不同应力路径下大理岩破坏过程的声发射特性

对大理岩试样进行常规三轴和卸围压破坏过程的声发射参数测试,研究加荷和卸荷两种应力路径下大理岩破坏过程的声发射特性差异。结果表明,常规三轴试验中,声发射幅值随着围压的增加逐渐增大,岩样破坏前的声发射累计释放能量呈线性增加,最大振铃计数率和能量计数率不是出现在峰值,而是出现在峰后应力跌落阶段,峰值应力前的屈服阶段和残余强度前各存在一个平静期,振铃计数率的每个突增都与应力降相对应。卸围压试验中,岩样破坏后声发射幅值明显增大,卸荷开始后振铃计数率和能量计数率出现突增,声发射累计释放能量呈非线性迅速增加,根据声发射累计释放能量增速可以将岩样破坏过程分为3个阶段:弹性阶段、弹塑性阶段和塑性阶段,在大规模声发射出现前期会出现平静期,两者会交替发生。与常规三轴试验相比,卸荷声发射振铃计数率更大,累计释放能量更高,说明大理岩卸荷破坏更加剧烈。

ACOUSTIC EMISSION CHARACTERISTICS OF MARBLE DURING FAILURE PROCESS UNDER DIFFERENT STRESS PATHS

The acoustic emission parameter tests of marble are carried out under loading and unloading conditions.The results show that the acoustic emission(AE) characteristics change with stress paths.In triaxial loading test,the AE amplitude increases with the increase of confining pressure.The cumulative energy increases linearly before rock failure.The biggest ring count rate and energy count rate don t appear at the peak stress,but in the residual stage.There exists a quiet period of AE before the peak stress and residual stress.Each sudden increase of ring count rate corresponds to a stress drop.In triaxial unloading test,the AE amplitudes are larger before rock failure than those after rock failure.The ring count rate and energy count rate increase quickly at first.The cumulative energy increases nonlinearly during unloading process.Rock failure process can be divided into three stages according to the increase speed of cumulative energy:elastic stage,elastoplastic stage,plastic stage.There exists a quiet period of AE before the large-scale AE appears.Compared with the triaxial loading test,the biggest ring count rate and cumulative release energy are higher,which indicates rock failure of unloading test is more violent.