Effect of high temperature on the brittleness index of granite: an experimental investigation

• Published in: Bulletin of engineering geology and the environment Vol. 81; no. 11
• Main Authors: Yin, Tubing, Ma, Jiexin, Wu, You, Zhuang, DengDeng, Yang, Zheng
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2022
• Subjects: Earth and Environmental Science; Earth Sciences; Foundations; Geoecology/Natural Processes; Geoengineering; Geotechnical Engineering & Applied Earth Sciences; Hydraulics; Nature Conservation; Original Paper; Linear energy accumulation; Rock burst proneness; Brittleness index; Residual elastic strain energy; High temperature effect
• ISSN: 1435-9529; 1435-9537
• DOI: 10.1007/s10064-022-02953-z

Brittle index evolution is an important property of rocks in the context of mining engineering, as it often determines how severe the practical consequences of rock burst will be. However, the lack of knowledge of temperature and press on the brittleness index of hard rocks limits the further development of deep earth engineering. When fire breaks out in a deep underground rock project, the physical properties of the rock will change significantly, and the tunnel and pillars may be destroyed. The cylinder specimens were prepared, and uniaxial compression (UC) and single-cyclic loading–unloading uniaxial compression (SCLUC) tests were conducted on the thermal treated granite samples. This paper presents a new brittleness index based on the elastic strain energy evolution. The test results demonstrated that an increase in temperature results in obvious brittleness characteristics decrease of granite and rock burst proneness decrease with the increase. Meanwhile, it is found that the elastic strain energy density increases linearly with the total input strain energy density in the pre-peak curves with different temperature, confirming that the linear accumulate energy has not been altered by temperature. According to this inherent property, the peak elastic strain energy of granites after different temperature can be calculated accurately. On this basic, the relationship between temperature and energy evolution of granite was discussed, revealing that high temperature cause the energy dissipation, which is essential for reducing the rock brittleness. This study provides some new insights into the rock brittleness evaluation in high depth and high temperature rock engineering.