## 6 Conclusions  
In this study, the surface settlement and deformation of the retaining structure caused by the excavation of a foundation pit with the PARB support system is studied by the numerical simulation method and compared with the original PAB support system. This study analyzes the difference in support effect by the two support systems, and finally analyzes the influence of embedded depth, ribbed beam size and waist beam size on the support effect of PARB support system. The research results demonstrate the following:  
(1) The numerical simulation results are highly consistent with the field monitoring data, which verifies the validity and accuracy of the numerical simulation model. The surface settlement and the deformation of the retaining structure meet the construction control requirements, which proves the applicability of the PARB support system.  
(2) Compared with the original PAB support system, when the foundation pit with the PARB support system is excavated to the bottom of the foundation pit, the maximum surface settlement decreases by 33%, and the maximum lateral deformation of the retaining structure decreases by 42%. The vertical deformation of the pile top of the retaining structure is too small to be ignored, because the anchoring force provided by the anchoring section of the pile and the preload provided by the anchor cable can effectively resist the vertical deformation of the pile. Those results show that PARB support system has a stronger support effect.  
(3) The PARB support system is consistent with the PAB support system in the surface settlement and the deformation of the retaining structure during excavation, and the curve of surface settlement presents in the shape of a \"V\". The position of maximum settlement is about one-half of the excavation depth from the retaining structure. The lateral deformation of the retaining structure is a parabolic curve. The maximum lateral deformation position is about 0.9 times the excavation depth from the top of the retaining structure.  
(4) An increase in the pile embedded depth and ribbed beam size can effectively improve the support effect of the retaining structure, while the increase in waist beam size does not significantly improve the support effect. Therefore, if it is necessary to improve the support effect of the retaining structure, it is suggested to increase the pile embedded depth and the ribbed beam size.  
Q.Y.: Conceptualization, methodology, supervision, project administration. H.-L.F.: Methodology, software, data processing, writing, original draft. All authors have read and agreed to the published version of the manuscript.  
Figure 15: Different waist beam size. (**a**) Maximum surface settlement. (**b**) Maximum lateral deformation.  
**Funding:** This work was supported by Hunan Provincial Education Department Foundation under grant No. 21 C0677, Natural Science Foundation of Hunan province under grant No. 2022 JJ50281 and Research and development project fund number of Hunan Chemical Geological Engineering Survey Institute Co., Ltd.: RD09.  
**Acknowledgments:** The authors thank the Advanced Research Center, Central South University, for providing the experiment conditions. The authors also express special thanks to the editors and anonymous reviewers for their constructive comments.  
**Conflicts of Interest:** The authors declare no conflict of interest.