炭质泥页岩剪切破坏声发射特性及其分形特征

Acoustic Emission of Carbonaceous Shale and Its Fractal Characteristics under Shear Failure

为了探究炭质泥页岩损伤细观机制和破坏前兆特征,通过剪切破坏声发射试验,结合分形理论,采用G-P(Grassberger-Procaccia)算法对振铃计数、能量、振幅进行相空间重构和关联维数计算,分析关联维数在炭质泥页岩破坏全过程的演化规律。结果表明:声发射活动在岩石不同变形阶段活跃程度不同,且在破坏前存在平静期;振铃计数、能量、振幅都具有分形特征,三者的关联维数在破坏全过程呈现出“升维—动态波动—降维”的演化规律;关联维数的降维现象出现在岩样破坏前,可作为炭质泥页岩失稳破坏的前兆特征;综合对比发现,与振幅和振铃计数相比,能量关联维数的降维现象更显著,持续时间更长,更适合作为炭质泥页岩失稳破坏的前兆特征。

In order to explore the mesoscopic mechanism of rock damage and the characteristics of precursor to destruction,the shear failure acoustic emission test was carried out on carbonaceous shale,the phase-space reconstruction and correlation dimension calculation of the three acoustic emission parameters were carried out by Grassberger-Procaccia(G-P)algorithm,and the evolution law of correlation dimension in the whole process of carbonaceous shale destruction was analyzed by using fractal theory.The results show that the acoustic emission activity is active in different stages of rock deformation,and there is a calm period.The acoustic emission ringing count,energy,and amplitude sequences all have fractal characteristics,and the correlation dimensions of the three show the change law of“ascending dimension-dynamic fluctuation-dimensionality reduction”in the whole process of destruction.The dimensionality reduction phenomenon occurs before the destruction of the rock and ends after the destruction of the rock sample,so it can be used as the precursor information of the rock instability failure as the calm period,and the dimensionality reduction phenomenon of the associated dimension of the ringing count and energy is more significant and lasts longer,which is more suitable as the precursor information of the rock instability failure than the amplitude.