热损伤粗粒花岗岩强度与变形破裂特性试验研究

Experimental study on strength and deformation fracture characteristics of coarse granite with thermal damage

为了研究热损伤粗粒花岗岩强度与变形破裂特征,采用MTS815试验机开展了三轴压缩试验,探讨不同条件下热损伤粗粒花岗岩物理参数、力学参数和破坏特征的演化规律,分析各个试验条件下的声发射特征。研究结果表明:当热处理温度超过400℃时,岩样质量、密度、纵波波速下降和体积增大的趋势更明显;随着热处理温度增加,峰值强度和弹性模量随温度升高呈指数规律减小,峰值应变和泊松比随温度升高总体呈增大趋势;围压会抑制裂纹扩展,使得岩石的宏观力学参数(E,σ_(c),μ和ε_(p))随围压增大而增大,但增大到一定程度(15 MPa)后变化幅度越来越小;基于Mohr-Coulomb准则得到的黏聚力随温度变化在200℃处最大(25.07 MPa),内摩擦角受温度影响不明显;温度和围压增加会增强岩石的塑性变形能力,岩样破坏角与理论破裂角45°+φ/2相近,其受围压的影响大于温度的影响;随温度增加,声发射振铃数缓慢增加;围压越大、温度越高,峰后段声发射越活跃,但温度效应更明显。

In order to study the strength and deformation fracture characteristics of thermal-damaged granite,triaxial compression tests were carried out using MTS815,the evolution laws of physical parameters,mechanical parameters and failure characteristics of thermal-damaged granite under different conditions were discussed in detail,and the acoustic emission characteristics under various test conditions were analyzed.The results show that mass,density,and P-wave velocity decrease,but volume increases once the temperature is higher than 400℃.With the increase of heat-treating temperature,the peak strength and elastic modulus decrease following a negative exponential function,and the peak strain and Poisson's ratio increase.The increasing confining pressure enhances the macro-mechanical parameters,i.e.E,σ_(c),μ and ε_(p),due to the constrain effect in the crack growth.Once confining pressure increases to certain values(15 MPa),the increasing amplitude gradually decreases.The cohesion strength reaches the maximum value of 25.07 MPa at about 200℃.However,the friction angle is not significantly affected by temperature.The plastic deformation is also enhanced with increasing temperature and confining pressure.The failure angle of rock sample is close to the theoretical value of 45°+φ/2,and the influence of confining pressure is greater than that of temperature.The acoustic emission(AE)ring number gradually increases with increasing temperature.Meanwhile,the AE events become active when the confining pressure and temperature are higher,but the temperature effect is more obvious.