Abstract:
In order to investigate the influences of temperature and dynamic loading on the failure mechanism of biotite granite, the cyclic impact compression tests on the granite specimens heat-treated by different temperatures were carried out using the split Hopkinson pressure bar. The tungsten-filament scanning electron microscope was used to observe the fracture morphology of the specimens. The results show that at room temperature the ductile fatigue cracks appear on the fracture surface under the low impact velocity and brittle fatigue cracks are turned out under the action of the middle impact velocity. However, the typical cleavage cracks appear on the fracture surface under the high impact velocity. Under the same impact loading, there are a large number of cleavage cracks and wallner lines on the fracture surface of the rock specimens below 400 ℃ heat treatment temperature. With the increase of the heat treatment temperature, the number of the cleavage cracks decreases, and many quasi-cleavage fractures and dimples gradually increase. Under cyclic impact loading, the loading-rate effect of the granite is obvious, that is, the higher the impact velocity, the more obvious the brittle fracture characteristics is. Meanwhile, the temperature effect makes the ductility of the granite significantly enhanced, and an increase in the heat treatment temperature will lead to the transition of the failure mode of the granite specimens from the brittle fracture to the brittle-local ductile fracture.