过渡层与垫层的联合抗渗作用以及过渡层参与承担渗透坡降的作用机理是垫层料抗渗设计中一个值得关注的问题。本文采用室内常规渗透仪分别对有无过渡料保护条件下垫层料的渗透特性进行了试验研究。结果表明：在渗透仪底部铺一层直径为20~40mm的砂砾排水层、并在试样中加1%的水搅拌均匀是减少小于5mm颗粒对渗透仪透水板的淤堵效应，防止砂砾料发生颗粒离析的有效措施。随渗透坡降增大，垫层料渗透系数逐渐增大，过渡料渗透系数逐渐变小，垫层料中的细颗粒发生迁移进入过渡料，在过渡料与垫层料接触带上形成厚度约为1cm的自滤反滤层。在过渡料保护下，垫层区料的破坏坡降得到较大提高，过渡区料能够对垫层区料起到反滤保护及排水作用。%The combination seepage functions between transition material and cushion material and that the transition material involved in undertaken seepage gradient are wel-known problems in the seepage resistance design of cushion material. In this paper,the seepage deformation of sandy gravel cushion material which under or without the protection of transition material were studied by lab permeameter. It shows that paving a drainage layer with diameter of 20~40mm’s sandy graves in the bottom of the meter and uniformly mixing 1% waters in the sample are effective measures to decrease the blinding of porous plate by the particles which were smal er than 5mm and prevent the particle segregation of sandy gravel samples. With the increase of seepage gradient, the coefficient of permeability of cushion material increased while that of transition material decreased,the fine aggregates of cushion material migration into transition material,which formed about a 1cm filter at the contact zone. Transition material can taking effect as filter protection and drainage to cushion material, with its protection,the failure seepage gradient of cushion material gained a great improvement.
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