Abstract: The foundation stratum of a concrete hyperbolic arch dam consists of near horizontal layered rockmass having relative soft layers in the upper abutment. There are obvious differences among rockmass behavior at different elevations. In this research, rockmass quality classification is carried out for the main bearing stratum at dam site, and then direct shear tests and deformation tests are conducted for thin limestone and calcareous mudstone interlayer nuddy dolomite. Test results are in agreement with the results of rockmass quality classification. Some engineering recommendations are also given in the light of dam foundation’s rockmass mechanical characteristics.

Key words: rockmass quality, mechanical parameters, test, engineering recommendation