## 2 Experiments  
### Experimental Material  
In laboratory experiments simulating rockburst events, granite is commonly chosen as the test material due to its unique physical and mechanical properties, which align well with experimental needs [14; 19]. Rockbursts are a type of brittle rock failure that occurs under high-stress conditions, often accompanied by a sudden release of energy. Granite's high compressive strength (typically between 100 MPa and 300 MPa) and its tendency to fracture suddenly under stress make it an ideal candidate for studying these phenomena. Additionally, its high elastic modulus allows it to store significant amounts of elastic potential energy, making it particularly prone to sudden, rockburst-like failures when subjected to extreme stress. Granite is also known for its dense and uniform structure, which helps reduce random variations in test results, ensuring more consistent and reliable outcomes. Furthermore, granite is widely available worldwide, making it easy to obtain high-quality samples for research. While the specific composition and properties of granite can vary between regions, its overall mechanical behavior is remarkably consistent, meaning the findings from experiments using granite have broad applicability to real-world scenarios.  
In this study, granite samples AG2 and AG3 were selected for the simulation experiment of a strain-mode rockburst, as shown in Figure 1. While maintaining sample representativeness and broad applicability, the number of experimental repetitions may be reduced based on the following considerations:  
1. Consistency of physical and mechanical properties. The granite specimens were obtained from a Liuyang City quarry (Hunan Province), renowned for its homogeneous, joint-free granite formations that minimize experimental variability. This consistent geological background ensured that similarities in mineral composition, density, and mechanical properties were exhibited by the samples, thus facilitating a more accurate reflection of the mechanical behavior of the rocks under similar loading conditions.
2. Typical rockburst characteristics. Granite samples AG2 and AG3 exhibited typical strain-mode rockburst phenomena during the experiments, consistent with descriptions in the literature [20; 21], indicating that they are capable of effectively representing the rockburst behavior of this type of rock.
3. Rigorous experimental design. The granite samples were cut and polished into standard rectangular specimens measuring 100 mm \(\times\) 100 mm \(\times\) 200 mm. These specimens were designed to simulate the stress characteristics of rock mass elements exposed in underground spaces. To ensure accurate results, the surfaces of the specimens were finished to a high standard, avoiding uneven loading that could lead to localized stress concentrations.
4. Basis for preliminary analysis. Although only two samples were used, the data obtained are capable of providing valuable preliminary information for subsequent studies. Through a detailed analysis of these two samples, the key mechanisms behind rockburst occurrences can be identified, and a theoretical foundation can be established for the expansion of the sample size and the conduction of larger-scale experiments in the future.