![Ministry of rock 2 crack](https://kumkoniak.com/56.jpg)
Geological disasters such as spalling and rock burst occur frequently, which seriously restrict the development of deep underground engineering in the world ( Martin et al., 1999 Feng, 2011 Li et al., 2017 Gong et al., 2019 Gao et al., 2021). With the increasing excavation depth of deep underground engineering in the world, the influence of high ground stress and complex geological environments on deep rock mass is increasing.
![ministry of rock 2 crack ministry of rock 2 crack](http://www.slicingupeyeballs.com/wp-content/uploads/2018/07/peter-murphy.jpg)
The research results of this study could supply a useful reference for the understanding of deep hard rock fracture behavior. Meanwhile, the expansion rates of three different racking types are calculated by simplified treatment, which are about the order of 10 −5–10 –4 m/s. It is found that there are three different types of cracking processes in granite.
![ministry of rock 2 crack ministry of rock 2 crack](http://www.renegadetribune.com/wp-content/uploads/2016/09/manson-and-co.jpg)
In the range of stress level in this study, when σ 3 is high, the fracture angle of granite increases with increasing σ 2, and its regularity is obvious, while when σ 3 is low, the regularity of the fracture angle increases with the increasing σ 2 is not obvious. The overall level of the rock fracture angle ( θ) at low σ 3 is higher than that at high σ 3. It is concluded that under a true triaxial condition, the number of post-peak steps increases first and then decreases with the increasing σ 2, which implies that the rock failure evolves from shear failure to a more complex tension–shear mixed failure and finally evolves into a failure mode dominated by tensile failure. Therefore, this study carried out relevant true triaxial compression tests and acoustic emission (AE) monitoring. However, there are relatively few research studies on the post-peak mechanical behavior and fracture characteristics of hard rock under true triaxial stress. The post-peak behavior and fracture characteristics of hard rock are correlated with the stability and bearing capacity of engineering rock mass.
- 5The Center of National Railway Intelligent Transportation System Engineering and Technology, China Academy of Railway Sciences Corporation Limited, Beijing, China.
- 4State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu, China.
- 3Fujian Key Laboratory of Geohazard Prevention, Fuzhou, China.
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2Key Laboratory of Geohazard Prevention of Hilly Mountains, Ministry of Natural Resources, Fuzhou, China.1School of Emergency Science, Xihua University, Chengdu, China.Feng Zeng 1,2,3*, Meiben Gao 1,2,3,4, Fujiang Chen 1,2,3, Yongyi Yang 1,5 and Yan Zhang 4*