| The safety of protecting structure in high dam plunge pool is the key to success or failure of energy dissipation. In recent years, a batch of high dams is under construction in China. The problem of energy dissipation is critical, and it is also the problem that needs to be solved in practice. The basic criterion of safety for the protecting structure is analyzed in this dissertation from the similarity law, material property, test method, the cause of hydrodynamic load, layout of model etc.. Based on the study of plunge pool in Xiluodu, Laxiwa, Jinping, Nuozhadu, Xiangjiaba projects, the predicting method of load and the stability analysis method of counter-arch slab are proposed by the synchronous measure of hydraulic parameters. Fore more the controlling factor and safety evaluating system of protecting structure are studied. The main achievements of this dissertation include as follows:The similitude condition of the flow in gaps between apron slabs is derived. The basic principle is proposed, which is used to study the stability of the plunge pool slab in the model test. The empirical formulas of the load acting on the flat slab and counter-arch slab that put forward in the paper can be used to evaluate the stability and to determine protecting range and protecting standard. Using the concept of "random arch", a mechanical analysis model of the counter-arch slab is developed and a physical model is built up to verify the analysis model at the same time. From the aspect of limit balance, the quantified safety index for the comparison between the counter-arch slab and the flat slab in stability is carried out. In terms of the stability of whole structure, the central angle of counter-arch structure is appropriate in the range from 30°to 70°. But when it refers to local stability, the ratio of central angel between single slab and the whole counter-arch structure will be suitable under 0.2. On the basis of structure characteristic of counter-arch slab, a new method to analyze the stability of counter-arch slab by using non-continuous numerical method is advanced. The calculating result by using this new kind of numerical method named block-spring is satisfactory. Based on a large number of test data, the quantified relationship between the impact pressure and the uplift on slab is described as well as the relationship between fluctuating pressure and impact pressure. The root mean square of fluctuating pressure is recommended as the control factor in this paper. The characteristics of the uplift acting on the slab in stilling basin are studied, and the predictive method is put forward. The fluctuating pressure as the parameter of safety control factor is suggested. The test data indicates that time-average pressure appears to be unfavorable characteristics to stability on the whole slab. The fluctuating pressure plays the main effect to the slab stable. The fluctuating pressure can express the maximum uplift that can be used as the safety control factor for evaluating stability of the slab. The hydrodynamic load acting on the lining structure on the slope increases with the declination of the water depth in plunge pool, and the fluctuating pressure on the bottom is larger than that of above. The fluctuating pressures on the slab and slope are almost equal in magnitude, and its positions of peak value are approximately the same. The proportion of time-average value in whole load is large. The relationship between maximum uplift and fluctuating pressure can be used as the factor of safety control. Based on the hydraulic model experiment of the guide wall in stilling basin of a large engineering project, relating to the calculation of dynamic finite element,the main conclusions can be gained as follows:The distribution of fluctuating pressure declines along the distance and the peak value occurs at the front of jump. The distribution of integer load acting on the guide wall is the same with fluctuating pressure. The transfer coefficient of point-area fluctuating pressure on both sides of...
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