均质土坝漫顶溃决“陡坎”移动参数确定

“陡坎”冲蚀是均质土坝漫顶溃决时的主要破坏模式,“陡坎”移动的速度与坝料的物理力学指标具有内在联系,而目前国外给出各类“陡坎”移动模型很少考虑这些联系,且参数选取方法误差较大。基于水流能量耗散原理的“陡坎”移动速度模型,考虑坝料的黏粒含量、含水率、干密度等因素,参考国内外具有实测“陡坎”移动速度资料的水槽模型试验成果,拟合出“陡坎”移动参数的表达式,并结合水槽模型试验不同坝料的特点,给出了拟合“陡坎”移动参数的上下包线。参考美国农业部农业研究中心开展的7组均质土坝漫顶溃决试验的“陡坎”移动速度实测资料,验证了建议参数的合理性,并与国外典型的“陡坎”移动参数模型计算结果进行比较,给出了参数取值的参考方法;对“陡坎”移动参数中涉及的黏粒含量、含水率、干密度等指标进行参数敏感性分析,分析研究3个指标对“陡坎”移动规律的影响,为均质土坝漫顶溃决模型“陡坎”运移参数的选取和进一步研究“陡坎”抗冲蚀能力内在机理提供参考依据。     

上游水电站围堰漫顶溃决条件下施工中期度汛水位数值模拟

比邻梯级水电站同期建设条件下,若上游水电站围堰遭遇超标洪水发生漫顶溃决,将严重威胁下游水电站施工中期度汛的安全,因此,对度汛水位变化过程进行数值模拟具有重要意义。基于水动力学理论方法,建立了上游水电站围堰漫顶溃决条件下中期度汛水位变化过程模拟的数学模型,并将该模型应用于大渡河流域某相邻梯级水电工程实例中。通过不同计算方案的数值模拟分析,结果表明:该模型及方法是可行的、有效的;相比于基于天然洪水流量的计算方法,所提方法更加贴近工程实际,且度汛最高水位明显增大,因而更有利于工程安全。研究成果为上游水电站围堰挡水条件下的施工中期度汛方案决策及防洪应急预案的制定提供了重要的理论依据。     

基于Copula函数的大坝洪水漫顶风险率计算

洪水漫顶风险率分析计算对于大坝风险管理具有重要意义。本文基于Copula函数计算大坝洪水漫顶风险率，并分析不同Copula函数及峰量相关性对漫顶风险率的影响。清江流域隔河岩水库实例表明：最优的Gumbel-Hougaard Copula函数能较好地描述洪峰、洪量的上尾相关性，计算的洪水漫顶风险率为3.79×10-5，而Frank和Clayton Copula函数得到的风险率明显偏低。随着洪峰、洪量相关系数的增加，洪水漫顶风险率也增加。假设峰量相互独立的情况下洪水漫顶风险率被低估，而完全相关的情况下则被高估。基于Copula函数的两变量统计方法能够有效捕捉洪峰、洪量的实际相关关系，得到的风险率更加合理，为大坝洪水漫顶风险率分析提供科学依据。     

Hybrid numerical methods to solve shallow water equations for hurricane induced storm surge modeling

In this paper an efficient numerical method based on hybrid finite element and finite volume techniques to solve hurricane induced storm surge flow problem is presented. A segregated implicit projection method is used to solve the 2D shallow water equations on staggered unstructured meshes. The governing equations are written in non-conservation form. An intermediate velocity field is first obtained by solving the momentum equations with the matrix-free implicit cell-centered finite volume method. The nonlinear wave equation is solved by the node-based Galerkin finite element method. This staggered-mesh scheme is distinct from other conventional approaches in that the velocity components and auxiliary variables are stored at cell centers and vertices, respectively. The present model uses an implicit method, which is very efficient and can use a large time step without losing accuracy and stability.The hurricane induced wind stress and pressure, bottom friction, Coriolis effect, and tidal forcing conditions are implemented in this model. The levee overtopping option is implemented in the model as well. Hurricane Katrina (2005) storm surge has been simulated to demonstrate the robustness and applicability of the model.     

加筋无黏性土石坝漫顶溃坝试验研究

研制了封闭式循环供水土石坝溃坝模型试验装置,并应用该装置开展了室内模型试验,对加筋无黏性均质土坝的溃坝过程进行了系统研究,探讨了坝体加筋对溃坝流量过程线的影响规律。研究结果表明:在水泵出水口设置消能弯管和挡水隔板可保证模型上游供水的稳定性,在试验装置侧面设置连接上下游的U型测流弯管,把明渠流转化为满管管流,在U型弯管下侧平直段安装电磁式流量计量测溃口流量,可有效提高流量过程线的测量精度;加筋无黏性均质土坝的漫顶溃坝过程可分为坝体下游未加筋区域、加筋嵌固区和上游未加筋区域破坏3个阶段;随着加筋体埋深的增加,峰值流量呈现先增大、后减小,再增大的变化规律,在坝高的35%~50%范围内埋设加筋体,能够降低溃坝峰值流量;减小加筋体竖向间距能有效延滞溃坝峰现时间。     

Reducing Erosion of Earthen Levees Using Engineered Flood Wall Surface

Erosion was one of the major causes for the failure of New Orleans levee system during Hurricane Katrina. Protection of flood walls from erosion failure can be achieved in many different ways. This study consisted of experimental research to develop engineered flood wall surfaces that can reduce the erosion energy of the plunging water before the water hits the levee surface, so that the flood protection system becomes more resilient. Test results were compared to hydrodynamics simulation results by using FLOW3D. The results revealed that the erosion resistance of levees can be substantially reduced by providing protective structures at the surface of the flood walls. An effectively designed protective structure could reduce the erosion depth as much as 40% and extend the erosion time as much as 400%.     

土石坝漫顶溃决过程模拟

随着全球气候形势异常,局地极端强降雨频发,我国小型水库的安全度汛工作面临严峻形势,对小型水库开展必要的溃坝风险分析工作是非常必要的.以山东某小型水库为研究对象,分析计算了该水库在遭遇校核洪水和溃坝洪水两种情景下对下游高速铁路的影响,所得结果可以为相关管理单位应对溃坝风险提供决策支持.     

尾矿库漫顶溃坝数学模型研究与应用

基于水砂混合物非平衡连续方程和动量方程,考虑尾矿库溃坝过程中溃口及底床变化对溃坝下泄物中尾矿砂体积浓度的影响,建立了一个描述尾矿库漫顶溃坝溃口发展过程和溃口下泄物流量过程的数学模型。应用该数学模型对某尾矿库漫顶溃坝过程进行了模拟,结果表明,尾矿库溃坝过程中下泄物体积浓度变化很大,前期下泄物以水为主,尾矿砂含量较低且以悬移质运动为主;后期下泄物主要以尾矿砂为主,水的含量很低,尾矿砂以推移质运动为主,当下泄物底床剪应力增量小于尾矿砂起动的临界剪应力时,溃坝过程停止。     

Overtopping Probability Constrained Optimal Design of Composite Channels Using Swarm Intelligence Technique

In this paper swarm intelligence based methodology is proposed for optimal and reliable design of irrigation channels. The input parameters involved in channel design are prone to uncertainty and the solution of deterministic model may result in flooding risk and affect the stability of the channel. To provide reliability in the design, an overtopping probability constrained design is presented in this study. The deterministic equivalent of the probabilistic constraint is derived by following the principle of first order uncertainty analysis. In order to account for the uncertainty of design parameters in the objective function, a modified cost function is proposed. A methodology is propounded to solve it in a metaheuristic environment and solved it using elitist-mutated particle swarm optimization (EMPSO) method. The EMPSO based solutions are found to be quite successful and better than the classical optimization methods. Finally, it is concluded that the proposed methodology has a good potential for reliable design of composite channels for designer specified reliability values.     

LHS-MC与Copula函数在洪水漫坝率计算中的应用

综合考虑洪峰与洪量双变量,提出了基于LHS-MC与Copula函数及三点式变倍比放大法的洪水漫坝率计算方法,计算了HYT水电站加固前后的洪水漫坝率,同时分析了洪量选择和风浪作用对结果造成的影响。结果表明,HYT水电站加固后有效提高了大坝的抗洪能力,且在漫坝率的计算中洪量选择和风浪作用均应计入考虑。可见所提方法具有较强的适用性,能较全面的考虑洪水的影响因素,在分析各类大坝的洪水漫坝率时合理有效。