高温三轴应力下大理岩损伤演化与声发射活动特征研究

Acoustic emission activity and damage evolution characteristics of marble under triaxial stress at high temperatures

为了揭示温度影响下的大理岩裂隙发展与损伤演化规律,利用岩石高温三轴伺服试验机与声发射测试系统,研究了30、60、90、120、150℃条件下的大理岩变形破坏特征与声发射活动规律。研究结果表明,高温作用下大理岩三轴压缩破坏经历压密和弹性变形阶段、塑性变形阶段、延性破坏阶段以及失稳破坏阶段共4个阶段,且试验温度越高,压密变形阶段和延性破坏阶段历时越长,岩石由弹脆性破坏逐步向弹塑性破坏转化。大理岩峰值强度、弹性模量和内摩擦角随温度升高而降低。岩石的声发射活跃度和声发射定位与宏观裂纹的对应性随试验温度的升高而降低。分析大理岩损伤演化过程的声发射信号幅值、撞击、振铃计数、声发射能量、峰值频率和b值特征发现,声发射幅值波动较小、温度敏感性较差,峰值频率和b值参数可以较好地表征岩石内部的裂纹发展情况,且峰值频率的温度敏感性最佳,可优选作为岩石破裂失稳的预测指标。三轴压缩破坏过程中大理岩产生张剪复合裂纹,并以剪切裂纹占主导,高温抑制了岩体内部裂纹的萌生,试验温度越高,岩石的张拉破坏越弱、剪切破坏越强。该研究成果为揭示岩石热损伤机制及工程热害预报提供了参考。

In order to reveal the fracture development and damage evolution law of marble under the influence of temperature,the deformation and failure characteristics and acoustic emission activity of marble under the conditions of 30,60,90,120℃and 150℃were studied by using triaxial servo testing machine and acoustic emission testing system.The results show that the triaxial compression failure of marble under high temperature goes through four stages:compaction and elastic deformation stage,plastic deformation stage,ductile failure stage and instability failure stage.The higher the test temperature is,the longer the compaction deformation stage and ductile failure stage are,and the rock gradually transforms from elastic brittle failure to elastic-plastic failure.The peak strength,elastic modulus and internal friction angle of marble decrease with the increase of temperature.The acoustic emission activity of rock and the correspondence between AE location and macroscopic crack decrease with the increase of test temperature.By analyzing the characteristics of acoustic emission signal amplitude,impact,ringing count,acoustic emission energy,peak frequency and b value in the damage evolution process of marble,it is found that the amplitude fluctuation of acoustic emission is small and the temperature sensitivity is poor,but the peak frequency and b value parameters can better characterize the crack development inside the rock.The peak frequency has the highest temperature sensitivity,which is favorable as the prediction index of rock failure and instability.In the process of triaxial compression failure,tension-shear composite cracks appear in marble,of which shear cracks are dominant.High temperature inhibits the initiation of internal cracks in rock mass.The higher the test temperature is,the weaker the tensile failure and the stronger the shear failure are.The test results shed light on the study of rock thermal damage mechanism and engineering thermal damage monitoring and prediction.