高温作用下花岗岩的声发射特征研究

 通过MTS810材料测试系统及AE21C声发射检测仪对山东临沂花岗岩在20 ℃～800 ℃单轴压缩下的声发射特征进行试验研究，分别分析升温过程中花岗岩振铃计数率随时间的变化规律以及加载过程中花岗岩的声发射特征参量与应力–应变之间的关系。研究表明：升温及加载过程中，花岗岩声发射振铃计数率随着温度升高而增大，声发射活动也变得更频繁；其声发射参量在400 ℃～800 ℃高温后与高温下有较大差别，高温后的声发射参量明显低于高温下，岩样内部裂纹较少以致高温后花岗岩的强度等力学指标要优于高温下；各温度段高温下声发射振铃累计数都要高于高温后，尤其在800 ℃时，两者相差超过1倍；800 ℃前花岗岩岩样主要呈劈裂和剪切破坏为主的脆性破坏，未出现强烈的塑性破坏；高温使储存的能量显著增多并加速能量耗散，能量的耗散和弹性能的释放使岩石的强度减小，宏观裂纹增多并最终破坏。

RESEARCH ON ACOUSTIC EMISSION CHARACTERISTICS OF GRANITE UNDER HIGH TEMPERATURE

The laboratory tests are made for studying characteristics of acoustic emission(AE) of granite from Linyi in Shandong province at 20℃ to 800℃ using hydraulic-pressure servo testing system MTS810 and acoustic emission instrument AE21C. The relationship between ringdown count rate of granite and time as well as the relationship between AE parameters and stress-strain curves due to uniaxial compression loading are analyzed under different temperatures. Studies have shown that ringdown count rate rises and AE activity becomes more frequent with temperature increases both in the processes of heating and loading. AE parameters are quite different at and after the high temperature，of which AE parameters after high temperature are significantly lower than that at high temperature；and internal cracks are fewer resulting in that mechanical properties at high temperature are superior to that after high temperature. Ringdown cumulative count of granite at high temperature is higher than that after high temperature；especially at 800 ℃ when there is more than a doubled difference. The high temperature causes a significant increase in energy and accelerating the energy dissipation. The granite specimens showed brittle failure such as splitting and shear failure which did not appear strong ductile failure. The strength of the rock decreases and macroscopic cracks increase due to energy dissipation and elastic energy release which eventually cause deformation and failure of granite.