Abstract: The columnar basalt rock develops in the dam site area of Baihetan hydropower station. Its deformation modulus is relatively low owing to its poor integrity. Especially, it shows the characteristics of anisotropy and easy relaxation after excavation. It is the first time that the columnar basalt rock is chosen as the base of super high arch dams at the site of Baihetan Hydropower Station. The structural form of expanded foundation was put forward for the design of the super high arch dam to adapt to the characteristics of the columnar basalt at the base. By applying the three-dimensional finite element method, the thrust force expanding mechanism and the effect of expanded foundation were studied, and the effect of the relaxation of the columnar basalt on the arch dam was also studied. The capability of the expanded foundation of the arch dam to adapt to the foundation characteristics of the columnar basalt rock layers was demonstrated by computation results.

Key words: Baihetan hydropower station, columnar basalt, super high arch dam, expanded foundation, numerical modeling