【摘要】 利用MTS岩石力学试验系统和PAC声发射信号采集系统,研究了砂岩在单轴压缩条件下应力-应变全过程的声发射特征以及加载速率对其的影响。获得了岩石轴向应力与轴向应变、横向应变、体应变之间的关系曲线,以及全应力-纵向应变过程曲线中4个阶段的声发射特征;在初始压密和弹性阶段,声发射撞击数少、能量低、振幅小、无事件数产生;在应变硬化阶段,撞击数骤增、能量高、振幅大、有大量事件数产生;在应变软化阶段撞击数骤减、能量低、振幅小、有事件产生。由于岩石每个变形阶段具有不同的声发射特征,因此,可用声发射来表征岩石的微观损伤演化和预测现场工程岩体的宏观断裂失稳过程。另外,随着加载速率的提高,岩石裂纹扩展速率会加快,损伤加大,从而产生更多的声发射;但峰值处释放能量的最大值呈递减趋势,产生强烈声发射的应变值变小。更多还原

【Abstract】 All characteristics of acoustic emission in the procedure of rock stress-strain and effect of loading rates were studied experimentally under uniaxial compression by using PAC acoustic emission acquisition system and MTS equipment.The relationship of axial stress with axial strain,transverse strain and volume strain of rock,as well as the characteristics of acoustic emission at four stages of the stress-strain curve were obtained.In initial consolidation and elastic phase,it is found out that hits seldom happens,energy keeps low,amplitude is small and no event is produced.In strain hardening phase,hits instantly increases,energy go up,amplitude enhanced and events happen.In strain softening phase hits decrease,energy became low,amplitude went back small and events happen.Due to the differences among acoustic emission characteristics in individual rock-transforming phases,acoustic emission method can be used to study micro-damage evolvement and predict macro-destabilization of engineering rock mass on spot.The failure damage evolution rule of sandstone under the different loading rates is studied based on the acoustic emission characteristics.The increase of loading rate can promote the rate of crack extension and damage,so there are more AE counts.But,intense AE events being,the energy release at the peak place and strain value decrease.更多还原