周期荷载作用下白砂岩的疲劳特性研究

INVESTIGATION ON FATIGUE CHARACTERISTICS OF WHITE SANDSTONE UNDER CYCLIC LOADING

利用RMT–150B岩石力学试验系统,分别采用固定下限应力改变上限应力和固定上限应力改变下限应力的试验方法,进行不同加载条件下白砂岩的疲劳试验,研究周期荷载作用下白砂岩疲劳破坏过程中的疲劳特性、轴向应变的累积规律和轴向不可逆变形的发展规律和应变速率与循环次数的关系。研究结果表明,周期荷载作用下白砂岩的破坏过程宏观上是轴向不可逆变形的逐步发展累积,直到其破坏的过程,且其轴向不可逆变形发展过程表现出不依赖于应力比的三阶段发展规律;且疲劳破坏过程受静态应力–应变全过程曲线的控制,周期荷载的上限应力和振幅是影响白砂岩疲劳破坏过程和疲劳寿命的主要因素。

Using rock mechanics test equipment RMT- 150B, utilizing two different test methods--one is changing the maximum of cyclic load with the minimum of cyclic load fixed and the other is changing the minimum of cyclic load with the maximum of cyclic load fixed. The fatigue characteristics, the axial strain accumulation rule and the irreversible deformation development law and the relations betweens the axial strain rate and the cyclic numbers of times of white sandstone under the different cyclic loading conditions are studied. The results show that the macroscopic process of white sandstone fatigue failure under cyclic loading is the development of irreversible axial deformation, which finally leads to destruction of rock sample and exhibits three development phases that don＇t depend on cyclic loading conditions. The fatigue failure curve of white sandstone is controlled by its complete stress-strain curve under static loading. The amplitude and the maximum of cyclic load are the most important factors influencing the process of fatigue failure and fatigue lifespan of white sandstone.