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针对孟底沟水电站坝区花岗岩开展了不同加卸载应力条件下的三轴蠕变试验,系统分析了不同加卸载过程中坝区花岗岩的变形特征、蠕变速率和破坏强度的变化规律,揭示了蠕变破坏模式。结果表明,孟底沟花岗岩存在蠕变应力门槛值,蠕变后期存在完整的减速、等速和加速蠕变阶段,岩石产生大量塑性变形,体积由压缩转为扩容;轴压恒定相比偏应力恒定卸围压蠕变更具时效特征,卸围压条件下出现劈裂和剪切共存的破坏模式;岩石破坏强度低于常规峰值强度,卸围压相比加轴压方式岩石强度下降幅度更大,粘聚力的降低是造成强度折减的主要因素。
According to the triaxial creep tests under different loading and unloading stress conditions for the granite in the dam area of Mengdi Gorge Hydropower Station, the deformation characteristics, creep rate and breaking strength of granite in different dam areas during loading and unloading are systematically analyzed. Creep destruction mode. The results show that there are creep stress thresholds in the Mengdiogou granite, complete deceleration, constant velocity and accelerated creep in the later stage of creep. The rocks produce a large amount of plastic deformation and the volume changes from compression to expansion. The axial compression constant is higher than the deviatoric stress The creeping of constant unloading confining pressure is more time-dependent, and the failure mode of splitting and shear coexistence occurs under unconfining confining pressure. The failure strength of rock is lower than that of conventional peak strength. The decrease of rock strength of unloading confining pressure compared with axial compression is more Large, cohesion reduction is the main factor resulting in strength reduction.