花岗岩应变岩爆声发射特征及微观断裂机制

ACOUSTIC EMISSION CHARACTERISTICS OF GRANITE UNDER STRAIN ROCKBURST TEST AND ITS MICRO-FRACTURE MECHANISM

对真三轴应力状态下的突然卸载应变岩爆试验监测到的声发射原始波形数据进行频谱分析和时频分析。根据三亚花岗岩岩爆试验前后样品SEM微观结构照片,岩爆过程的声发射频谱特性及声发射参数RA值(声发射撞击上升时间/幅度)的不同,分析其破坏过程的微观机制。在试件相对稳定阶段,产生以低幅、低能量释放为特征的波,对应微裂纹的滑移或局部的微裂纹开裂;在岩爆发生时声发射波除低频部分的幅值明显增大之外,高频幅值也有增大趋势,表明有高能量释放,试件内产生宏观破裂;岩爆前RA值增加,岩爆时降低。高RA值是张裂纹形成产生的波,低值是剪切裂纹形成的波。试验结果揭示岩爆过程中同时产生大量的高频低幅特征的波和低频高幅特征的波,分别对应形成穿晶或解理微裂纹,以张裂纹为主及沿晶或穿晶宏观裂纹,以剪切裂纹为主,显示高能量释放及低RA值特征。

The frequency-spectrum and time-frequency characteristics of acoustic emission original wave data are analyzed, which are obtained through monitoring strain rockburst test under true triaxial stress state with special characteristics of unloading one side of the specimen suddenly. The micromechanism of rock failure process is analyzed based on the microstructure SEM（scanning electronic microscope） images of Sanya granite samples before and post failure, frequency-spectrum and RA（rise time/amplitude） characteristics ofAE waveform obtained during rockburst. When the rock sample is relatively stable, AE waves with the feature of low-amplitude and low-energy are formed, and microcracks slip or split in local zone correspondingly. However, the amplitudes of AE waves increase not only in low-frequency range but also in high-frequency during rockburst, which implies that high energy is releasing and macrocracks in the rock specimen are generated. The RA values increase before rockburst and decrease during rockburst. High RA value is wave generated by tensile cracks and low RA value is wave generated by shear cracks propagation. The test results reveal that many relative high-frequencylow-amplitude waves and low-frequency-high-amplitude waves generated during rockburst are related to transgranulation/cleavage tensile microcracks and intergranular shear macrocracks respectively, which shows the characteristics of high energy releasing and low RA value.