Abstract: Seepage control of dam foundation is a key issue that needs to be solved in dam construction with deep overburden. Finite element method is employed to analyze the seepage characteristics of geomembrane impervious earth-rock dam on deep overburden. The study focuses on the impact of the depth of suspended cut-off wall, the depth of overburden, and permeability on the seepage field of dam foundation. Results reveal that the seepage characteristics of dam foundation are significantly affected by these factors. Under varying depth of cut-off wall or overburden layer, the relation curves of seepage versus relative seepage control depth conincide in general, displaying a trend of slow linear decline before dramatic reduction. The depth of cut-off wall and overburden layer jointly affect the seepage control effect. When suspended cut-off wall is adopted, the relative anti-seepage depth should be in a good logarithmic linear correlation with permeability coefficient of overburden to ensure that the dam seepage control rate reaches 75%. This fitting relation can be used for preliminary design of cutoff wall depth for similar projects or effect evaluation of cutoff for existing projects.

Key words: geomembrane faced rockfill dam, deep overburden, seepage characteristics, relative impermeable depth, control rate of seepage flow