## 5 Conclusions  
This paper takes the shield project of \"Keyuan Station \(\sim\) Shenzhen University Station\" section of Shenzhen Metro Line 13. Through the combination of theoretical analysis, numerical simulation and field test, the layered settlement characteristics of shield tunnel crossing composite strata are systematically analyzed. The following main conclusions are drawn:  
1. The weak reflectivity fiber grating sensing technology can better perceive the evolution law and distribution characteristics of vertical and horizontal settlement of composite strata caused by shield tunneling, which is in good agreement with the numerical simulation results, and has the advantages of automation and high precision, it can be used as a supplement and alternative method for traditional measurement methods.
2. The vertical and horizontal partition (layer) system of layered settlement of composite strata with the temporal and spatial evolution of shield tunneling is constructed. The temporal and spatial evolution law of ground settlement at different depths with shield tunneling can be divided into three stages in the longitudinal direction, namely, the shield approaching stage (\(-\)5D\(-\)0), the shield crossing stage (0\(-\)1D) and the shield tail detachment stage (1D\(-\)5D), and the 3D range after the shield crossing and the shield tail detachment is the longitudinal main disturbance area of layered settlement. Horizontally, the overlying composite strata are divided into main disturbance layer and secondary disturbance layer according to the influence of shield tunneling disturbance. Among them, the range of 0.5D stratum above the tunnel is the main disturbance layer.
3. According to the influence zone of the building (structure) and the different stages of shield construction, corresponding effective control measures can be taken to achieve accurate control of stratum displacement and safe and efficient tunneling of shield.  
Conceptualization, F.Z. and X.L.; methodology, F.Z. and X.L.; validation, F.Z. and H.S.; formal analysis, X.L. and B.L.; investigation, S.L.; resources, S.L. and K.D.; data curation, Y.F.; writing--original draft preparation, F.Z.; writing--review and editing, F.Z. and X.L.; funding acquisition, H.S. All authors have read and agreed to the published version of the manuscript.  
The authors would like to acknowledge the support provided by the 2019 China Construction Technology Research and Development Project Research on Key Technologies of Subway Construction under Multi-Factor Coupling (CSCEC-2019-Z-19).  
**Institutional Review Board Statement:** The participant's personal identification information used in the study did not include personal information. Ethical review and approval were not required for the study.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data sharing is not applicable.  
**Acknowledgments:** The authors would like to thank the anonymous reviewers for their valuable comments that helped improve the paper's quality. We also thank China Construction Communications Engineering Group Co., Ltd. for helping us collect research data.  
**Conflicts of Interest:** The authors declare no conflict of interest.