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开展大理岩岩样常规三轴加荷破坏试验研究,分析大理岩变形破坏过程各阶段声发射及其频率、b值变化特征,探索不同围压下岩石破坏前兆信息。结合极点对称模态分解方法(ESMD方法)对声发射数据进行去噪处理后的试验结果表明:三轴压缩破坏岩样声发射水平在压密阶段和弹性阶段较小,塑性阶段逐渐活跃,扩容应力后声发射水平显著提高,在峰前塑性阶段存在声发射平静期。岩样变形破坏过程中的声发射频率与b值整体表现为上下波动态势,加载初期声发射频率与b值波动较大,并保持在较高水平,塑性变形阶段声发射频率与b值变化幅度减小。与声发射平静期相对应,塑性阶段存在声发射频率与b值变化相对稳定阶段。低围压下岩石破坏前声发射频率与b值均出现骤降特征,岩石发生脆性断裂,高围压下岩石破坏前声发射频率与b值变化相对平稳,岩石发生渐进式破坏。
The triaxial tests of marble samples are carried out. The characteristics of acoustic emission, frequency and b value at different stages of marble deformation and failure are analyzed, and the precursory information of rock failure under different confining pressures is explored. Combined with the pole-symmetric modal decomposition (ESMD) method, the acoustic emission data are denoised. The experimental results show that the acoustic emission levels of triaxial compression damaged rock samples are smaller during the compaction phase and the elastic phase, while the plastic phase is gradually active. After the stress, the level of acoustic emission increased significantly, and the acoustic emission calm period exists in the plastic phase before the peak. Acoustic emission frequency and b value in the process of deformation and failure of rock samples show the tendency of fluctuating up and down. At the initial stage of loading, the acoustic emission frequency and b value fluctuate greatly and remain at a relatively high level. The variation of acoustic emission frequency and b value during plastic deformation stage Decrease Corresponding to the quiet period of acoustic emission, plastic phase has the stage of relatively stable change of acoustic emission frequency and b value. Before rock failure under low confining pressure, the acoustic emission frequency and b value all showed plunging characteristics. The rock fragile fractured. Before rock failure under high confining pressure, the variation of acoustic emission frequency and b value was relatively stable, and the rock was gradually destroyed.