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Rock and Soil Mechanics

Abstract

In order to study the change rules of mineral composition, micro-structure evolution characteristics and their relationship with dynamic properties of granite after high temperature treatment, the high temperature tests on Beishan granite in Gansu Province, China, were carried out at 20−1 000 ℃. Microscopic images of granite after high temperature treatment were obtained by 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 properties was established. The results show that high temperature has a significant effect on the mineral composition, micro-structure and impact compressive strength of granite, and 600 ℃ is taken as the threshold temperature. The loading rate also significantly affects the impact compressive strength, and the larger the loading rate is, the less the influence of temperature on the macroscopic dynamic properties is. The evolution process of the micro-structure of granite after high temperature treatment is the internal mechanism for the change of its macroscopic dynamic properties with temperature. The microcrack characteristics have a significant correlation with the dynamic peak stress, and the average crack width is the main factor affecting the dynamic peak stress of granite.

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