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利用RMT-150B岩石力学试验机对煤样进行三轴循环加卸载试验,对三轴循环加卸载条件下煤样的变形及强度特征进行分析。结果表明:在三轴循环加载过程煤样的变形表现出明显记忆性,循环加载过程的应力-应变外包络线与连续加载的应力-应变曲线相吻合。在煤样屈服前进行加卸载,加载时弹性模量始终低于卸载时的弹性模量,且随加卸载次数的增加,加卸载时的弹性模量均有小幅增加,过峰值后弹性模量与峰值前弹性模量相比有所减小,但仍高于第1加载的弹性模量。三轴压缩条件下煤样的峰值强度、残余强度与围压成正比,符合Coulomb强度准则。峰值强度、残余强度与围压回归得到的摩擦系数大致相当,黏聚力则减低54.4%。
The RMT-150B rock mechanics testing machine was used to carry out three-axis cyclic loading and unloading tests on coal samples. The deformation and strength characteristics of the coal samples under three-axis cyclic loading and unloading conditions were analyzed. The results show that the deformation of coal sample shows obvious memory during cyclic loading, and the stress - strain outer envelope of cyclic loading coincides with the stress-strain curve of continuous loading. Unloading before coal yielding, the elastic modulus at loading is always lower than unloading elastic modulus, and with the increase of loading and unloading, loading and unloading of the modulus of elasticity have a slight increase in the peak after the elastic modulus Decreased compared to the pre-peak elastic modulus but still higher than the first-loaded elastic modulus. Under triaxial compression, the peak strength and residual strength of coal samples are proportional to the confining pressure and meet the Coulomb strength criterion. The peak strength and residual strength are approximately the same as those obtained by the confining pressure regression, while the cohesion decreases by 54.4%.