## 3 Test Results and Discussion
### Displacement of Soil around Pile under Failure Load  
In Figures 10 and 11, under the failure load (when the load reaches the vertical limit capacity), the displacement field of the soil around the pile expands compared to the working load (when the load is below the vertical limit capacity), and the direction of some soil particle displacements changes. The influence of the variable section and inclination on the soil remains consistent with that under the working load. When the pile loses its bearing capacity and the surrounding soil undergoes general shear failure, soil deformation extends from local to global. [PERSON] found that, under load, the vertical displacement of the soil around the pile compacts, forming a wedge-shaped region [32]. In Figure 12, the variable section does not enhance the bearing capacity of inclined piles. When the inclination is fixed, decreasing the variable cross-section diameter significantly reduces the influence range on the surrounding soil at the cross-section and pile end. As the diameter decreases, the soil deformation around the pile accelerates from local to global, and the pile's bearing capacity gradually decreases. During failure loading, the displacement direction of the soil around the pile changes. The soil at the pile end and variable cross-section shows similar behavior, with the deformation expanding from local to global. This indicates general shear failure, and the pile loses its load-bearing capacity. When the pile body is slightly inclined, the soil on both sides of the pile body increases the friction force on it; the vertical bearing capacity of inclined piles with a 2% and 4% inclination is greater than that of vertical piles with a higher-than-8% inclination. 2. For variable-section piles, the slope of the load-settlement curve becomes larger when the radial size of the variable section is too small (the ratio of the variable section to the diameter is 20/13), and, under the same load level, the corresponding settlement of variable-section monopiles with a small radial size of the variable section is larger, and, for the diameter of the variable section of 17 mm and 15 mm, its corresponding settlement is smaller than that of the variable-section straight piles. 3. The change in the variation of the variation ratio at the variable section has a greater effect on the two-dimensional deformation of the soil around the pile than the inclination. The presence of a variable section does not improve the bearing capacity of variable-section inclined piles at inclination angles that are too large. But there are many problems that need to be improved urgently: From the consideration of the test site conditions and materials, the nature of the soil of transparent soil is a single saturated sandy soil, while the geological conditions in the actual geotechnical engineering are more complicated. Compared with the objects measured in the traditional pile foundation test, no relevant measurements were made for the soil displacement at the pile end, bending moment of the pile body, and soil stress at each place of the pile perimeter and pile end, and the changes in the above parameters under different vertical loads could not be monitored and quantitatively analyzed. The follow-up study can improve the status quo of the test study, which can be improved from the nature of the soil layer, soil type, and other soil materials used in the test. This work is the result of collaboration among all authors. Q.M. : supervision, resources, funding acquisition, conceptualization, and writing--review and editing. J.L. : writing--review and editing, validation, software, methodology, investigation, and data curation. L.L. : writing--review and editing, supervision, and methodology. X.L. : conceptualization, supervision, validation, methodology, and formal analysis. All authors have read and agreed to the published version of the manuscript. This work was supported by the National Natural Science Foundation of China (No.