花岗岩板渐进破坏过程的微观研究

研究了花岗岩板在单轴压缩应力状态下的微观破坏过程。试验主要采用了液压加载台、光学显微镜、同步录象系统以及二次复型技术等。研究发现，花岗岩原开裂是局部发生的，并首先开始于石英颗粒的边界，而这些边界多数位于近轴向。轴向裂纹的发生和发展最终导致样品的劈裂破坏。不同的矿物颗粒表现各自特有的、与其微观结构密切相关的破坏行为。石英在花岗岩的破坏过程中起着极其重要的作用。表面裂纹的分形维数随破坏的发展而持续增加直到样品突然失稳。

PROGRESSIVE CRACKING OF GRANITE PLATE UNDER UNIAXIAL COMPRESSION

Progressive cracking of granite plate under uniaxial compression had been investigated by using a loading frame,which could be well equipped with optical microscope and video recorder. For revealing the details of the process at mineral grain level,a double replica technique had been employed to copy the mineral grains and the crack patterns on the specimen surface. Based on these replicas,observation study on the failure behavior of different minerals and fractal analysis on the crack patterns can be carried out. It is found that the cracking of granite appears locally and begins with the opening of quartz grain boundaries,which are nearly located in the compressive direction. Different minerals present their distinct behaviors during failure,which are believed to depend on their microstructure natures. The cracks developing in loading direction are dominant under uniaxial compression. Their propagation and coalescence finally result in the splitting failure of the specimen. Quartz acts as a crucial mineral to mainly control the failure of granite. The fractal dimension of surface crack pattern increases continuously with the cracking development before the final collapse takes place.