# Development of Rockburst Research: A Comprehensive Review
## 4 Rockburst Mechanism  
Although the main factors affecting the occurrence and severity of rockburst have been roughly clear, it is obviously difficult to reveal and unify the mechanisms of rockburst under different geological environments and excavation disturbances. Researchers try to explain formation conditions and development processes of rockburst from different angles by studying different engineering examples and physical model tests. [PERSON] and [PERSON] summarized the main factors influencing rockburst damage and its severity (See Figure 5) [30]. Figure 4: In situ monitoring for rockburst: (**a**) seismic motion wave frequency spectrum and field of application of AE/MS techniques (from [67]), (**b**) structure of a microseismic monitoring system in a mine (modified from [69]), (**c**) pattern recognition for microseismic signals (from [70]). [PERSON] et al. used a digital borehole camera, cross hole acoustic meter and sliding micrometer to monitor the tunnel excavation process of the Jinping II hydropower station and then summarized the rockburst precursory characteristics and four stages of rockburst development [81]. [PERSON] et al. used the general particle dynamics (GPD) program and Holmquist-Johnson-Cook damage model (HJC) to simulate rockburst phenomena caused by fracture evolution, which revealed the two-dimensional and three-dimensional crack propagation processes in the surrounding rock [82]. [PERSON] et al. used scanning electron microscopy (SEM) to analyze the failure/fracture propagation mode of rockburst fragments and proposed that it was helpful to reveal the true source mechanism of microseismic events (if its original source is known) [83]. [PERSON] et al. studied the influencing factors of slip rockburst caused by a structural plane through physical model tests. The results showed that the normal stress level had a great impact on the failure mode of joints, which is consistent with the analysis results of in situ microseismic monitoring [57; 84]. [PERSON] et al. put forward a new theory of static-dynamic coupling and developed the corresponding true triaxial test device. The results showed that internal pre-static stress was the dominant factor of rock failure and external dynamic disturbance stress was an important inducement [85]. [PERSON] et al. studied the causes of rockburst induced by collapse via a true triaxial test system, which is mainly reflected in promoting large buckling deformation (providing energy for rockburst) and weakening rock strength (creating conditions for a sudden release of energy) [86]. [PERSON] et al. regarded rockburst as a buckling (instability) phenomenon of a structure. By establishing a rigorous mathematical model, the parametric resonance in induced and triggered rockburst was revealed, the quantitative relationship between blasting parameters and rockburst was established and the critical static load conditions of an inherent rockburst were obtained [29]. In situ microseismic monitoring shows that most of the monitored rockbursts have microseismic precursors [87]. When rockburst occurs, accumulated energy and the number of microseismic events reach the maximum [88]. Using the energy rate, moment tensor analysis and the P-wave development method based on actual microseismic information, supplemented by in situ macro failure characteristics of rockburst and identification of rock fracture modes (tension, mixing and shear), is a promising way to interpret rockburst mechanism [89]. [PERSON] et al. revealed the time characteristics of rockburst through microseismic monitoring results of a time-delayed rockburst and uniaxial dead load test. The time behavior of rockburst is the time behavior of crack propagation under high stress. When the internal damage of rock mass accumulates to a critical stage, even if there is no obvious excavation disturbance, rock mass may still be unstable [90]. Based on the thin plate theory, [PERSON] et al.