冻融作用下裂隙岩石损伤破坏声发射特性研究

Research on acoustic emission characteristics of fractured rock damage under freeze-thaw action

为探究冻融环境对露天煤矿边坡稳定的影响,本文以饱和裂隙红砂岩为对象,开展冻融后单轴压缩声发射特性试验,分析不同冻融次数和裂隙倾角对岩石宏观力学特性和声发射参数特征的影响,研究损伤过程中b值和损伤变量演化规律。结果表明:冻融循环和裂隙倾角的变化对岩样应力-应变曲线有较大影响。岩样峰值强度与冻融次数呈负相关性,与双裂隙倾角呈正相关性。轴向应力突降点与声发射振铃计数峰值相互吻合。冻融循环次数的变化引起加载初期振铃计数增大。声发射三维事件点的数量和分布与裂隙倾角密切相关。声发射b值整体保持上下波动状态,冻融循环使b值初期波动减缓。裂隙倾角的增大引起b值在应力最高处更加密集。裂隙岩石的损伤过程分为3个阶段:初始损伤累积阶段、损伤加速阶段和最终破坏阶段,冻融循环加速了岩样的初始损伤累积。裂隙倾角越大,损伤加速阶段的斜率越大。该研究可为寒区露天煤矿边坡稳定提供理论基础。

In order to study the effects of freezing and thawing environment on the slope stability of opencast coal mines,this paper takes saturated fractured red sandstone as the object,experiments on acoustic emission characteristics under uniaxial compression after freezing and thawing are conducted.The effects of different freeze-thaw times and fracture dip angle on the macroscopic mechanical properties and acoustic emission parameters of rock are analyzed.The evolution law of b value and damage variables in the damage process are studied.The results show that the freeze-thaw cycles and the change of fracture dip angle have a great influence on the stress-strain curves of the rock samples.The peak intensity of rock samples has a negative correlation with freeze-thaw times,and a positive correlation with double fracture dip angle.The point of axial stress dip coincides with the peak value of the acoustic emission ringing count.The change in the number of freeze-thaw cycles caused the ringing count to increase at the initial stage of loading.The number and distribution of acoustic emission three-dimensional event points are closely related to the dip angle of fracture.The b value of acoustic emission keeps fluctuating up and down as a whole,and the initial fluctuation of b value is slowed down by freeze-thaw cycles.The increase of the fracture dip angle of the fracture causes the b value to be more dense at the highest stress point.The damage process of fractured rock can be divided into three stages:initial damage accumulation stage,damage acceleration stage and final failure stage.Freeze-thaw cycles accelerate the initial damage accumulation of rock samples. The slope of damageacceleration phase increases with the increase of fracture dip angle. The results of this paper can providetheoretical basis for the slope stability of opencast coal mines in cold regions.