循环加卸载下花岗岩强度变形及声发射特征

摘要

Aimed to study the characteristics of strength and deformation along with acoustic emission under cyclic loading,uniaxial and triaxial cyclic loading-unloading compression tests on granite were carried out using MTS815 system.Test results show that the "concave-upward" phenomenon of deviatoric stress-axial strain curves and the "migration" of hysteresis loops under the triaxial cyclic compression are not so obvious as those under the uniaxial compression.The peak strength and peak strain have a good linear relationship with confining pressure.During the uniaxial and triaxial compression tests,the elastic modulus and the Poisson's ratio of the first five cycles increase with the increase of cycle times,while the elastic modulus decreases at the last loading-unloading cycle.In the uniaxial cyclic test,the specimen demonstrates columnar splitting failure,but it shows obvious shear failure during the triaxial cyclic test.The AE ringing counts during the last loading-unloading cycle in the triaxial test are significantly less than those in the uniaxial case.Besides,a platform can be detected at each stage of the damage duration curve for the uniaxial cyclic loading,whereas it is not obvious in the triaxial test,implying that the damage of rock specimen experiences a show growth.%为了研究花岗岩在循环荷载作用下的强度、变形及声发射特征,采用MTS815岩石力学试验机开展了单轴和三轴循环加卸载试验.结果表明:三轴循环压缩下偏应力-轴向应变曲线的上凹现象和滞回环的迁移现象相比于单轴不太明显;峰值强度和峰值应变与围压间呈现良好的线性增长关系;单轴循环加卸载下,试样表现出柱状劈裂破坏,而在三轴循环加卸载下,试样则具有明显的剪切破坏特征;前5次的循环下加载、卸载段的弹性模量和泊松比都随着循环次数的增大而增大,而在最后一次加载段弹性模量有所降低;三轴循环下试样在最后一次加卸载破坏时产生的声发射振铃计数要明显少于单轴循环.此外,在单轴循环下,每一次加卸载阶段对应的损伤-时间曲线都会出现平台,而三轴下对应的损伤-时间曲线并未出现明显的平台,表明岩样损伤保持平缓增长.