## 7 Conclusions  
This paper presents a case study of neighborhood tunnels with small clearance in Shenzhen, China, where the minimum thickness of interlaid rock is only 0.5 m. In this study, numerical simulation and theoretical analysis were carried out to analyze the cross-sectional structural characteristics of the neighborhood tunnels. We aimed to propose a safety excavation partition scheme for the following tunnel. The conclusions are as follows:  
1. The damage mechanism of the interlaid rock under the blasting load from adjacent tunnels was investigated using LS-DYNA R11.1 software. The results suggest that meeting high-vibration control requirements for the upper and lower step zoning in the following tunnel is challenging, making it difficult to achieve damage control for the ultra-small clearance section for interlaid rock of 0.5 m thickness.
2. The four-part excavation method with reserved vibration-cushioning layer was proposed for the following tunnel. By incorporating a cushioning layer near the interlaid rock, direct damage from adjacent tunnel blasts was minimized. Based on the method of equivalent circles and the Schwarz Alternating Method (SAM), a mathematical model was established. By analyzing variations in surrounding rock stress with different thicknesses of the cushioning layer, the optimal thickness for the cushioning layer was determined to be 3.0 m.
3. Based on the parameters of the cushioning layer, the safe excavation partition scheme for the following tunnel was delineated. When the thickness of the interlaid rock exceeds 3.5 m, the benching method is employed for excavation. When the thickness of the interlaid rock ranges from 0.5 m to 3.5 m, the four-part excavation method with reserved vibration-cushioning layer is utilized. As a result of this case study, suggestions were identified for the safe excavation of neighborhood tunnels with small clearance.  
Conceptualization, X.W. and M.G.; methodology, X.W. and H.W.; software, X.W.; validation, X.W. and H.W.; formal analysis, H.W.; investigation, X.W. and H.W.; resources, M.G.; data curation, X.W.; writing--original draft preparation, X.W.; writing--review and editing, M.G. and H.W.; visualization, X.W.; supervision, M.G.; project administration, M.G.; funding acquisition, M.G. and X.W. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China, grant number 51934001 and the China Postdoctoral Science Foundation, grant number 2022 TQ0025.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
\begin{table}
\begin{tabular}{c c c} \hline
**No.** & **Name of Tunnel** & **Thickness of Interlaid Rock** & **Vibration Control Criteria** \\
1 & New Kurutage tunnel [34] & 15 & 10.7 \\
2 & Wutong mountain tunnel [35] & 13.5 & 4.0 \\
3 & Maoding tunnel [36] & 12 & 3.0 \\
4 & Xiaoyang mountain tunnel [37] & 9.2 & 10 \\
5 & Damao mountain tunnel [3] & 5.9 & 15 \\
6 & Jiaojin mountain tunnel [38] & 5.0 & 10 \\
7 & Wulong tunnel [39] & 4.0 & 25 \\
8 & Zhaobao mountain tunnel [40] & 3.0 & 12 \\ \hline \end{tabular}  
* Vibration monitoring points set up in the AT to close the explosion side, the length from the source of the explosion is equal to the thickness of interlaid rock.  
\end{table}
Table 5: Blasting velocity control criteria for some typical neighborhood tunnels 1.  
**Acknowledgments:** This work was supported by Chongqing Zhonghuan Construction Co., Ltd. We wish to acknowledge [PERSON] and [PERSON] for their help in conducting the field experiments for this study. Also, we would like to acknowledge the editors and reviewers for their invaluable comments.  
**Conflicts of Interest:** The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.