## 6 Conclusions  
Based on the Jinshui River flood control project in Zhengzhou City, the impact of groundwater fluctuations on the stability of super-large-diameter caisson structures under normal conditions, loose soil, void, and tilted structures were analyzed. The applicability and enhancement effects of permeable polymer, foam polymer, and anchor technologies in loose soil, voids, and tilted caisons were discussed. The following conclusions are drawn:  
1. Post construction, the caisson exhibits horizontal displacement towards the excavation pit, with a maximum displacement of approximately 8.0 mm occurring at a depth of one third to one half of the excavation pit, showing a trend of small at both ends and large in the middle. With the concrete bottom filling the excavation space and increasing the support force of the soil, the settlement and deformation of the soil are reduced.  
Figure 19: Comparison of horizontal displacement of the caisson structures with different anchor lengths.  
Figure 18: Comparison of mechanical behavior of caisson structures with different anchor cross-sections.  
Seasonal groundwater fluctuations with relatively small amplitudes do not induce significant displacements and stresses changes in the caisson structure. The maximum displacement and stress in the caisson caused by groundwater fluctuations are measured at 0.14 mm and 0.017 MPa, respectively.
* With the increase in soil looseness, the maximum deformation of the caisson reaches 2.05 mm. The reduction in tensile stress is most significant when the soil's elastic modulus decreases from 15 MPa to 5 MPa. The use of permeable polymer grouting can significantly enhance the soil's compaction and bearing capacity, thereby strengthening the structural stability of the caisson.
* Soil voids markedly alter stress distribution within soil layers. A void length of 4.0 m leads to a 41% greater caisson deformation compared to a void length of 2.0 m. Voids near the jacking pipes induce a maximum displacement that is 2.4 times greater than the displacement induced by those located in the middle of the caisson. Larger void sizes and lower void positions adversely impact caisson structural stability. The use of foam polymer materials effectively mitigates these adverse effects.
* Tilted loads induce significant deformation in the caisson. With a tilted load of 0.15 MPa, the maximum horizontal displacement of the caisson is 6.8 times larger than that without a tilted load. Anchoring mitigates damage from inclined loads, with effectiveness improving with larger cross-sectional areas and longer anchor rod lengths.  
Conceptualization, B.L.; methodology, L.D. and Y.Y.; investigation, data curation and supervision, H.W.; project administration, D.D. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Postdoctoral Science Foundation of China (No. 2022 TQ0305) and the Youth Talent Promotion Project of Henan Province (No. 2023 HYTP016), for which the authors are grateful.  
Not applicable.  
The data presented in this study are available in the article.  
Author [PERSON] was employed by the company Zhengzhou Zhengfa Water Conservancy Engineering Company Limited. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.