水布垭面板堆石坝垫层料渗透与渗透变形特性试验研究

水布垭水电站混凝土面板堆石坝高达233 m，垫层料的良好性能对于大坝的变形和渗流控制极为重要。文中介绍了基于混凝土面板堆石坝工程建设经验以及水布垭水电站可行性研究阶段试验成果确定的垫层功能要求和垫层料具体设计要求，垫层料的渗透性和渗透变形特性在设计要求中占有重要的位置，详细介绍了施工设计阶段针对垫层料进一步开展的系列渗透变形试验。水平试验取得的渗透系数、临界比降、破坏比降均有大于垂直试验值的趋势，水平试验模型更接近垫层实际填筑情况及其中的水流流态，所以水平试验成果更反映垫层的工程特性；随着垫层料级配和密度的变化，其渗透系数变化范围较大，总体上满足10-4～10-2 cm/s渗透系数的要求。但是，粗级配和低密度试样的渗透系数超越设计要求的上限值；临界比降和破坏比降随着垫层料级配和密度的变化没有呈现明显的规律变化，试样内部结构欠稳定。研究成果进一步说明，垫层料级配和填筑密度控制非常重要，垫层的渗透稳定性有赖于过渡区提供有效的反滤保护作用。

Studies of permeability and seepage deformation characteristics of cushion material for Shuibuya Concrete Faced Rockfill Dam

The height of the concrete faced rockfill dam (CFRD) of Shuibuya hydropower Station is up to 233 m. The properties of the cushion material are very important for the dam deformation &; seepage control. Based on the CFRD construction experiences of the world and the test results at feasibility study of Shuibuya Projects, the function of the cushion layer and the design requirements for its materials are discussed. The permeability and seepage deformation characteristics are pivotal among the design requirements. A series of seepage deformation tests on cushion material performed further at construction design stage are expounded. Permeability, critical and failure hydraulic gradient from horizontal model tests are higher than those from corresponding vertical model tests. Horizontal models simulate better the situation of filling and flow pattern in the cushion layer of the real dam. So the results from horizontal models approach more closely to the properties of the cushion layer. With different gradation curves and density values, the permeability varies in a large range. It is mainly between 10-4-10-2cm/s as required, but the coarser materials with low density would exceed the upper permeability limit. The critical and failure gradient does not changes so regularly as gradation curve and density varies. The interior structure of the material would not be stable. The results emphasize further the importance to control the material gradation and filling density. The seepage stability of the cushion layer must be supported by the transition zone with efficient filtering and protection.