外荷载下青砂岩声发射特征及损伤演化规律

Acoustic Emission Characteristics and Damage Evolution of Green Sandstone Under External Loads

为分析青砂岩(QSY)在外荷载下的声发射特征及损伤演化规律,在声发射基础上,根据岩石损伤演化的自组织性、丛集行为及幂律分布特性,结合砂岩结构特征、分形理论和Weibull分布函数,建立了青砂岩损伤二维元胞模型。结果表明:青砂岩试样在荷载后期的塑性变形阶段轴向应力曲线发生线性突变是试样发生破坏的最终结果,破坏值为48.5 MPa,该阶段因微裂隙贯通形成大裂隙,存在事件率缺失现象,该现象为试样破坏前兆特征,破坏方式主要为单斜面和双斜面剪切破坏,形成剪切裂纹;试样受载损伤的3个阶段与AE信号表现特征存在类同,在损伤萌生阶段试样因受矿山生产影响内部存在微缺陷,在此阶段形成损伤演化现象,但间隔损伤值为0.41,未达到所建立元胞模型的不稳定损伤值(0.43),未发生破坏;随着损伤值增大至0.599时(大于0.43),试样发生失稳破坏,损伤值快速增长至1。根据岩石损伤演化相关规律和理论建立的二维元胞模型,能够反映青砂岩在外荷载下受力破坏过程和损伤演化规律,为相关研究提供参考和借鉴。

As a micro-unit combination of geotechnical engineering,rock will be accompanied by complex AE signals and damage evolution characteristics during the loading process.In order to analyze the AE characteristics and damage evolution law of green sandstone under external load,a two-dimensional damage cell model of green sandstone was established based on acoustic emission,according to the self-organization,clustering behavior and power law distribution characteristics of rock damage evolution,combined with the structural characteristics of sandstone,fractal theory and Weibull distribution function.The results show that:The linear mutation of the axial stress curve of green sandstone sample in the plastic deformation stage at the late loading stage is the final result of the failure of the sample,and the failure value is 48.5 MPa.At this stage,large cracks are formed due to the combination of microcracks,resulting in the absence of event rate.This phenomenon is the precursor feature of the failure of the sample,and the main failure modes are single-bevel shear failure and double-bevel shear failure.The forming crack is shear crack.The three stages of loading damage of the sample are similar to the characteristics of AE signals.In the damage initiation stage,due to the internal microdefects of the sample affected by mine production,damage evolution will be formed at this stage,but the interval damage value is 0.41,which is lower than the unstable damage value of the established cellular model(0.43).No failure or instability failure occurs until the damage deformation stage.When the damage value increases to 0.599(greater than 0.43),instability failure occurs in the sample,and the damage value rapidly increases to 1.Therefore,it can be concluded that the two-dimensional cellular model established by the relevant laws and theories of rock damage evolution can reflect the mechanical failure process and damage evolution law of bluestones under external loads,which can provide reference for related studies.