不同应力路径下砂岩能耗变化规律试验研究

EXPERIMENTAL STUDY ON ENERGY EVOLUTION OF SANDSTONE UNDER DIFFERENT STRESS PATHS

为研究不同应力路径下岩石的能耗变化规律,采用MTS815岩石力学试验系统开展了砂岩的单轴压缩、常规三轴和卸荷三轴试验。结果表明:耗散能曲线变化是岩石内部损伤和破裂产生的表现,在弹塑性变形阶段,常规三轴耗散的能量占岩石吸收总能量的比例最大,卸荷三轴次之,单轴压缩最小;岩石的储能极限与围压具有明显的线性关系,单轴压缩试验中岩石的储能极限最低,卸荷三轴次之,常规三轴试验岩石的储能极限最高;岩石峰前和峰后的能量耗散速率与围压也具有良好的线性关系,峰后应力跌落阶段能量耗散速率明显较峰前能量耗散速率大数倍至数十倍,说明岩石峰前损伤速率较小,而峰后却快速损伤破裂,耗散能曲线的突然变陡表明岩石破坏发生。

In order to study the energy evolution characteristics of rock, conducting uniaxial compression test, conventional triaxial compression tests and unloading triaxial compression tests of sandstone were performed by an MTS815 rock mechanics test system. The results show that： the increase of the dissipated energy is the performance of the internal damage and crack growth; in the elastic-plastic stage, the percentage of dissipated energy in proportion to total energy under conventional triaxial compression test is larger than that of unloading triaxial compression test and uniaxial compression test; the maximum limit storage energy increase linearly with confining pressure; under conventional triaxial compression test, the rock has the highest energy storage limit, the unloading triaxial compression test takes the second place and uniaxial compression test is the lowest. The increasing rate of dissipated energy before and after peak strength also have a good linear relationship with confining pressure; the rate after peak strength is much bigger than that before peak strength; it shows that the damage rate before peak strength is small, while damage develop rapidly after peak strength, and the suddenly steep increase of dissipated energy indicate the occurrence of rock failure.