Abstract: The criterion for available foundation rock mass of super-high arch dams over 200 meters is proposed through analyzing the factors of selecting available rock mass by engineering analogy method. The utilization of excavated foundation rock mass of seven super-high arch dams in China is investigated. Compression failure and shearfailure of super-high arch dams and dam foundations under loading pose requirements on the quality of dam foundation: sufficient bearing capacity, deformation resistance, shear resistance, and anti-sliding stability. In China, classification of rock mass quality is the general evaluation indicator for the selection of foundation rock mass of super-high arch dams. Different qualities of rock mass are required at corresponding positions: class-Ⅱ rock mass is regarded superb for the foundation rock mass of super-high arch dam; class-Ⅲ₁ could be used for the middle part of foundation; and class-Ⅲ₂ for the upper part. The deformation modulus and cohesive strength of rock mass in practical engineering are larger than the values suggested in specification. In conclusion, the selection of available rock mass for foundation surface of super-high arch dam is a process involving the demonstration of multiple factors on the premise of dam stability with mechanical properties and rock mass quality classification as general evaluation indicators.

Key words: super-high arch dam, excavated foundation surface, classification of rock mass quality, engineering analogy method, bearing capacity, deformation modulus, shear strength