it is of great significance to monitor the operation state of high dams and other discharge structures.The vibration signal is an effective carrier reflecting structural vibration characteristic information.The signal processing and analysis can effectively extract structural vibration characteristic information,thus monitoring the operation states of structures.Taking the 5th overflow section of Three Gorge dam as the research object,the vibration characteristics of the dam is analyzed by using the prototype test data,characteristic information extraction and multi-point information fusion technologies.The dynamic sensitive factors reflecting the dynamic change process of the structural operation state are extracted,which are combined with the static sensitive factors such as statistical indicators to monitor the dynamic change process of the dam and evaluate its safety state.The main research contents of this paper are as follows:(1)Operating characteristic information extraction of the dam.The vibration signals of high dams and other discharge structures usually contain a large number of interference signals,mainly water flow noise and high-frequency white noise.The effective information reflecting the vibration characteristics of structures will be covered by interference signals,which will have a great impact on the safety evaluation accuracy of structures.To solve this problem,a novel de-noising method combining improved VMD and SVD is proposed to preprocess the vibration information of dam,filter out low-frequency water flow noise and high-frequency white noise,and extract the real vibration characteristics of structures.In order to evaluate the applicability and effectiveness of the IVMD-SVD method,we compare the de-noising results of simulation signals produced by IVMD-SVD with those produced by digital filter,wavelet threshold,empirical mode decomposition(EMD),empirical wavelet transform(EWT),singular value decomposition(SVD)and VMD methods respectively,and find a better performance of IVMD-SVD method.Furthermore,the proposed method is applied to the 5th overflow section of Three Gorges dam and the results show that IVMD-SVD method can accurately extract the operating characteristic information and analyze the dominant frequencies of the dam,which contributes to safety monitoring and evaluation of discharge structures.(2)Multi-point vibration characteristic information fusion is used to extract the overall vibration characteristics of the dam.The vibration signals are greatly affected by the location of measured points because of the complex working conditions of discharge structures.The single-channel signal has difficulties to reveal the overall operation feature of structures.A multi-point information fusion method based on variance dedication rate is proposed,and the method is applied to prototype test data of the 5th overflow section.The analysis results show that variance dedication rate method can effectively extract the overall vibration characteristics,and highlight the dominant frequencies of structures with strong engineering practicability.(3)Online monitoring of dam operation conditions.Permutation entropy is recommended as the dynamic monitoring indicator to monitor the dynamic change process of the dam.Statistical indicators such as 3? rule and coefficient of variation are used to quantitatively judge the operation condition of the dam,so as to avoid the limitation of dynamic monitoring indicators and improve the accuracy of online safety monitoring.The 5th overflow section of Three Gorges dam is taken as the research object to evaluate its safety and the impact of the dam on humans.The results show that permutation entropy as a dynamic sensitive factor can reflect the operation conditions of the dam at different moments,and monitor the operation conditions of discharge structures online.The maximum dynamic displacement of the dam under discharge condition is less than the allowable amplitude.The 5th overflow section is in a safe and stable operation state,and humans will not feel uncomfortable.