## 5 Conclusions  
Using By combining on-site monitoring and numerical simulation methods. Simulate disturbance under normal excavation conditions before excavation. Based on simulation results, safety control measures will be taken for on-site excavation by monitoring surface settlement, pipe stress, and soil pressure on site. The evaluation of the impact of small-radius stacked tunnels crossing elevated bridges has led to the following conclusions:  
1. Through disturbance simulation under normal excavation conditions, it was found that as the shield tunneling construction continued to advance, the cumulative settlement value of the bridge piers eventually exceeded the warning value by 1 mm. Security control measures must be taken.
2. The settlement variation law of bridges is closely related to the spatial position of bridges and tunnels. In the area close to the tunnel, there is a significant change in surface settlement during the shield tunneling construction phase, and the force fluctuations on the pipe segments are significant. At this stage, the proportion of changes in surface settlement on the mainland to total settlement is relatively high. In areas far from the tunnel, significant changes in settlement occur during the tunneling phase of shield tunneling construction. The settlement variation during this stage accounts for a relatively high proportion of the total settlement.
3. The monitoring results of shield tunneling through elevated bridges after implementing safety control measures show that the deformation of the bridge and surface settlement are significantly reduced. The stress situation of the pipe segments is within the allowable range and meets the safety control standards. Verified the effectiveness of security control measures.
4. During construction, the grouting method can adopt a sequential hole pattern, and it is best to use the grouting construction method of interval jumping holes, gradual constraint, and first from bottom to top. During grouting construction, 3-5 leveling observation points should be set up on the surface for monitoring, and cracks and uplift are not allowed to occur on the ground. Once cracks and uplift occur on the ground, the grouting pressure and amount must be adjusted in a timely manner.  
Conceptualization, T.Y. and X.P.; methodology, T.Y.; software, X.P.; validation, X.H. and B.L.; formal analysis, X.H., B.L. and T.W.; investigation, T.Y.; resources, X.P.; data curation, T.Y.; writing--original draft preparation, X.P.; writing--review and editing, T.Y.; project administration, K.L., J.Z. and Y.L. 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 (Grant Nos. 52074258 and U22A20234), Hubei Provincial Natural Science Foundation Outstanding Youth Project (Grant No. 2022 CFA084), Hubei Provincial Key Research and Development Program (Grant No. 2021 BCA133), Wuhan City Knowledge Innovation Special Project(Grant No. 2022010801010162), and Youth Innovation Promotion Association member program of Chinese Academy of Sciences.  
Not applicable.  
Informed Consent Statement: Informed consent forms have been obtained from all participants in the study.  
The data presented in this study are available on request from the corresponding author due to detailed data involves some privacy.  
The author [PERSON] is employed by the School of Urban Construction at Wuhan University of Science and Technology. The remaining authors declare that the study was conducted in the absence of any commercial or financial relationships that could be interpreted as potential conflicts of interest.