# A Comprehensive Review of Mechanisms, Predictive Techniques, and Control Strategies of Rockburst
## 4 Rockburst Mechanisms  
### Rockburst Instability Mechanisms  
Rockburst mechanisms may be pretty sophisticated because of the complex physical and mechanical qualities of rock masses, the triggering effects of geomechanical circumstances, and construction factors. The rockburst mechanisms are yet unknown. As [PERSON] [115] pointed out, it is not easy to agree on a definition of rockburst. Many research centers worldwide have looked at successful solutions to rockburst difficulties. These advancements represented a breakthrough in rock mechanics research and are of significant importance. [PERSON] and [PERSON] [14] also said that this form of progressive failure mechanism is not well understood, posing a dilemma for rock mechanics researchers. Several ideas on the mechanisms of rockbursts have been offered to date, including the strength theory, the energy theory, the bursting liability theory, the rigidity theory, and the instability theory. [PERSON] initially offered the strength theory [116], on which [PERSON], [PERSON], and [PERSON] [117; 118; 119] proposed additional strength requirements for rockbursts. However, the strength theory is required rather than sufficient for rockbursts. It can show whether or not a rock mass has failed. It cannot, however, determine if the rock mass collapse is steady or unstable, i.e., whether rockburst will occur. [PERSON] suggested the energy theory for rockbursts based on years of rockburst research in South Africa [24]. It was stated that rockburst happens when the mechanical equilibrium condition of the surrounding rock mass system is disrupted and the energy released exceeds the energy absorbed. [PERSON] suggested the energy rate hypothesis (Equation (1)) in the 1970s [120]:  
\[\left(\frac{dE_{R}}{dt}\right)+\beta\left(\frac{dE_{E}}{dt}\right)>\frac{dE_{D }}{dt} \tag{1}\]  
where \(\alpha\) is the effective coefficient of surrounding rockmass energy release, \(\beta\) is the effective coefficient of energy release of the orebody, \(E_{R}\) is the energy held by surrounding rockmass, \(E_{E}\) is the energy stored by orebodies, and \(E_{D}\) is the energy spent at the junction of orebodies and surrounding rock masses. The energy theory, based on the law of conservation of energy, overcomes the limits of conventional theory and provides a solution to the subject of the rockburst energy source. The energy hypothesis has a flaw in that it is impossible to identify the scope of surrounding rock masses relevant to fractured rock masses caused by  
Figure 6: The principle schematic of GDEM numerical model (**left**) and the failure process of bending-bulging rockburst (**right**) [114]. rockburst, making it difficult to compute the energy involved in the rockburst event [121]. As illustrated in Figure 7, rockburst happens during the pre-peak period, whereas rockburst occurs during the post-peak stage. Furthermore, because energy is connected to the stress and strain fields of the surrounding rock masses, which are difficult to quantify, the energy theory can only give some qualitative information for rockburst occurrence and cannot be used in engineering procedures to anticipate rockbursts. The [PERSON] hypothesis on bursting liability posits that rockburst occurs when the inherent bursting liability of a rock mass exceeds a critical value [123]. The bursting liability can be indicated by various measures, such as energy, duration, deformation, and stiffness indexes [66]. However, it is important to note that the burst liability index is just one aspect of the rock mass and the occurrence of rockbursts is influenced by both the rock mass characteristics and the stress conditions in the system. Therefore, the bursting liability index should be used as a reference for support design rather than as a criterion for rockburst occurrence. [PERSON] and [PERSON] were the first to obtain the complete stress-strain curve of marble using the rigidity theory by enhancing the test machine's stiffness.