# Development of Rockburst Research: A Comprehensive Review
## 3 Technologies and Methods for Rockburst Research
### Physical Model Tests  
Since rockburst is sudden, dynamic and instantaneous, physical model tests of rockburst have special requirements for similar materials, similar theories, instruments and equipment (for loading, excavation, support, monitoring and measurement). Hence, there are not many physical model tests on rockburst. Similar materials are the basis of rockburst physical model tests, which are mainly composed of aggregate materials (sand, slag, barite, etc. ), cementitious materials (gypsum, cement, epoxy resin, etc.) and additives to improve performance (water reducer, retarder, rosin alcohol solution, etc.) [56; 57; 58]. Although it is impossible to achieve the same violent ejection as an in situ phenomenon with similar materials, there should be ejection phenomenon with a low initial velocity. Therefore, the strength of the rockburst of the similar materials should not be too low so that some of the energy can be accumulated. In addition to meeting similarity conditions of basic mechanical parameters, the most critical point should meet a brittle similarity relationship. According to current test phenomena, there is almost no difference from general static failure, only slag falling, spalling, block falling and no dynamic instability process of surrounding rock from energy accumulation to sudden burst ejection. Consequently, it is necessary to explore more suitable similar materials, study the similarity of hard structural surfaces between original rock and similar materials and prepare structural planes with different geometric forms and mechanical properties in the specimens. In terms of loading devices, to facilitate observation, a simple two-dimensional loading mode was adopted in most tests (plane strain or plane stress [59; 60; 61]), and loading capacity was also weak. However, rockburst mostly occurs in deep buried high-stress rock mass, so a loading device needs to have a strong loading capacity. Occurrence of rockburst is not only affected by lithology and stress state, but also induced by blasting disturbance. If loading devices can provide static load (original rock stress) and dynamic load with frequency and amplitude (simulating an explosion stress wave), the action mechanism of the stress wave on rockburst may be revealed. However, how to quantify \"dynamic similarity\" between an in situ explosion stress wave and a simulated stress wave is a theoretical problem to be solved. Model excavation is also an important link. There are four main schemes:  
* A cylinder core is preinserted into a test specimen and then pulled out after the test specimen dries to complete the tunnel specimen. The effect of tunnel formation is good, but it does not well simulate the process of tunnel excavation and the characteristics of stress redistribution. * A cylinder core consisting of several small sections (the mechanical properties, such as elastic modulus, should be as consistent with the test specimen as possible) is preinserted into a test specimen and then pushed out in sequence (simulating sectional excavation) after the test specimen dries and is loaded to initial stress. The difficulty is that it is necessary to make the deformation of small sections consistent with the test specimen and small sections are difficult to be pushed out under high stress. * After the test specimen dries and is loaded to the initial stress, the specimen is manually excavated to create a tunnel by a drilling rig or small excavation machine. However, when the tunnel is long and there is concealed excavation, it is difficult to excavate manually in a narrow space. * The advantage is high efficiency, but there is still a great difference between a simple mechanical rock breaking mechanism and an in situ machine, which makes the accuracy of the test result low.