Current researches on acoustic emission test of rock are mostly focused on the mechanical properties of rock,and the acoustic emission test of rock brittleness is relatively a few.The uniaxial test and acoustic emission tests were carried out on four kinds of rock samples with different brittleness which are cement mortar rocks with different sand ratio,so as to obtain the stress-strain curves and the acoustic emission count curves.The result shows that the sand ratio of samples is positively related with rock brittleness.The greater the rock brittleness is,the greater the slope of the elastic deformation section is,the faster the stress drops and the larger the strain is after the peak on the stress-strain curves.On the acoustic emission count curves,the more brittle the rock sample is,the earlier the time that acoustic emission signal appears and the greater the maximum value of the acoustic emission count is.The acoustic emission count curves before the peak show that with the increase of rock brittleness,the fracture mode of samples transits from progressive fracture to burst fracture,and the fracture morphology of samples is changed from tensile crack to shear crack and mixed cracks.Overall,rocks with different brittleness have different acoustic emission characteristics,so acoustic emission characteristics can be used to judge the rock brittleness.This test result has theoretical reference value and practical significance for the evaluation of rock brittleness and hydraulic fracturing scheme design.%目前针对岩石声发射的试验主要集中在研究岩石的力学特性方面,关于岩石脆性的声发射试验相对较少.为了研究岩石脆性的声发射特征,对4种不同脆性的岩石试样进行了单轴压缩和声发射检测试验,所用试样为含砂比不同的自制水泥砂石,试验得到了试样的应力－应变曲线和声发射计数曲线.结果表明:试样中的含砂比与岩石脆性正相关;脆性越强,应力－应变曲线的弹性变形段斜率越大,峰后应力跌落越快,形变量越大,出现明显声发射信号的时间越早,声发射计数的最大值越大;峰前声发射计数曲线显示,随着岩石脆性的增加,试样破裂方式由渐进式破裂向突发式破裂过渡,裂缝形态由张性裂缝向剪性裂缝及混合裂缝转变.整体而言,岩石脆性不同,声发射特征也不同,根据声发射特征可以判断岩石脆性的强弱.该试验结果对于评价岩石脆性及水力压裂选层方案设计等具有理论参考价值和现实意义.
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