# Numerical Analysis of the Installation Process of Screw Piles Based on the FEM-SPH Coupling Method
## 4 Numerical Results
### Influence of Pile Structure Parameters on Soil Pressure  
As shown in Figure 18, it can be seen that there is consistency in the range of soil pressure variation during the installation of different screw piles. The obvious areas of soil pressure variations are mainly concentrated near the pile body, the helical blades and the conical pile body, indicating that it is these three parts that interact with the soil during the installation. For these micro screw piles with continuous blades, the installation force of the screw piles is mainly generated by the force between the soil and spiral blades. Therefore, as shown in Figure 18, most of the soil particles with higher pressure are located between the spiral blades. It can be seen that the shallow soil pressure is lower than that of the middle and deep soil at the end of the installation of the screw pile. Considering the soil failure mechanism of the screw pile during the installation process, it shows that the effect of HFM on the surrounding soil pressure around the screw pile is weaker than that of CSFM, and the variation in soil pressure is mainly caused by CSFM.  
Figure 17: Soil displacement contour caused by the installation of the screw pile: (**a**) NT2, (**b**) NT3, (**c**) NT4 and (**d**) NT5.  
For NT2 and NT3, as is shown in Figure 18a,b, the max soil pressure around NT3 is greater than that of NT2, which is 1.293 \(\times\) 10\({}^{6}\) Pa. It can be concluded that the maximum pressure of soil particles increases with the increase in pile diameter during the installation process. We can see from Figure 18a,b that the variation range of soil pressure is also related to pile diameter, which is positively correlated with pile diameter. For the two screw piles with different pile diameters, both the soil pressure values and the range of soil pressure variation around the pile are also different. This shows that when the pile diameter is varied, the two soil failure mechanisms caused by the installation of the screw pile will change the range of soil pressure around the pile and soil pressure values. This is mainly because, with the increase in the pile diameter, a larger contact area is created between the screw pile and the soil, resulting in a stronger squeezing effect and a higher pressure on the soil around the pile.  
For NT4 and NT5 (Figure 18c,d), the soil around the NT5 exhibited a greater pressure at the end of installation, which is 1.113 \(\times\) 10\({}^{6}\) Pa. The two screw piles have different spiral pitch, indicating the maximum soil pressure around pile increases with the increase in pitch during the installation process. It can be seen from Figure 18c,d that with the decrease in the pitch, the range of soil pressure around the pile does not vary, but the maximum value of soil pressure becomes smaller. From the above analysis, it can be seen that when the pitch is varied, the two soil failure mechanisms caused by the installation of the screw pile do not change the range of soil pressures around the pile, but the soil pressure values will be changed. This is because the closed-arranged blades will have a stronger shearing action with the soil particles around the pile, and the surrounding soil will be broken up. Therefore, the interlocking forces between the soil particles will become smaller, resulting in a greater range of pressure variations and a smaller pressure on the soil around the pile.