# Simulation Study on the Installation of Helical Anchors in Sandy Soil Using SPH-FEM
## 3 Simulation Results and Discussion
### Disturbance to the Soil by Helical Anchor Installation  
During the installation of the helical anchor, due to its unique combined motion of rotation and sinking, the soil around the anchor is subjected to the combined action of shear and compression, which leads to plastic deformation. To further explore the specific impact of this complex process on the soil, we select the 0.08 m pitch helical anchor as the research object and present the stress, displacement, and equivalent plastic strain PEEQ nephogram generated by the soil under the \"pitch-matching\" installation mode, as shown in Figure 6.  
Figure 4: Comparison of simulated and theoretical values of installation torque and compressive installation force. (**a**) Comparison of installation torque. (**b**) Comparison of compressive installation force, [PERSON], 1991 [8].  
Figure 5: Comparison of the uplift capacity factor for different embedment depth ratios, [PERSON] et al., 1991 [14]; [PERSON] et al., 2019 [10].  
According to the stress distribution nephogram (Figure 6a), it can be found that during the installation process of the helical anchor foundation, the vertical load is transmitted to the soil through the anchor rod and anchor plate, forming a significant stress concentration area around the anchor. After the installation of the helical anchor foundation is completed, the stress within the soil is mainly distributed around the anchor plate and the end of the anchor rod, forming an asymmetric \"V\" shape. The boundary of the stress area is approximately \(3D\) away from the anchor plate vertically, with the maximum load occurring directly below the anchor rod, reaching up to 2.653 MPa. For the soil more than \(3D\) away from the anchor plate, the stress influence is minimal.  
Further analysis of the displacement nephogram (Figure 6b) reveals that the soil experiencing displacement during the installation process is mainly concentrated near the projected area of the anchor plate. In conjunction with the research results proposed by [PERSON] et al. (2015), the disturbed area can be determined to be a cylindrical volume with a diameter of about 1.54\(D\). Within the cylinder, the displacement of the upper soil is significantly greater than that of the lower soil, especially within the 0.20 m range of the drilling point where there is a noticeable bulging of the soil, with the maximum bulging height reaching 0.09 m.  
The equivalent plastic strain nephogram (Figure 6c) shows that after the installation of the helical anchor foundation, the soil within the disturbed zone has essentially entered the plastic stage, with the PEEQ values in the disturbed zone exceeding 50 (red areas in the figure). It is noteworthy that the plastic strain generated in the soil at the top of the disturbed zone is lower than that at the bottom. This may be attributed to the smaller overburden pressure on the top soil during the installation process, which results in a relatively lower load experienced during the screwing process.  
To more intuitively reveal the movement characteristics of the soil in the disturbed zone, the displacement vector diagram of the soil in the disturbed zone is provided, as shown in Figure 7. It can be observed that the soil at the top of the disturbed zone has the largest displacement, and the direction of displacement is nearly vertical. With increasing depth, the direction of displacement gradually changes to horizontal. This indicates that after the helical anchor is installed to a certain depth, the soil displacement effect gradually becomes apparent, causing the diameter of the disturbed zone to be larger than the diameter of the anchor plate.  
Figure 6: Disturbance from stress, displacement magnitude, and PEEQ in soil after helical anchor installation. (**a**) Stress nephogram (Pa). (**b**) Displacement magnitude nephogram (m). (**c**) PEEQ nephogram (-).