高面板堆石坝面板发生挤压或张拉等破损，从而使面板出现局部集中渗漏点或条带是大概率事件，垫层防渗是防渗体系的第二道防线。研究了面板局部破损后垫层与过渡层中的水力条件。指出垫层必须是内部稳定的，过渡层必须对垫层构成反滤保护。过渡层一般也应满足内部稳定性条件。砂砾石的内部稳定性可以根据颗粒级配曲线判别。过渡层满足内部稳定性条件时，第二道防渗体系是渗透稳定的。若过渡层不能满足内部稳定性要求，非饱和情况下，过渡层也有可能发生管涌。非饱和渗流的管涌临界渗流速度，可通过流量可控的非饱和向下渗流试验测量。过渡层非内部稳定时，其中的渗流速度应小于非饱和临界渗流速度。

The real gradation of rockfill should be scaling on laboratory texts because of the limited size of apparatuses. The scaling will change the grading characteristics of rockfill，causing the scale effect and also exerts influences on texts. The scale effect of rockfill is influenced by many factors. The existing test results conducted by different researchers show different and even rever se trends. Based on existing researches， the influencing

factors including scale method， degree of compaction control standard， particle breakage， rock strength were summarized. The causes of such influences and the mesoscopic mechanism of rockfill scale effects were analyzed. Representative achievements and research progress were introduced. Relevant problems of scale effect were discussed. Th ese provide solid technical reserves for the design and build of high rockfill dam.