Abstract:The dam abutment rock samples of weak rocks and structural planes of Jinping I High Arch Dam were collected

the similar specimens were prepared

and the test conditions were determined through the analysis of characteristics of arch dam running environment.Then the triaxial compression tests and the water-rock coupling triaxial compression tests were conducted in the test system of rock mechanics MTS. Results indicated that the strength parameters f and c of Jinping arch dam abutment faults material and weak rock mass have significant hydraulic pressure weakening effect. In the strength parameters

the friction coefficient f changes a little while the cohesion c significantly decreases when the water pressure increases. Considering the combined effect of both strength parameters

under engineering condition of 10MPa normal stress and 3MPa water pressure

the average weakening rate of the anti-shear strength τ of the main faults f2、f5、f13、f14、f18 is at around 25%

and the average weakening rate of the anti-shear strength τ of the lamprophyre dike X and other weak rock mass is about 40%. This quantitative test results of weakening effect can provide an important scientific basis for the methods of geo-mechanical model test and numerical calculation to analysis and evaluate the stability of high arch dam.