混凝土面板砂砾石坝漫顶溃坝数值模拟

Numerical simulation for concrete-face sand-gravel dam breaching due to overtopping

通过溃坝案例的现场调查和水槽模型试验,建立了面板砂砾石坝漫顶溃坝数学模型,以模拟水流特性、砂砾石料以及混凝土面板三者之间的相互作用。该模型主要由3部分组成:(1)考虑漩涡水流和砂砾石料之间的冲蚀特性,引入RNG k-ε湍流模型模拟漩涡水流的反向侵蚀;(2)通过泥沙输移公式和流体体积法(VOF法)追踪砂粒与水流侵蚀交界面,并考虑了砂砾石料的孔隙特性;(3)基于弯矩平衡法判定混凝土面板在自重和水荷载作用下的破坏过程。通过水槽模型试验对数学模型进行验证,结果表明,建立的数学模型能够准确地模拟溃决过程中漩涡水流对大坝的反向侵蚀和面板溃口的详细演化过程;该模型计算的溃口流量、堆石体溃口的发展、溃坝历时以及面板的折断长度,与实测数据的相对误差均小于15%,验证了模型的合理性。与参数化模型相比,本研究提出的溃坝模拟数学模型具有更详细的结果。

Based on the field investigation of dam break cases and flume model test,the numerical model of overtopping break of concrete-face sand-gravel dam(CFSGD)is established to simulate the interaction among water flow characteristics,sand-gravel materials,and concrete face slab.The model is mainly composed of three parts:(1)Considering the erosion characteristics between the vortex water flow and sand-gravel materials,the RNG k-εturbulence model is introduced to simulate the reverse erosion of the vortex water flow.(2)Through the sediment transport formula and fluid volume method(VOF)traces the interface between sand and water erosion,and considers the pore characteristics of sand-gravel materials.(3)Based on the moment equilibrium method,the failure process of the concrete face slab under its self-weight and water loads is calculated.The numerical model is verified by the flume model test.The results show that the numerical model established in this paper can accurately simulate the reverse erosion of the vortex water flow on the dam during the failure process and the detailed evolution process of the face slab breach.The relative error between the measured data and the calculated peak breach flow,the development of the breach of the rockfill body,the duration of the break and the length of the face slabs are all less than 15%,which verifies the rationality of the numerical model.Compared with the parametric model,the numerical model of dam breach proposed in this paper provides more detailed results.