考虑温度效应的片麻状花岗岩三轴蠕变试验研究

Triaxial creep test of gneissic granite considering thermal effect

随着地下洞室开挖深度的增加,温度已成为影响洞室长期稳定的重要因素。为有效反映温度对深埋地下洞室围岩长期稳定的影响,依托某水电站引水隧洞工程,开展了不同温度和不同加载应力路径条件下片麻状花岗岩的三轴蠕变试验,系统分析了温度、围压、轴压对片麻状花岗岩蠕变变形特征、蠕变强度和蠕变破坏模式的影响。通过蠕变试验发现:片麻状花岗岩的蠕变性能随着加载应力的增大和温度的升高而呈指数变化;片麻状花岗岩存在蠕变应力阈值,且温度越高,蠕变应力阈值越低,蠕变破坏时间越短;片麻状花岗岩稳态蠕变速率随温度的升高而增大,符合指数关系,其蠕变长期强度和蠕变破坏强度均随温度的升高而降低;在温度效应条件下,片麻状花岗岩蠕变破坏模式主要为沿斜截面的剪切破坏。试验研究成果为水电站引水隧洞围岩长期稳定性分析与设计、施工提供了重要的试验依据。

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.