Abstract: Rock mass surrounding the excavation also under the complex radial unloading and ring direction loading stress path due to the excavation, for which results in difference from that of rock mass strength，deformation property and failure mechanism. Aiming to the high in-situ stress characteristics of Jinping II hydropower station, four different stress paths are chosen as test schemes corresponding as the uniaxial compressive test, triaxial compressive test, unloading triaxial test and unloading confining – loading axial pressure full test under high stress conditions are carried out on the marble specimens from the drainage tunnel. The complete stress-strain curve，deformation properties，failure characteristics and limited energy storage are obtained under respective stress path. Some instructive conclusions are drawn from tests as follows: (1) The failure axial strain is generally small. Jinping marble is hard and brittle which more apparent under unloading conditions. (2) The axial strain, circumferential strain and volumetric strain value unloading confining – loading axial pressure full tests are generally higher in the unloading tests, peak strength conversely. (3) The deformation modulus is large and the peak strength is lower with larger unloading rate, the deformation modulus is lower and the peak strength is large with larger loading rate, the deformation modulus is lower and the peak strength is large with larger initial confining pressure. (4) The principally failure model is tension without confining pressure; shear failure and locally tensile failure with lower confining pressure; while shear failure shape is X or Y with higher confining pressure. (5) The rock specimens have the limited value of energy storage, which can be effected by various factors. Limited energy storage is large with high confining pressure and is lower with higher unloading stress rate. The results can offer valuable references in explaining the mechanism of rockbutst and solving underground rock engineering problems.

Key words: Jinping II hydropower station marble, unloading confining-loading axial pressure full test, limited energy storage