## 6 Conclusions  
This paper analyzes different structural forms with different influencing factors against the background of actual engineering and applies longitudinal and transverse tie beam forms to treat the landslide section. The landslide accident at the PHC pipe pile composite roadbed in the K31+140-K31+312 section was attributed to the insufficient bearing capacity of the roadbed structure, with causes related to construction, design, management, and on-site monitoring. The accident could be primarily attributed to the original treatment scheme's low horizontal bearing capacity and poor resistance to interference. By combining engineering monitoring data and finite element analysis, this study verifies the feasibility of finite element analysis and the bearing capacity of the overall structural form of the PHC pipe pile composite roadbed with longitudinal and transverse tie beams. The main findings are as follows:  
1. The order of the FOS of different structural forms is as follows: longitudinal and transverse tie beams > transverse tie beams > longitudinal tie beams > PHC pile with pile caps > monopile structure. Compared with the structural form of a PHC pile with pile caps, the FOS of transverse tie beam structures and longitudinal tie beam structures increased by 42.47% and 38.61%, respectively, while that of longitudinal and transverse tie beam structures increased by 50.87%. 2. In the case of a constant pile/soil load ratio, the FOS of the composite roadbed increases as the pile length increases (or pile spacing decreases), resulting in a decrease in roadbed settlement. When the pile/soil load ratio is 5.5, the change in pile length has s minimal influence on the FOS of the roadbed. For pile/soil load ratios of 6:4 or higher, the FOS of the roadbed with a pile length of 20 or more is greater than 1.4, and the increase in pile length has a smaller effect on the settlement of the composite roadbed. Under pile/soil load ratios of 6:4, 7:3, and 8:2, the FOS remains greater than 1.4 for pile spacings up to 3.0 m.
3. As the pile verticality increases from 1 to 8\({}^{\circ}\), the settlement of the composite roadbed gradually increases, while the contribution of the deep soil layer to the roadbed's bearing capacity gradually decreases. It should be noted that with half-width loading, a fast loading rate and an excessively high single filling height can reduce the stability of the composite roadbed. For optimal stability, a single filling height around 0.6 to 0.9 m is recommended. 4. The slip road section adopts the overall structural form of a PHC pipe pile composite roadbed with longitudinal and transverse tie beams, and the settings of piles and bedding layer are optimized. The monitoring results demonstrate that this form  
Figure 13: (**a**) Settlement time course comparison curves and (**b**) settlement contour plots for finite elements. effectively reduces the post-work settlement and horizontal displacement of the composite roadbed, improves the overall stability of the roadbed, and exhibits a strong resistance to disturbances during construction. It achieves vertical settlement control and horizontal slip resistance. 5. In order to effectively address various engineering conditions, it is important to select the appropriate bearing structure form for composite roadbeds. During the design process, it is crucial to consider the impact of each construction factor. The practical experience gained from previous engineering projects can serve as a valuable reference for future applications and management. Conceptualization, B.H. and Y.Y. ; methodology, X.L. ; software, Y.Y. ; validation, D.S., Z.S. and G.W. ; formal analysis, Y.Y. ; investigation, Y.Y. ; resources, B.H. ; data curation, X.L. ; writing--original draft preparation, Y.Y. ; writing--review and editing, G.W. ; visualization, Z.S. ; supervision, D.S. ; project administration, B.H. ; funding acquisition, X.L. All authors have read and agreed to the published version of the manuscript.