土石坝溃决过程与溃坝洪水演进数值模拟研究

The research about the earth and rockfill dam's breaking process and its downstream advance of freshet is very important to handle the sudden dam-breaking flood disaster and enhance the safety of agricultural water conservancy projects in China. The rich research fruits acquired in the dam-breaking experimental investigation field provide the theory base and rich verifying data .to its numerical simulation. In the process of earth and rockfill dam breaking, water flow pattern is very complex in the breach area, involves strong steady rapidly varied flow and sand sediment transporting, also accompanied by the partial dam body's sudden form changes in the fore-and-aft and transverse direction. In the .present time, the computation model of dam-breaking is one dimensional, its main component elements adopt computation formulas, and its computing precision is limited. In addition, the numerical model based on sediment transport theory can not reveal the multiple dam-breaking related phenomenons completely. In this .research project, by data analysis and theory study, it plans to deepen the understanding of the earth and rockfill dam breaking mechanism, to extract the mathematical expression formulas including the breach development in the fore-and-aft and transverse direction, to establish the dam body breaking mathematical model which integrates the subject theories such as hydraulics, soil .mechanics and sediment dynamics etc. It plans to build conservativeness numerical discretization format and develop its matchable treatment technology of moving boundary. Its final goal is to develop high precision numerical model including the process of dam breaking and advance of freshet, which can be applied to the .dam-breaking flood disaster predicting and provide powerful support to flood disaster evaluation in the flood storage and detention basin.

研究土石坝的溃决过程及其坝下游洪水演进，对于我国处置溃坝突发性洪水灾害，提升我国农业水利安全，具有十分重大的意义。溃坝试验研究取得了丰硕的研究成果，为数值模拟奠定了理论基础并提供了丰富的验证资料。土石坝的溃决过程中，溃口区域水流流态复杂，涉及到强非恒定急变流输沙，且伴随着坝体局部的纵向突变与横向突变，溃坝计算模型由于其一维性且其主体组成部分为计算公式，计算精度有限，而基于泥沙输运理论的数值模型尚不能全面描述这些现象。本项目拟通过资料分析与理论研究，进一步加深对土石坝溃决机理的认识，提炼出了基于溃决机理的溃口纵向与横向发展的数学表达式，并综合水力学、土力学以及泥沙动力学等学科知识建立坝体溃决的数学模型，构造具有TVD性质的守恒性数值离散格式，并研制与之相匹配的动边界处理技术，开发精度更高的坝体溃决过程-溃坝洪水演进相结合的数值模型用于溃坝洪水的预测，为蓄滞洪区洪灾评估提供更为有力的手段。

水库大坝是江河防洪工程体系的重要组成部分，也是开发和利用水资源、发展国民经济的重要手段，建国60多年以来，我国修建了大量的堤坝工程，这些堤坝工程在维护社会稳定和国民经济发展方面发挥了巨大作用。然而，随着运行期的增长，相当一部分工程的使用年限已接近或超过了其设计年限，堤坝老化问题日趋严重，存在较为严重的安全隐患。研究土石坝的溃决过程及其坝下游洪水演进，对于我国处置溃坝突发性洪水灾害，发布洪水预警，编制应急预案，提升我国应对突发安全事件能力等，具有十分重大的意义。. 本项目通过分析现有的土石坝溃坝模型试验资料，对目前的溃口理论与模型进行深入的研究，基于溃决机理并综合水力学、土力学以及泥沙动力学等学科知识选取了溃口冲蚀与展宽的数学表达式；在已有的研究基础上，研制了具有间断波捕捉能力的数值离散格式；研制了与数值离散格式相匹配的基于单元属性与界面属性的动边界处理技术，建立了基于有限体积法与TVD-MacCormack格式的坝体溃决-溃下洪水演进相结合的数值模型。模型采用非规则局部不连续网格划分计算区域，采用非结构网格管理模式组织计算网格。. 采用物理模型试验资料对数值模型进行了验证，并在实际工程上对数学模型进行了测试，研究结果表明：数值模型可合理地模拟坝体的溃决过程与坝下洪水演进过程；在溃口附近等急缓流过渡区表现出对间断波良好的捕捉能力，具备良好的稳定性；动边界处理技术对干湿剧烈变化区域具有较强的模拟能力；模型具备良好的守恒性。. 本项目建立的坝体溃决-溃下洪水演进相耦合的数值模型可为预测溃坝洪水灾害预测提供有力的技术支持。