Abstract: With the increase of excavation depth of underground cavern, temperature has become the important factor influencing the long-term stability of the cavern. In order to reflect the influence of the temperature on the long-term stability of surrounding rock, the triaxial creep tests with different stress paths and temperature conditions were conducted relying on a hydropower station headrace tunnel engineering, and the influences of the temperature, confining pressure and axial pressure on the creep deformation characteristics, the creep strength and the creep failure mode of gneissic granite were analyzed systematically. The test results indicate that the creep properties of gneissic granite are exponential with the increase of loading stress and temperature. Gneissic granite possesses creep stress threshold, and with the increase of the temperature, the threshold lowers, the time of creep failure becomes shorter. The steady-state creep rate of gneissic granite increases exponentially along with the rise of temperature. The long-term creep strength and creep rupture strength decrease with the increase of temperature. Creep failure modes of gneissic granite are mainly shear failure along the inclined section. The results provide important experimental basis for the long-term stability analysis and design and the construction of hydropower station headrace tunnel.

Key words: hydropower station headrace tunnel, gneissic granite, triaxial creep test with thermal effect, creep deformation characteristics, creep long-term strength