Macroscopic and microscopic experimental research on granite properties after high-temperature and water-cooling cycles

•High-temperature and water-cooling cycles influence the micro-structural and mechanical behaviours of granite.•The crack rate and main crack aperture are used to quantify the microcrack evolution.•The coupling of inhomogeneous expansion, cyclic thermal shock and water-induced weakening leads to the...

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Bibliographic Details
Published in:Geothermics 2021-06, Vol.93, p.102079, Article 102079
Main Authors: Zhang, Bo, Tian, Hong, Dou, Bin, Zheng, Jun, Chen, Jie, Zhu, Zhennan, Liu, Hengwei
Format: Article
Language:English
Subjects:
Compressive strength
Cooling
Cyclic water cooling
Damage
Deterioration
Drilling
Experimental research
Geothermal power
Granite
High temperature
High-temperature granite
Liquid cooling
Mechanical properties
Microscopical characteristics
Minerals
Modulus of elasticity
P waves
Rocks
Thermal cycling
Thermal shock
Ultrasonic methods
Velocity
Void space
Wave velocity
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Summary:•High-temperature and water-cooling cycles influence the micro-structural and mechanical behaviours of granite.•The crack rate and main crack aperture are used to quantify the microcrack evolution.•The coupling of inhomogeneous expansion, cyclic thermal shock and water-induced weakening leads to the damage of granite.•Different cyclic cooling methods are compared and analysed.•Relations between Vp, UCS and E after different high-temperature and water-cooling cycles are found. During drilling, reservoir fracturing and hot dry rock development, high-temperature rock is subjected to cyclic water cooling. The mechanical properties and microscopic characteristics of granite exposed to high-temperature and water-cooling cycles were investigated experimentally. The results show that the uniaxial compressive strength and elasticity modulus decrease with increasing temperature and cycles, especially above 400 °C and after 1 cycle. In addition, the P-wave velocity decreases continuously and rapidly with temperature and it drops dramatically after 1 cycle and then more slowly with increasing cycles. The inhomogeneous expansion of minerals and cyclic thermal shock are the essential reasons for rock deterioration. The decay of elasticity modulus and enlargement of void space stops the damage to granite from being aggravated after a certain number of cycles. There is a good correlation between the P-wave velocity and mechanical parameters, and the damage factor based on the uniaxial compressive strength and elastic modulus has a positive correlation with the damage factor obtained by the ultrasonic method, illustrating that the ultrasonic method can be utilized to reflect the changes in mechanical characteristics.
ISSN:0375-6505
1879-3576
DOI:10.1016/j.geothermics.2021.102079