Located at a narrow and deeply-cut valley in the middle reach of Yalong River in Southwestern China, the Kala Hydropower Station is subjected to serious seepage and leakage problems due to complex geological conditions at the dam site. A numerical method combining a substructure technique, a variational inequality formulation of Signorini’s type and an adaptive penalized Heaviside function (short for SVA method) was adopted for the simulation and assessment of seepage control effects at the dam site in Kala Hydropower Project. Numerical modeling of a typical overflow dam section and the whole dam site demonstrated that the primary design was a proper scheme for seepage control, and furthermore, optimization of the seepage control system can be performed in designing the layout.

Seepage problem is of great importance to the stability of the soil dams in deep overburden foundation which is composed of coarse-grained soils. With a discussion on the relationship between particle size distribution and seepage law of the coarse-grained soils, Darcy's law was applied to simulate the seepage flow process of the deep overburden foundation of the Wudongde project. The variational inequality approach of the Signorini's type was used to solve the seepage field of the cofferdam site to eliminate the singularity at the seepage points. The result illustrates that the seepage control system composed of a concreted cutoff wall and geo-membrane sloping wall exhibits perfect performance under normal operation conditions. The differences of the seepage field characteristics under different hydraulic conductivities combinations of overburden layers were discussed. Finally, stabilities under different operation situations were evaluated with linear and nonlinear analysis with a consideration of the effects of seepage process.