不同饱水度花岗岩的真三轴岩爆试验研究

True triaxial test on rockburst of granites with different water saturations

利用真三轴岩爆试验系统,开展了不同饱水度红色粗晶花岗岩的岩爆试验,分析了不同饱水度下岩爆破坏岩样的强度与变形特征、破坏与弹射特征、声发射特性等,探讨了岩石饱水度与岩爆弹射动能的定量关系以及水对岩爆的影响机制。研究结果表明:(1)当岩样的相对饱水度超过0.3,其峰值应力和屈服应力较天然状态的明显降低;(2)岩样饱水度的增加使得岩爆过程中小颗粒弹射减少、小岩片剥落增多、岩板外鼓现象减弱,且岩爆坑体积减小、岩爆碎块的粒径分布由连续分布变为不连续分布;(3)随饱水度的增加,岩爆发生前夕声发射撞击数显著下降的平静期的总历时呈缩短趋势,岩爆发生时刻的声发射撞击数呈增大趋势,且累积绝对能量呈减小趋势、能量释放速度呈放缓趋势,表明岩样塑性破坏特性有所增强;(4)岩爆弹射动能随饱水度的增大而显著减小,二者呈单调线性的负相关关系,水对岩石的作用主要是软化和水楔作用,水的黏性也会对碎块弹射产生影响。

The rockburst experiments were conducted on red coarse-grain granites with different water saturations by using true triaxial rockburst test system.Then this study analyzed the characteristics of strength and deformation,damage and ejection process,failure mode and acoustic emission(AE)of rock specimens after rockburst with different water saturations.The relationship between the water saturation and kinetic energy of rockburst ejection and the influence mechanism of water on rockburst were discussed as well.The results showed that when the water saturation of specimens exceeded 0.3,the peak stress and yield stress of the specimens were significantly lower than those of natural specimens.With the increasing of water saturation,the ejecting behavior of small particles decreased,the spalling behavior of small rock slices increased,and the bulging behavior of rock plates weakened during the process of rockburst.Moreover,the volume of rockburst pits decreased,and the particle-size distribution of rockburst fragments became discontinuous.With the increasing of water saturation,the duration of‘quiet period’decreased,in which AE impact number dropped significantly before rockburst.Besides,the AE impact number increased at the moment of rockburst,while the accumulated absolute energy and the energy release rate declined,which indicated that the plastic failure of specimen enhanced.The rockburst kinetic energy of specimens decreased obviously with the increasing of water saturation,which exhibited a monotonous linear relationship between the kinetic energy and water saturation.Water mainly showed softening and water wedge effects on rock,and the viscosity of water also affected the ejection of rock fragments.