深部花岗岩50℃卸荷蠕变试验研究

Experimental study on unloading creep of deep granite at 50 ℃

为研究深部花岗岩在温度作用下的卸荷蠕变特性,采用岩石全自动三轴流变仪开展了花岗岩在温度50℃、围压10、20、30 MPa条件下的卸荷蠕变试验,分析了花岗岩高温卸荷蠕变特征、宏观破坏模式和微细观损伤破坏机理.试验结果表明:在温度效应条件下,花岗岩高压卸荷蠕变会产生较大变形;50℃卸荷蠕变条件下,花岗岩的蠕变性能随着围压的卸载而呈指数变化,初始卸荷围压越高,花岗岩越早出现蠕变变形;花岗岩高温卸荷蠕变破坏模式主要为共轭剪切破坏,蠕变作用促使岩石内部损伤裂隙扩展并形成裂隙面而失效破坏;岩石高温卸荷蠕变破坏强度约为常温三轴强度的1/3,其黏聚力和内摩擦角也比常规指标减少30%以上.

To study the unloading creep characteristics of deep granite at high temperature, the unloading creep tests of granite were carried out under the confining pressure of 10, 20, 30 MPa at 50 ℃ by using the rock automatic triaxial rheometer. The unloading creep characteristics, the macroscopic failure modes and the microscopic failure mechanism of granite at high temperature were studied. The experimental results show that the granite produces large creep deformation under high pressure unloading by the effect of the temperature. The creep performance of granite changes exponentially with the unloading at the temperature of 50 ℃. The higher the initial unloading confining pressure is, the earlier the creep deformation of granite appears. The main unloading creep failure mode of granite is shear failure at 50 ℃. The creep effect promotes the propagation of internal damage cracks and fracture surfaces are formed, thus leading to failure. The failure strength of unloading creep at high temperature is about 1/3 of that of the triaxial strength. Compared with the traditional indicators, the cohesion and the internal friction angle reduce more than 30%.