## 5 Analysis of Test Results  
### Macroscopic Analysis of Failure Patterns of the Test Section  
The failure of the on-site test was mainly reflected in the failure of the sprayed layer. The overall thickness of the sprayed layer was 6 cm, which was far less than the axial length of the test section of 4 m. The sprayed layer belonged to a thin shell structure, which would be in a very unfavorable stress state when the explosive load was too large. The arch crown and 1/2 arch waist positions were most prone to stress concentration, leading to shear failure, delamination failure, and spalling of the sprayed layer. Therefore, for the sprayed layer or lining structure constructed inside the cavern, if the surrounding rock (soil) medium experiences significant deformation, it poses a great threat to the safety of the internal structure of the cavern. Therefore, the bolt structure type adopted in the protection project must have sufficient support stiffness, energy absorption characteristics, and sufficient deformation to better meet the needs of rock reinforcement in the protection project. Figure 11: A schematic diagram of explosive loading. There were 2 m long pilot tunnel sections before and after the two test sections, and the unexcavated soil at the end provided good constraints for each test section, ensuring that each test section had equally effective boundary conditions and did not cause aggravated damage to the inlet of the test section. The overall damage effect of each test section is shown in Figure 12.  
As shown in Figure 12a, after the third condition (W = 10 kg) test, the conventional steel-bolt-reinforced test section suffered serious damage, with the sprayed layer in the range from the arch crown to 1/2 arch waist deforming significantly vertically downward. There was serious delamination and shear failure on both sides of the 1/2 arch waist position, with large areas of the sprayed layer peeling off, exposing the mesh reinforcement and showing serious deformation and bending. The maximum length of the damaged area was measured to be 3.2 m, and the maximum width was 50 cm. As shown in Figure 12b, the degree of damage to the RDEA-bolt-reinforced test section was far less than that of the conventional steel-bolt-reinforced test section, with only mild delamination failure and shear cracks appearing at the 1/2 arch waist position. The displacement of the cavern wall directly reflects the deformation of the test section, which is the most direct and obvious response to the mechanical state and changes in the two test sections. It is also the most sufficient and effective parameter for analyzing the  
Figure 12: Overall failure diagram of the test section. (a) Comparison diagram of the overall test of the conventional steel-bolt-reinforced test section before and after (left: before testing, right: after testing). (b) Comparison diagram of the overall test of the RDEA-bolt-reinforced test section before and after (left: before testing, right: after testing). overall stability of the cavern. Due to the maximum deformation of the cavern crown under the explosion of the top cluster charges, the displacement of the cavern crown can best reflect the dynamic response of the two test sections under the explosion load of the three conditions. Therefore, this article selected the data of the crown displacement measurement point and analyzed it. The comparison chart of the crown displacement of the two test sections is shown in Figure 13, and the statistical table of the peak and residual values of the crown displacement is given in Table 2.  
As shown in Figure 13, the waveforms of the crown displacement measurement points of each test section were similar. Under the explosive load, the crown displacement rapidly increased to its maximum value, then rebounded slightly, and gradually tended to a stable residual value. As the explosive load gradually increased, the peak displacement and residual value of the crown displacement increased gradually.