Abstract: The engineering properties of high arch dam’s foundation rock change inevitably after excavation unloading, consolidation grouting and dam loading. The comprehensive deformation modulus of foundation rock mass is an important index for safety assessment and feedback analysis, but it cannot be obtained by field test. To solve this problem, we conducted researches on the geological condition, deformation test, borehole elastic modulus, and the relation between deformation modulus E₀ and longitudinal wave velocity V_p with Xiluodu hydropower station as an example. On this basis, we put forward a method of determining the comprehensive deformation modulus of foundation rock mass after the completion of high arch dam construction. The comprehensive deformation modulus of Xiluodu high arch dam foundation after construction completed is between 11-14 MPa. This parameter was used for 3-D numerical simulation, and the simulated deformation was in consistency with monitored deformation, which verified this method is appropriate.

Key words: high arch dam, dam foundation, comprehensive deformation modulus, determination of deformation modulus, Xiluodu hydropower station