Micro-structure characteristics and dynamic mechanical properties of granite after hightemperature

In order to study the changes of mineral composition, micro-structure evolution characteristics and their relationship with dynamic mechanical properties of granite after high temperature, 20-1 000 degrees C high temperature tests were carried out based on the Beishan granite from Gansu Province. Microscopic images of granite after high temperature treatment were obtained by means of slicing technique and polarizing microscope. The evolution of mineral composition, mineral content and micro-structure characteristic parameters of granite with temperature were studied through mineral composition analysis, micro-cracks characteristic identification and parameters calculation. Subsequently, dynamic impact compression tests of high temperature treated granite were carried out by split Hopkinson pressure bar (SHPB) system, to analyze the effects of temperature, impact rate and micro-structure characteristics on dynamic peak stress. On this basis, the quantitative relationship between micro-structure characteristics and macroscopic dynamic mechnical properties was established. The results show that high temperature has a significant effect on the mineral composition, micro-structure and impact compression peak stress of granite, and 600 degrees C is taken as the threshold temperature. The impact rate also significantly affects the impact compressive strength, and the higher the impact rate, the less the influence of temperature on the macroscopic dynamic mechanical properties. The evolution of the micro-structure of granite after high temperature is the internal mechanism of the changes of its macroscopic dynamic mechanical properties with temperature. The characteristics of micro-cracks are significantly correlated with the dynamic peak stress, and the average width of cracks is the main factor affecting the dynamic peak stress of granite.