| Autor: |
Meng, Fanzhen, Han, Jianhua, Li, Zhiyuan, Wang, Feili, Yue, Zhufeng, Cai, Qijin, Cui, Guanghao, Zhou, Hui |
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| Zdroj: |
Rock Mechanics & Rock Engineering; Sep2024, Vol. 57 Issue 9, p6543-6566, 24p |
| Abstrakt: |
In deep tunneling and mining, high-level radioactive waste repositories, and geothermal reservoirs, the rock fractures are typically in the thermal–mechanical coupled condition. It is crucial to precisely replicate the geoenvironment in the lab, including stress, temperature, boundary conditions, and other factors, to derive trustworthy strength estimates for rock fractures. Utilizing the recently developed shear apparatus, we performed direct shear tests on rough granite fractures under thermal–mechanical coupled loading (room temperature to 400 °C, 1–30 MPa) to address the effects of normal stress and high in-situ temperature on the shear behavior of rough granite fractures, and the sequence of heating and normal loading on the strength parameters is also examined. Results show that the acoustic emission is more active if the fracture is heated under a large normal stress, while the expansion in the normal direction is more restricted. Besides, the shear strength tends to increase with increasing temperature, particularly if the fracture is heated under a large normal stress; at the greatest temperature, the shear strength is deteriorated. The strengthening of rock fracture upon heating is associated with the time- and temperature-dependent asperity contact creep which increases the real contact area of the macroscopically mated fracture surfaces. The sequence of heating and normal loading prominently affects the shear properties of granite fractures; the shear strength, post-peak stress drop and stick–slip amplitude are greater for granite fractures which were normal loaded first than heated first. The post-peak stress drop and stick–slip stress drop, which are vital parameters to estimate the seismic event intensity, are related to the corresponding dynamic slip and loading system stiffness. Highlights: Direct shear tests were conducted on granite fractures with a newly developed apparatus equipped with real-time heating capability. The thermal expansion is smaller while the AEs are more active when the fractures were heated under a larger normal stress. The shear strength of granite fractures first increases and then decreases with increasing temperature when heated under a large normal stress. The shear strength, post-peak stress drop and stick–slip are greater for granite fractures which were normal loaded first than heated first. The strengthening of fractures heated under a large pre-set normal stress is related to increase in fracture contact area due to asperities creep. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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