单轴压缩条件下预制裂纹红砂岩试样声发射特征研究*

为研究单轴压缩条件下预制裂纹红砂岩试样声发射特征，运用伺服压力机、声发射系统对砂岩试样进行单轴压缩试验，结合声发射特征参数与应力时间关系，对砂岩试样变形失稳破坏过程进行分析，并在相同加载方式下分析不同裂纹角度对砂岩试样变形破坏特征的影响。结果表明:砂岩试样破坏过程按力学性质可分为压密、弹性变化、塑性变化及峰后残余4个阶段，预制裂纹对试样的峰值应力有显著降低作用；声发射信号可分为平静期、上升期、波动期3个阶段，信号与砂岩试样破坏过程存在良好对应关系，不同角度预制裂纹对应的声发射信号特征不同，平静期45°裂纹试样声发射事件相对较活跃，振铃累积率相对最高，0°裂纹试样最早进入声发射波动期；在相同加载方式下，声发射信号参数RA值受裂纹角度影响较大，可以利用声发射信号RA值的演化判断岩石材料中裂纹方向与荷载方向的关系。

Study on AE characteristics of red sandstone samples with prefabricated crack under uniaxial compression

In order to study the acoustic emission characteristics of red sandstone specimens with prefabricated crack under the uniaxial compression,the uniaxial compression tests were conducted on the sandstone specimens by using the servo press and the AE system.Combined with the relationship between AE characteristic parameters and stress time,the deformation instability and failure processes of sandstone specimens were analyzed,and the influence of different crack angles on the deformation and failure characteristics of sandstone specimens under the same loading mode was analyzed.The results showed that according to the mechanical properties,the failure process of sandstone specimens could be divided into four stages,including the compaction stage,elastic change stage,plastic change stage and post-peak residue stage,and the prefabricated crack could significantly reduce the peak stress of the specimens.The AE signals could be divided into three stages,including the quiet period,rising period and fluctuation period,and there was a good corresponding relationship between the signal and the failure process of sandstone specimens.The AE signal characteristics corresponding to the prefabricated cracks with different angles were different.In the quiet period,the AE events of specimens with 45° crack were more active,the ringing accumulation rate was the highest,and the specimens with 0° crack was the first to enter the AE fluctuation period.Under the same loading mode,the RA value of AE signal parameter was greatly affected by the crack angle,and the evolution of RA value of AE signal could be used to judge the relationship between crack direction and load direction in the rock material.