应变型岩爆过程的声发射特征研究

采用真三轴岩爆试验系统开展岩石力学试验,在室内再现了花岗岩的应变型岩爆破坏、板裂破坏、真三轴剪切破坏三种破坏过程。研究表明,与板裂破坏、真三轴剪切破坏不同,在整体破坏前夕,岩爆破坏存在明显的声发射撞击数相对"平静期";三种破坏的声发射撞击数分形维数Dt都存在整体破坏前夕持续下降到极小值点而破坏瞬间突增的现象,但岩爆破坏在整体破坏前夕的Dt持续降低速率和整体破坏瞬间Dt增幅上都比板裂破坏的大;三种破坏过程的声发射信号的主频值呈"低频-高频-低频"的总体演化趋势,频谱形状经历"单峰-多峰-单峰"的交替变化过程,但在岩样破坏的塑性阶段,三种破坏在主频分布及信号幅值上有明显差异。

Experimental study of acoustic emission characteristics in strainburst process

Rock mechanics experiments were carried out using true triaxial rock burst experimental system.Three failure processes including strainburst,splitting and true triaxial shear failure of granite have been reproduced indoors.Experimental results show that on the eve of the whole failure, there is a distinct relative "quiet period"of acoustic emission hits for strainburst failure,which is different from the splitting failure and the true triaxial shear failure.For three kinds of failure,the fractal dimension D,of acoustic emission hits presents same phenomenon that it continually drops to the minimum point before whole failure and increases suddenly when failure occurs.However,for strainburst,the continuous reduction rate of Dt on the eve of whole failure and the increase of Dt in the instant of whole failure are larger than that of splitting.The main frequency values of the acoustic emission signals in the three kinds of destructive processes show a general evolutionary trend of low frequency-high frequency-low frequency.The spectrum shape experiences the alternating process of "single peak-multi peak-single peak".But in the plastic stage of rock sample failure,the main frequency distribution and signal amplitude of the three kinds of failure are obviously different.