不同围压下页岩声发射及破裂前兆信息研究

对页岩进行常规三轴压缩下的声发射试验,并以时间为参考变量,得到力学与声发射参数之间的耦合关系,对其进行分析,以研究常规三轴压缩下页岩声发射特征的围压效应及其破裂前兆信息,并进一步揭示岩石破坏的微观机制,结果表明:(1)页岩声发射信号可分为4个阶段,即:原生裂纹压密阶段、平静阶段、爆发阶段、破坏阶段。(2)随着围压的升高,页岩的峰值强度随之升高,损伤强度σcd也随之升高,并且其数值约为峰值强度的91%。(3)随着围压的升高,由于破裂后的岩块之间的破裂面在凹凸处存在相互啮合啃断,岩样声发射信号在峰后残余强度阶段出现多个峰值。(4)页岩声发射RA值在主破裂发生前都有突然增大,并达到峰值的现象,预示着主破裂即将发生,因此可以将声发射RA值的突然增加作为页岩主破裂前兆信息。

Research on Confining Pressure Effect on Acoustic Emission of Shale and Its Main Fracture Precursor Information

In order to study the confining pressure effect on shale acoustic emission characteristics and shale main fracture precursor information under conventional triaxial compression condition, the corresponding acoustic emission experiments were conducted. With time as the reference variable, the micromechanism of rock damage was obtained through the analysis of the coupling relationship between mechanical and acoustic emission parameters. The results show that: (1) the acoustic emission signal of shale can be divided into four stages: native crack compaction stage, clam stage, explosion stage, and damage stage.(2) with the increase of confining pressure, shale peak strength and damage strength (σcd)increase and the value of damage strength is about 91% of the peak strength.(3) with the increase of confining pressure, acoustic emission signal appear multiple peaks after rock fracture because of the intermeshing in the bulges and concavities of fracture face.(4) shale acoustic emission RA value before the main fracture suddenly increase, and reach to the peak value, indicating that the main rupture is about to happen. Therefore it can take the increase of RA value as the precursor information of shale main rupture.