【作者】 刘沛清；

【导师】 余常昭； 冬俊瑞；

【作者基本信息】 清华大学 ， 水力学及河流动力学， 1994， 博士

【摘要】 引用冲击射流的研究成果，详细地分析了在冲坑水垫内淹没斜向冲击射流的 扩散规律和各射流子区域内主要物理量的变化特征，并初步探讨了岩块的起动判 别条件。 利用瞬变流模型，探讨了岩缝内脉动压力波的传播规律和脉动上举力的成因， 导出可能最大脉动上举力的计算公式，并由三峡溢流坝断面模型冲坑底部不同尺 度岩块上的脉动上举力实验结果给出验证。 从岩块起动的动力方程着手，利用随机振动理论分析了岩块在脉动上举力作 用下的振动过程，并在岩块或板块的稳定性条件中引入了脉动上举力的频率响应 项，推求出平衡冲刷深度、平衡冲刷时间和冲刷深度发展过程等预报公式。同时为 了与理论分析成果相佐证，在三峡溢流坝断面模型冲坑底部，量测了不同尾水位下 岩块的起动过程，获得岩块振动频率、拔出时间、拔出速度和加速度等实验资料。 综合消能机理、射流扩散和随机振动等理论，给出估算平衡冲刷深度等预报公 式，并利用国内外若干挑流工程的原型观测和室内模拟资料，验证和推广了有关公 式。 利用有关研究成果对小湾工程的平衡冲刷深度给出预报，同时在该工程的断 面模型上用放大岩块法进行了系统的冲刷实验，且比较和分析了实验值与预报值。更多还原

【Abstract】 With main researched results of free impinging jets, the diffusive characteristics for an oblique-submerged turbulent impinging jet in a plunge pool and variations of main physical variables in the different jet sub-regions are analyzed in detail?and the lifting conditions for rock blocks in a scour pit are investigated preliminarily. By use of the model for transient flow, the mechanism of fluctuating pressure transmission in cracks of the bed rock and the cause of generating fluctuating uplift are investigated,and the predicting formula for the maximum fluctuating uplift is deduced. To confirm the theoretical results, the fluctuating uplift on variously dimensional rock blocks at the bottom of the scour pit are measured in the Three-Gorge spillway model.A ccording to the theory of random vibration, the process of random vibration for a rock block subjected to a fluctuating uplift is analyzed by the one-dimensional vibration equation and the frequency response term for a fluctuating uplift is introduced into the stability conditions of rock blocks or slabs. The predicting formulae for the limiting scour depth, the limiting scouring time and the development of scour depth are obtained theoretically. To verify above analytical results, the random vibration process for a rock block at the bottom of the scour pit is measured under different tail-water elevations in the Three-Gorge spillway model, and the vibrating frequency, the pulling out time, the pulling out velocity and acceleration for a rock block are obtained experimentally.Based on the dissipating mechanism in a plunge pool, diffusive characteristics of jets and the random vibration for a rock block, the predictng formulae for the limiting scour depth are presented, with the information of prototype and model for a number of hydroelectric power projects, the above formulae are confirmed and popularited. A AWith above main results, the Uniting scour depth for the Xiaowan project is predicted. Simultaneously, the scour experiment is carried out by the enlarged rock block method in the Xiaowan model, and experimental and predicted results are compared.更多还原