单轴压缩条件下加锚砂岩声发射特性及其与岩爆的联系

Acoustic emission characteristics of anchored sandstone under uniaxial compression and its correlation with rockburst

为研究锚固岩体破坏机制,结合声发射监测技术,采用RMT-150C型试验系统开展加锚砂岩的单轴压缩试验,探讨单轴压缩下加锚砂岩声发射RA值(声发射信号上升时间与幅值的比值)特征及其对应的裂纹扩展演化和室内岩爆的联系。研究结果表明:无锚砂岩加载初期的声发射活动平静且持续时间长,加载后期声发射信号集中释放,加锚砂岩在加载初期迅速产生较高频率的声发射信号,声发射信号具有分散性释放的特点,无锚和加锚砂岩声发射振铃计数峰值和声发射能量峰值均在其外载荷接近峰值时出现;无锚砂岩和加锚砂岩最终破裂均为拉剪破坏,但无锚砂岩破裂演化初始为张拉裂纹,加载初期产生较高的声发射RA值,加锚砂岩破裂演化初始为剪切裂纹,加载初期产生较低的声发射RA值;声发射RA值与岩石破裂类型有极大相关性,其变化趋势与锚固作用有联系,能对锚杆支护措施下的岩爆灾害监测预警有较好的指导作用。

In order to study the instability mechanism of anchored rock mass, combined with acoustic emission(AE) monitoring technology, RMT-150 C test system was used to carry out the uniaxial compression test of anchored sandstone samples to discuss the acoustic emission characteristics of crack propagation and evolution and its correlation with rockburst. The results show that the AE activity of the sandstone sample without bolts occurs quietly in the initial stage of loading and its AE quiet period can last for a long time, and its AE signals are released centrally in the later stage of loading. For anchored sandstone samples, high frequency AE signals emerge rapidly in the initial stage of loading, and the whole process of AE signals shows the characteristics of dispersive release. For both kinds of sandstone samples, their peak values of AE ring count and AE energy occur when the uniaxial load is close to its peak value. All sandstone samples have the same final failure mode, namely tensileshear failure. Their significant difference is that the first visible tension crack of anchorless samples in the initial stage of loading appears accompanied by a high RA value of AE and anchored samples with a first visible shear crack are accompanied by a low RA value of AE. The RA value of AE is highly correlated with the type of rock fracture, and the change trend of its value can be influenced by the rockbolt, which can still provide reference for monitoring and early warning of surrounding rock disasters with anchor bolt support measures rockburst.