# Development of Rockburst Research: A Comprehensive Review
## 2 Rockburst Definition and Types
### Rockburst Types  
Both statistics of on-site rockburst data and physical model tests of rockburst are carried out based on rockburst type. Therefore, reasonable classification of rockburst type is of great significance. Table 2 presents the main rockburst types of classification schemes. [PERSON] divided rockburst into strain type and fracture type according to the slip of fracture surface and the degree of rock fracture [19]. [PERSON] et al. divided rockburst into three types: bulking, ejection and seismically induced fall of ground via a rockburst damage mechanism (See Figure 3a). [PERSON] et al. divided rockburst into three types: (a) instant rockburst, (b) standard rockburst and (c) delayed rockburst, according to the length of time from unloading to rockburst occurrence, along with two other types: (a) strainburst and (b) impact-induced rockburst. \begin{table}
\begin{tabular}{c c} \hline \hline
**Researchers (Year)** & \multicolumn{2}{c}{**Rockburst Definition and Its Description**} \\ \hline [PERSON] (2009) [12] & \(\bullet\) & Rockburst is a sudden and violent failure of rock mass, caused by highly stressed brittle rocks and the rapid release of accumulated strain energy. \\ \multicolumn{2}{c}{} \\ \multirow{2}{*}{[PERSON] (2014) [13]} & \(\bullet\) & Deep rock is under in situ stress and maintains in elastic range and the stored elastic energy is high enough to break the rock. If triggered by a certain degree of perturbation, the stored elastic energy is likely to release and break the rock mass and energy required to break the rock mass is greater than that carried by the perturbation, then we say rockburst occurs. \\ \multicolumn{2}{c}{} \\ \multirow{2}{*}{[PERSON] et al. (2017) [14]} & \(\bullet\) & The local stress concentration is caused by deep engineering excavation and the storage of large elastic strain energy in surrounding rock mass; thus, brittle rock failure may occur under the action of the external dynamic disturbance loading, causing the release of internal storage energy of the rock mass. Most of the released storage energy results in the destruction of the rock and the extra part of the energy results in the broken rock blocks ejected, which induces rockburst. \\ \multicolumn{2}{c}{} \\ \multirow{2}{*}{[PERSON] et al. (2018) [15]} & \(\bullet\) & Rockburst is a sudden and violent movement and collapse of rock in underground caves which occurs under high stress conditions. \\ \multicolumn{2}{c}{} \\ \multirow{2}{*}{[PERSON] et al. (2019) [16]} & \(\bullet\) & Rockburst is a dynamic phenomenon when the elastic deformation potential energy accumulated in underground engineering rock mass suddenly releases under excavation or another external disturbance, leading to the burst and ejection of surrounding rock. \\ \multicolumn{2}{c}{} \\ \multirow{2}{*}{[PERSON] et al. (2020) [17]} & \(\bullet\) & Rockburst is defined as damage to an excavation that occurs in a sudden or violent manner. \\ \multicolumn{2}{c}{} \\ \multirow{2}{*}{[PERSON] (2021) [18]} & \(\bullet\) & Rockburst is defined as a phenomenon with immediate dynamic instability under excavation unloading conditions of deep or high geostress areas. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._Based on in situ monitoring of rockburst in the Jinping II hydropower station, [PERSON] et al. divided rockburst into two types: (a) immediate rockburst and (b) time-delayed rockburst, according to occurrence time of rockburst. Immediate rockburst generally occurs during or after an excavation unloading effect, from a few hours to 1 to 3 days. Time-delayed rockburst generally occurs outside the excavation stress disturbance range of the tunnel face, 80% of which occurs 6-30 days after excavation in this area [24,25]. [PERSON] et al. divided rockburst into six basic geomechanical types with unique development characteristics based on geomechanical analyses of a rockburst event which occurred in China (See Figure 3b) [28].