Based on the characteristics of geology and landform of the levees in the Dongting Lake region

a generalized model of vertical cutoff wall on multi-structure levee foundation has been established; then following the optimization concept and using the seepage FEM

a systematic study of the relationship between the vertical cutoff wall penetration in sand and gravel layer or the relative impermeable layer and the maximal seepage gradient inside levee is carried out. Then based on the FEM results

the comprehensive and objective estimation about the effect of anti-seepage of the two types is introduced. And a definition called critical optimization penetration is put forward for the first time. Finally

seepage FEM is applied to high pressure grouting cutoff wall project in Dadongkou Electric Drainage Project; the safe operation of real project shows that the analysis of this paper is right and practical.