Abstract: The Kala Hydropower Project, located in a narrow and deeply-cut valley on the middle course of the Yalong River, is subjected to serious seepage and leakage problems due to complex geological conditions at the dam site. In order to reduce the quantity of seepage flow through and around the gravity dam and prevent the dam and its foundation from seepage failure, a seepage control system consisting of grouting curtain, drainage hole array and drainage tunnels is designed. For performance assessment and optimization design of the seepage control system, 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) is adopted. Numerical results at a typical overflow dam section and the whole dam site demonstrate that the primary design is a proper and considerable scheme for seepage control but further optimization can be performed in designing the layout. The results show that: ① the grouting curtain can effectively raise the groundwater level at the upstream of the grouting curtain, increase the bypass seepage path and reduce the uplift pressure in the dam foundation, and the drainage system can significantly reduce the pore water pressure in the dam body and the uplift pressure in the dam foundation; ② the drainage hole spacing has significant effects on the free surface locations with an appropriate spacing of 3.0~4.5 m.

Key words: Kala hydropower project, seepage control, SVA method, numerical simulation