基于巴西劈裂试验的岩石声发射特性及断口特征分析

为综合研究岩石在拉伸状态下的破裂机理,对花岗岩、灰岩、砂岩、大理岩4种岩石进行巴西劈裂试验,采用PCI-2声发射仪采集试样破裂全过程的声发射信号,利用扫描电镜研究试样断口的微观结构,并探讨了岩石破裂声发射信号与断口微观特征之间的关系。试验结果表明:岩石破裂声发射信号的特征与断口微观特征可联合表征岩石在劈裂荷载下的破坏机理。在劈裂荷载下,岩石破裂产生的声发射信号的累计振铃计数呈稳定增长期、突增期、平静期3个阶段,且峰值频率呈带状分布,分别集中于0~50kHz,100~150kHz及300kHz上下3个频率段;岩石断口微观特征为典型的脆性拉伸断口样貌,且断口花样的复杂程度与振铃计数率呈正相关,断口破裂尺度与峰值频率呈负相关。

Acoustic emission parameter characteristics and fracture morphology analysis of rocks based on Brazilian splitting test

To comprehensively study the fracture mechanism of rock in tensile state,the Brazilian splitting tests of granite,limestone,sandstone and marble are carried out,and a PCI-2 acoustic emission(AE)instrument is used to collect the AE signal of the whole process of sample fracture.The microstructures of fracture are further studied by the scanning electron microscopy(SEM).Finally,the relationship between AE signal of rock fracture and microscopic characteristics of fracture is discussed.The experimental results show that the characteristics of AE signals and the fracture morphology can jointly represent the failure mechanism of rocks under splitting loads.In this situation,the cumulative ringing counts of AE signals can be divided into three stages,including the steady increase period,the sudden increase period and the quiet period.The peak frequency shows a zonal distribution feature which distributes in the intervals of 0~50kHz,100~150kHz and around 300kHz,respectively.The microscopic characteristics of rock fracture indicate typical brittle tensile fracture morphology,and the complexity of microscopic fracture patterns are positively correlated with the ringing count rate,while the fracture scale is negatively correlated with the peak frequency.