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 parametersfandcof Jinping arch dam abutment faults material and weak rock mass have significant hydraulic pressure weakening effect. In the strength parameters, the friction coefficientfchanges a little while the cohesioncsignificantly 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 strengthτof the main faults f2、f5、f13、f14、f18 is at around 25%,and the average weakening rate of the anti-shear strengthτof 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.
