# Research on the Self-Drilling Anchor Pull-Out Test Model and the Stability of an Anchored Slope
## 3 Self-Drilling Anchor Bolt Anchorage Mechanism Simulation Study
### Analysis of Numerical Simulation Results  
#### 3.4.1 Displacement Result Analysis  
Based on the initial stress field analysis, the \"initial\" command was used to set the velocity and displacement of all nodes in the model to zero along the XYZ axes, and then the uplift test of the self-drilling anchor bolt was simulated. A constant velocity boundary of 1 \(\times\) 10\({}^{-6}\) m/step along the Y-axis was applied to the exposed end nodes using the \"initial\" command, simulating the uplift process until the displacement reaches 26.1 mm, at which point the anchorage system fails. In the simulation, the displacement at the exposed end is the product of the constant velocity and the calculation step number. Meanwhile, the variations in axial force and shear stress during the uplift process were observed. Using the Fish language, the uplift load of the modified pile element at the corresponding displacement values was output based on the displacement values corresponding to each experimental data point. Under the condition of keeping the model soil parameters unchanged, the original unmodified pile element was also used to simulate the self-drilling anchor bolt. The resulting curve is shown in Figure 14.  
By observing the three data curves in Figure 14, it is clear that the magenta curve for the unmodified pile element does not match the experimental curve at all, whereas the blue curve for the modified pile element shows a high degree of agreement with the experimental numerical curve. However, due to the ideal conditions under which the numerical model  
Figure 14: Ultimate uplift capacity–displacement curve.  
is established, the modified pile element shows a slight lag in the elastic phase. At the same displacement, the numerical values are slightly lower than the experimental values by 6-9 kN. Additionally, the modified pile element enters the plastic phase later than observed in the experiment. In the experiment, when the displacement reaches 8 mm and the ultimate uplift capacity is around 195 kN, the anchor bolt enters the plastic deformation phase. In contrast, the modified pile element enters the plastic phase at 9 mm and around 210 kN. Once in the plastic phase, due to the near-ideal simulation conditions, the simulation curve for the modified pile element deviates slightly from the experimental values, with the corrected value being about 1% to 6% higher than the experimental data. When the anchor bolt begins to enter the partial failure stage around 20 mm of displacement and continues until 26.1 mm, when the ultimate uplift capacity reaches 272 kN and the anchor bolt enters the complete failure state, the curve for the modified pile element closely overlaps with the experimental curve. Therefore, it can be concluded that the modified pile element provides a good representation of the actual behavior in the model.  
The displacement contour plot at the ultimate uplift capacity of the self-drilling anchor can be seen in Figure 15. From Figure 15, it is evident that during the uplift process, a significant collaborative deformation phenomenon occurs between the pile unit anchor and the surrounding soil. Specifically, as the depth along the anchor centerline increases, the displacement of the soil also gradually increases. Moreover, the soil around the pile unit anchor exhibits a conical increase trend, resulting in an overall inverted conical shape in the displacement contour plot. This shape closely resembles the actual failure mode.