## 6 Conclusions  
This article examines the effect of excavating a new transverse roadway for vehicle traffic in the Yonghe tunnel on the existing lining of the tunnel. A three-dimensional finite element analysis was conducted to determine the dynamic response of the existing tunnel lining to nearby blasting vibrations. Based on the results, a safe distance threshold between the excavation face and the existing tunnel was established under the current blasting parameters. The conclusions are as follows:  
(1) The blasting-load-induced maximal vibration velocity of the existing tunnel is located at the hance of that. Moreover, the vibration velocity along the axial direction of the horizontal adit has a dramatic contribution to the resultant vibration velocity of the existing tunnel. Thus, the monitored measurement of the vibration velocity at this region should be enhanced during the construction, and the influence of the blasting load applied on the excavation face of the horizontal adit on the existing tunnel can be evaluated using the horizontal-radial vibration velocity;  
(2) The law of the stress of the existing tunnel induced by the adjacent blasting load is consistent with that of the vibration velocity. Similarly, the stress responses mainly locate the tunnel hance towards the direction of the blasting load. When the distance from the excavation face of the horizontal adit to the existing tunnel is 10 m, the blasting-load-induced maximal vibration velocity and dynamic tensile stress of the tunnel are only  
Figure 14: Relationship between the maximum vibration velocity and the maximum principal stress of the existing tunnel.  
2.96 cm/s and 0.20 MPa, respectively, which are far less than that stipulated by the related technical code;  
(3) A negative power exponent relationship between the maximal vibration velocity and the clear distance from the excavation face to the existing tunnel is observed. According to this relationship, the induced vibration velocity will exceed the threshold stipulated by the standard, i.e., 8 cm/s, if the distance decreases to 5.9 m. Considering the uncertainties in the site, such as the parameters of the surrounding rock, blasting construction, and the tunnel, the controlling distance of the background project is proposed to be 10 m under the current construction scheme.  
Conceptualization, W.Z., G.L. and Y.L.; methodology, W.Z.; G.L., software, Z.Z.; validation, W.Z., Y.L. and C.X.; formal analysis, Y.L.; investigation, G.L.; resources, W.Z.; data curation, C.X.; writing--original draft preparation, G.L.; writing--review and editing, W.Z.; visualization, Z.Z.; supervision, W.Z.; project administration, W.Z.; funding acquisition, Y.L. All authors have read and agreed to the published version of the manuscript.  
The author gratefully acknowledges the financial support provided by the National Nature Science Foundation of China: 51978677; the Shenzhen Natural Science Foundation (Sustainable Development Project: KCXFZ20201221173207020); and the GuangDong Basic and Applied Basic Research Foundation: 2023A1515030258.  
Not applicable.  
Data Availability Statement: Data available on request from the corresponding authors.  
The author declared that he has no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.