不同应变率下岩石冲击破坏的声发射特性研究

Acoustic Emission Characteristics Analysis of Rock under Impact Loading of Different Strain Rate

为了研究在动载荷下岩石破裂的声发射特性,采用霍普金森(SHPB)实验系统对三种岩石进行不同应变率下的冲击载荷破坏实验,同步采集破坏过程的声发射参数,从应力—应变、幅值分布、振铃计数变化以及峰值频率分布等方面进行了分析与研究。实验结果表明:力学特性方面,随着应变率增大,三种岩石的动态强度随之增大,极限应变也随之增大,且岩石试样的破碎程度随之增大,表现为碎块的尺寸减小、块数增加、碎屑增多。在声发射特性方面,三种岩石的峰值频率主要在550 k Hz以下,且随着应变率的增加,三种岩石的振铃计数都随之增大,低幅值信号比例增加,峰值频率在100 k Hz以下的低频信号随之减少,100~200k Hz以及400~550 k Hz的中高频信号随之增多,说明峰值频率有向中高频移动的趋势。

To study the acoustic emission （AE） characteristics of rock under impact loading conditions,the Split Hopkinson Pressure Bar （SHPB） system was adopted to carry out the impact loading tests. The acoustic emission pa- rameters of the failure process were collected synchronously, and analyzed from the aspects of stress-strain, amplitude distribution, cumulative ringing count and peak frequency distribution. The results showed that under the impact load of the test, the dynamic strength, ultimate strain, and rupture scale of three rocks all increase with increasing strain rate ,which shows that the fragment reduces in size and increases in number. In terms of acoustic emission character- istics, the peak frequency of three rocks were mainly distributed below 550 kHz. With the increase of strain rate, the ring down count of three rocks and the percentage of small amplitude signals increased, while the percentage of sig- nals with low peak frequency below 100 kHz decreased, and the percentage of signals with intermediate and high peak freauencv between 100 - 200 kHz and 400 - 550 kHz increased.