# Study on Dynamic Loading Characteristics of Rock Containing Holes
## 6 Conclusions  
Based on the experimental and numerical model, this study explored the impact of strain rate on the dynamic mechanical characteristics of specimens with holes. Continuous monitoring of the stress field surrounding the holes and a comparative analysis of degradation modes facilitated a comprehensive examination of the variations in stress field distribution and failure mechanisms between specimens with a single hole and those with double holes. The following conclusions can be drawn from this study:  
1. All specimens demonstrated a distinct strain rate dependency, yet the sensitivity of the dynamic mechanical properties of double-hole specimens to strain rate diminished with increasing hole radius. As the strain rate escalated, the growth in dynamic mechanical strength and peak strain for double-hole specimens with larger diameters became less pronounced.
2. Upon analyzing the stress field monitoring results for each specimen under varied strain rate loading conditions, a shared trait among all specimens was identified: the emergence of low-stress zones at the axial vertices of the holes, aligned parallel to the loading direction. A key distinction was observed in the stress distribution patterns: single-hole specimens exhibited stress concentration at the radial vertices of the holes, oriented perpendicular to the loading direction. In contrast, double-hole specimens demonstrated a more uniform stress distribution across various angles, lacking distinct stress concentration zones within the strain field.
3. Under varying strain rate loading conditions, the failure patterns observed in all single-hole specimens were consistent, and double-hole specimens exhibited comparable traits. Analysis of these failure modes through displacement fields revealed that shear cracks were the primary macrocracks, which segmented the specimens into multiple blocks. While initial crack formation in both specimen types began at the specimen ends, crack initiation and propagation in single-hole specimens predominantly occurred around the holes. Conversely, in double-hole specimens, some cracks developed around the rock bridge connecting the two holes.
4. The implementation of large-diameter borehole pressure relief measures has been shown to not only enhance the stress distribution surrounding the boreholes but also facilitate the formation of macrocracks by offering displacement space for the movement of end blocks, thereby diminishing the generation of microcracks during the failure process. Furthermore, this study revealed that under high strain rate conditions, the damage at the incident end of the rock specimen was predominantly characterized by shear cracks, which exhibited greater displacement. These insights have the potential to significantly refine borehole pressure relief strategies in deep tunnel applications.  
Conceptualization, C.Z.; Methodology, M.C.; Formal analysis, C.X.; Investigation, M.C. and X.W.; Resources, C.Z.; Data curation, X.W. and H.T.; Writing--original draft, Q.L.; Funding acquisition, C.Z. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the National Natural Science Foundation of China (52374128, 42207201).  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
The authors declare no conflict of interest.