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采用岩石声波、声发射一体化监测装置,系统地研究三轴多级循环荷载作用下盐岩超声波波速与声发射变化特征。结果表明:(1)岩石的超声波波速和声发射活动与应力状态呈现出良好的一致性。加载阶段,超声波波速上升,声发射活跃,卸载阶段,超声波波速下降,声发射平静,应力级数越高,这一特征越显著。(2)盐岩的声波、声发射特征与试验围压应力密切相关。围压水平越低,应力循环试验中岩石波速变化率越大,声发射事件数量越多;围压水平越高,岩石超声波波速变化率越小,声发射事件数量越少。五级应力荷载试验中,围压条件为5,10,15,20 MPa时盐岩的声发射事件数量分别为1 026,703,361和206个,显示了“围压致密效应”。(3)分别应用卸载模量、裂隙密度和Felicity比表征盐岩的损伤演化。结论认为:盐岩的裂隙密度和Felicity比变化与岩体承载破坏特征较为一致,可以较好地反映盐岩的损伤破裂过程,而利用卸载模量表征盐岩损伤误差较大,这是由于盐岩特殊的黏塑性变形特征造成的。
A rock sound wave and acoustic emission integrated monitoring device was used to systematically study the characteristics of salt rock ultrasonic wave velocity and acoustic emission changes under triaxial multi-stage cyclic loading. The results show that: (1) The ultrasonic wave velocity and acoustic emission activity of rock show a good agreement with the stress state. During the loading stage, the ultrasonic wave speed rises, the acoustic emission is active, the unloading phase, the ultrasonic wave velocity decreases, the acoustic emission is calm, and the higher the stress level, the more significant this feature is. (2) The acoustic and acoustic emission characteristics of salt rock are closely related to the test confining stress. The lower the confining pressure level, the greater the rate of change of rock wave velocity in the stress cycle test, the greater the number of acoustic emission events; the higher the confining pressure level, the smaller the rate of change of the ultrasonic wave velocity of the rock and the smaller the number of acoustic emission events. In the five-stage stress load test, the number of acoustic emission events of salt rock at the confining pressure conditions of 5, 10, 15 and 20 MPa was 1,026, 703, 361 and 206, respectively, showing the “dense pressure effect of confining pressure”. (3) The unloading modulus, crack density, and Felicity ratio were used to characterize the damage evolution of salt rock. The conclusion is that the change of fracture density and Felicity ratio of rock salt is consistent with the characteristics of rock mass bearing failure, which can better reflect the damage process of salt rock, while the use of unloading modulus to characterize the salt rock damage error is larger due to salt Rock caused by the special viscoplastic deformation characteristics.