为揭示岩石破坏机制,通过蚀变花岗片麻岩单轴压缩声发射实验,分析岩石破裂过程中平均频率及上升角度倒数的变化规律,并依据其分布特征研究裂纹的破裂类型、拉伸与剪切裂纹所占比例的变化情况.结果表明:平均频率在岩石受力过程中出现上升-下降-波动的变化趋势,而上升角度倒数在岩石受力过程中出现小幅波动-突增-波动的变化趋势.平均频率明显下降及上升角度倒数的突增可作为岩石处于较高应力水平的标志.剪切裂纹所占的比例随着应力的增加呈先降低再升高的趋势.在岩石破坏前,剪切裂纹的比例出现突增,最高可超过50%.该研究可为岩石破坏前兆的判断提供可靠依据.%This paper introduces an effort to investigate the acoustic emission( AE) precursors of rock failure. The research effort consists of performing AE tests on altered granite gneiss under the condition of uniaxial compression;analyzing the change laws underlying the average frequency and the reciprocal of rise angle during the rock failure process, using sliding window method; determining the crack type by the average frequency and the reciprocal of rise angle; and ultimately identifying the change law behind the proportion of tensile and shear cracks. The study demonstrates that the process of rock force sees an average frequency varying from rise and fall to fluctuation, accompanied by a tendency to slightly fluctu-ate, drastically ascend, and fluctuate in the reciprocal of rise angle; the drastic decrease of the average frequency and the drastic increase of reciprocal of rise angle can be indicative of rocks in s high stress level;with the increase of stress comes an initial increase and a subsequent decrease in the proportion of shear cracks;and the rock failure is preceded by a sharp increase in the proportion of shear cracks, an increase of more than 50%. The combined analysis of the average frequency, reciprocal of rise angle, and fracture type can provide a reliable basis for judging rock failure precursor.
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