大坝溢洪道岩石冲刷数值模拟研究

发布时间：2018-09-12 21:28

【摘要】：溢洪道自由射流或者汛期大坝漫流引起的高速水流,能够对河床岩体造成严重冲刷,增大了坝基损坏的风险。国内外对高速水流的特性和冲坑形成过程进行了较多的研究,但对实际上广泛存在的以基岩或破碎基岩为主的溢洪道岩石冲刷数值模拟研究很少。本文提出了一种模拟河床岩石冲刷破坏的数值模拟方法,结合流体动力学和岩石力学理论,对溢洪道岩石冲刷进行数值模拟研究。主要研究内容及成果包括： (1)基于基岩冲刷理论和基岩的抗冲特性及分类,总结前人关于冲坑形成过程的概化模型。根据淹没射流理论,结合挑流消能特点,提出冲刷过程中基岩解体破坏的主要原因是：存在节理裂隙的河床岩体,经过具有强烈脉动的高速射流的直接冲击和泄流引起的脉动水压力共同作用的结果。 (2)阐述离散单元法理论及其在岩土力学中的应用,介绍离散单元法的基本思想和基本方程,探讨离散单元法作为一种处理节理岩体的数值方法的优越性。介绍通用离散单元法程序UDEC在岩石力学数值模拟中的应用,分析UDEC的模拟方法和特点,总结UDEC模拟基岩冲刷的可行性。 (3)基于流体动力学和岩体力学理论,提出一种模拟河床岩石冲刷破坏的数值模拟方法,即将水流冲击时均压力和脉动压力与岩体力学模型耦合,实现河床基岩冲刷过程的数值模拟。 (4)建立河床岩体冲刷的力学模型,在通用离散元程序UDEC中建立节理岩体的二维模型,加载裂隙水压力、挑射冲击水流时均压力和脉动压力,验证节理岩体在挑射水流作用下的解体破坏模型。模型中明显可见岩体节理的失效、岩块破碎及块移动等动态响应过程。 (5)研究动力荷载的变化对冲刷的影响。通过改变加载的正弦应力波的频率和峰值应力,研究岩石力学模型动态响应的区别。
[Abstract]:The free jet of spillway or the high speed flow caused by dam overflowing in flood season can cause serious scour to the rock mass of river bed and increase the risk of dam foundation damage. The characteristics of high velocity flow and the formation process of scour pits have been studied at home and abroad, but the numerical simulation of spillway rocks with bedrock or broken bedrock is seldom studied. In this paper, a numerical simulation method is proposed to simulate the erosion failure of rock in the river bed. Combined with the theory of fluid dynamics and rock mechanics, the numerical simulation of rock scour in spillway is carried out. The main research contents and results are as follows: (1) based on the theory of bedrock erosion and the characteristics and classification of bedrock scour resistance, the previous generalizable models of scour formation process are summarized. According to the theory of submerged jet and combined with the characteristics of energy dissipation, the main causes of bedrock disintegration and destruction during scouring are put forward as follows: the rock mass of river bed with joints and fissures exists. Through the direct impact of high speed jet with strong pulsation and the result of pulsating water pressure caused by discharge. (2) the theory of discrete element method and its application in geotechnical mechanics are expounded. This paper introduces the basic idea and equation of discrete element method, and discusses the superiority of discrete element method as a numerical method for dealing with jointed rock mass. The application of general discrete element method (UDEC) program in numerical simulation of rock mechanics is introduced. The simulation method and characteristics of UDEC are analyzed, and the feasibility of simulating erosion of bedrock by UDEC is summarized. (3) based on the theory of fluid dynamics and rock mechanics, In this paper, a numerical simulation method is proposed to simulate the erosion failure of riverbed rock, which is coupled with the rock mass mechanics model when the average pressure and pulsating pressure are affected by the water flow. Numerical simulation of the erosion process of riverbed bedrock is realized. (4) the mechanical model of riverbed rock mass erosion is established, and the two-dimensional model of jointed rock mass is established in the general discrete element program UDEC, and the fracture water pressure is loaded. The break-up failure model of jointed rock mass under the action of ejection flow is verified by the uniform pressure and pulsating pressure. Dynamic response processes such as failure of rock joints, fragmentation and movement of rock masses are obvious in the model. (5) the effect of dynamic load on erosion is studied. The difference of dynamic response of rock mechanics model is studied by changing the frequency and peak stress of the loaded sinusoidal stress wave.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV135;TV651.1

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