岩桥直剪试验声发射频谱特征及主破裂前兆分析

Analysis of acoustic emission frequency spectrum characteristics and main fracture precursor of rock bridge in direct shear test

岩桥破坏的声发射研究一般只针对计数、能量等参数来分析。为探究岩桥直剪试验的声发射频谱特征,对岩桥进行声发射测试,利用时频分析方法对声发射波形信息进行研究,分析了其频谱特征。结果表明,直剪试验中幅值比计数率变化明显,且发生激烈响应的时间较早;主频基本呈高低频带状分布;主频带向中频分散和低频高幅值的声发射特征可作为试验主破裂的前兆信息,且前者出现较早;与单轴压缩试验相比,幅值在主破裂阶段区别明显,且此时出现中频值;声发射幅值由颗粒所受应力决定,频率与颗粒力链的最终位移有关;岩桥宽度增加,主频带整体升高;法向应力增加,平均主频值减小。研究可为节理边坡的稳定性分析提供参考依据。

The acoustic emission(AE) research of rock bridge failure is usually only based on the analysis of related parameters such as counting, energy and so on. In order to study the AE frequency spectrum characteristics of rock bridge in direct shear test, the characteristics of AE frequency spectrum are analyzed using time frequency analysis method. The results show that the amplitude is more obvious and the time of intense response is earlier compared with the counts rate in direct shear test. The AE dominant frequency is basically in the high and low frequency bands. The characteristics of the dominant frequency dispersing to intermediate and the low frequency having high amplitude can be used as precursor information of main fracture, and the former appears earlier.Compared with the result from uniaxial compression test, the amplitude in the main fracture stage is obviously different with intermediate frequency occurs at this time. The amplitude of AE is determined by the stress of particles, and the frequency is related to the final displacement of the particle force chain. With the increase of rock bridge width, the dominant frequency band increases, while the normal stress increases, the average frequency decreases. This study can provide reference for the stability analysis of joint slope.