# Numerical Simulation Analysis Method for Rockburst Control in Deeply Buried Caverns
## 2 Mechanism and Control Measures of Rockburst
### Rockburst Mechanism and Evaluation Methods  
From numerous examples of rockburst in engineering practice [23], it is evident that as the excavation depth of underground engineering increases, the stress concentration in the surrounding rock also increases. Consequently, the frequency and severity of rockburst gradually escalate. It has been shown that rockburst is closely related to factors such as initial geostress, rock mass characteristics, stress concentration, and energy release. Currently, there are various methods of judging and grading rockburst [24]. These methods are primarily based on two criteria: the strength theory, which focuses on stress concentration leading to failure during excavation, and the energy theory, which emphasizes the sudden release of energy. The strength theory analyzes the occurrence of rockburst based on the strength condition and the degree of stress concentration in rock masses. [PERSON] [25] summarized several rockburst examples and proposed that the grade of rockburst can be evaluated by considering the rock's uniaxial compressive strength and stress ratio. Appendix Q of the 2008 edition of the Code for Geological Investigation of Hydraulic and Hydropower Engineering (GB50487-2008) [26] in China classifies rockburst into four categories: light, medium, strong, and extremely strong. This classification is based on the ratio of the uniaxial compressive strength of the rock to the initial stress of the surrounding rocks. During the excavation process of underground caverns, various factors can influence the rock mass, including the storage environment, characteristics of the rock mass, cavern structure, and excavation method. The stress in the surrounding rock is constantly being adjusted. On the one hand, the stress in the surrounding rock will be concentrated. On the other hand, the cracking of the surrounding rock will result in ongoing damage to the strength of the rock mass and a reduction in the bearing capacity of the surrounding rock. When the strength-to-stress ratio of the rock mass is too low, a rockburst will occur. Therefore, in the analysis of excavated underground caverns, in order to facilitate numerical analysis and calculations, the rockburst grade can be determined based on the ratio of rock mass strength damage to stress concentration. \[S=\frac{DR_{b}}{\sigma_{sm}} \begin{cases}4\ \sim 7&\text{Grade I light rockburst}\\ 2\ \sim 4&\text{Grade II medium rockburst}\\ 1\ \sim 2&\text{Grade III strong rockburst}\\ <1&\text{Grade IV extremely strong rockburst}\end{cases}  \tag{1}\]  
where \(R_{b}\) is the uniaxial compressive strength of the rock mass, \(\sigma_{sm}\) is the maximum concentrated stress value of the rock mass element during the excavation process, and \(D\) is the damage coefficient of the rock mass during the excavation process. The damage of rock mass materials increases with the accumulation of plastic deformation. When the rock mass structure reaches peak strength, the damage to the rock mass degree increases quickly. Therefore, the damage to the rock mass can be described by the exponential function [27]  
\[D=1-\exp\left(-A\sqrt{\varepsilon_{i}^{p}\cdot\varepsilon_{i}^{p}}\right) \tag{2}\]  
where \(\varepsilon_{i}^{p}\) is the accumulated plastic strain of stage \(i\) of excavation and \(A\) is a parameter related to rock mass damage. The energy theory analyzes the occurrence of rockburst from the perspective of energy release. [PERSON] et al. [28] studied the phenomenon of rockburst in gold mines in South Africa and concluded that when the energy released by the surrounding rock after excavation is greater than the energy consumed by the cracking of the rock mass, rockburst will occur. According to the energy rate theory, [PERSON] et al.