砂岩巴西劈裂疲劳破坏过程中变形与强度特征的试验研究

EXPERIMENTAL RESEARCH ON DEFORMATION AND STRENGTH CHARACTERISTICS IN PROCESS OF BRAZILIAN SPLIT FATIGUE FAILURE OF SANDSTONE

利用RMT-150B岩石力学多功能系统,对砂岩巴西劈裂疲劳破坏过程中的变形与强度特征进行试验研究。试验结果表明:常规劈裂试验峰值前的变形与单轴压缩的变形特征大致相同,可分为压密、弹性、屈服和破坏4个阶段;疲劳破坏完全受到常规劈裂全过程曲线的控制,破坏时的变形量与上限载荷(应力)在常规劈裂全过程曲线峰后对应的变形量相当;疲劳试验过程中的变形量(变形速率)与时间曲线类似蠕变特征曲线,可分为初期加速、等速和加速3个阶段;疲劳上限载荷(应力)比、抗拉疲劳强度与循环次数呈负相关,疲劳上限载荷(应力)比是影响岩石疲劳寿命主控因数,试样内部原微裂纹等缺陷分布特征对劈裂疲劳寿命影响显著;疲劳上限载荷(应力)比增加导致疲劳寿命降低,而破坏时拉伸变形基本保持不变。

The deformation rules and strength characteristics of sandstone samples in the process of Brazilian split fatigue load were studied by the RMT–150B multi-function servo system.The results showed that there were almost same deformation characteristics in both the conventional split test and uniaxial compression test before the peak load,which could also be divided into 4 stages including compression,elasticity,yielding and failure stage.The destroy mode of Brazilian split fatigue was controlled completely by the fracture process curve of the conventional Brazilian split;and the deformation value and upper limit load（stress） were equivalent to the corresponding deformation in the post-peak process curve of the conventional Brazilian split test.The deformation（rate） curve versus time in the process of splitting fatigue test was similar to the creep characteristics curve,which could be divided into 3 stages including initial acceleration,constant velocity and acceleration stage;and the fatigue limit load（stress） ratio and the tensile fatigue strength were negatively correlated with the cycle number.The fatigue upper limit load（stress） was the main control factor impacting the rock fatigue life;and the internal original microcrack distribution of sandstone sample had great influences on the split fatigue life.The increase of the upper fatigue limit load（stress） leaded to reductions in fatigue life;while the tensile deformation basically unchanged.