地质科技通报 (Mar 2023)
Experiment research of the influence of different cooling times on the drillability of high-temperature granite
Abstract
To study the drillability and microscopic damage changes of granite after high temperature exposure and to study the influence of different cooling times on drillability after high temperature exposure, granite for high-temperature heat treatment was cooled by different times (2 h, 4 h, 24 h, and 48 h). Through the drillability experiment and the cast thin identification of the processed rock samples, the influence law and mechanism of high temperature on the drillability of granite were obtained, and the influence of different cooling times on the granite drillability was also investigated. The research results show that granite always maintains a high drillability index under the constraints of heat treatment not exceeding 500℃ and natural cooling for 2 h. After cooling 4 h, 24 h, and 48 h, the impact of high temperature on drillability shows three stages (First degradation stage, strengthening stage, second degradation stage). The location and number of microcracks affect the difficulty of rock resistance to crushing. After 400℃ heat treatment, the internal microcracks of the granite begin to increase significantly. When the microcracks generate a large number of microcracks inside the quartz particles, the drillability of the granite is significantly reduced. After heat treatment at 100℃, cooling for no more than 4 h at the same time will significantly affect the drillability of granite. After heat treatment at 200-400℃, the drillability index of granite will increase significantly as the cooling time (4-48 h) continues to increase. The damage caused by 500℃ to granite is irreversible, and 600℃ has completely degraded the granite. Understanding the influence of high temperature and cooling time on the drillability of granite can provide basic theoretical support for the efficient exploitation of hot dry rock resources.
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