# Enlarged Head Pressure-Dispersed Anchor Cable for Foundation Pit Engineering Purposes
## 2 Analysis of the Force Mechanism
### End Resistance of the Enlarged Head Pressure-Dispersed Anchor Cable  
Through numerical simulation, the stress mechanism of the anchor cable was further explored. The free section of the anchor cable was 8 m, and the anchorage section was 9 m. The ordinary anchorage section was 350 mm in diameter and 3 m in length, and the enlarged head anchorage section was 600 mm in diameter and 6 m in length. The embedded plate had a diameter of 340 mm and was located at y = 0 m, y = 12 m, y = 14.5 m, and y = 17 m, respectively. Model size was 5 m \(\times\) 5 m \(\times\) 18 m. The geometry of the model  
Figure 3: Strengthening effect model of the end resistance to side resistance. is shown in Figure 4, the enlarged head pressure-dispersed anchor cable sample diagram is shown in Figure 5, and the material parameters are shown in Table 1.  
During the experiment, the pulling force was equally divided into six anchor cables. At 50 kN intervals, the pull-out resistance increased from 300 kN to 900 kN. Figure 6 shows the relationship curves of tension, side resistance, and the end resistance and displacement. It can be seen from Figure 6 that the maximum end resistance of the anchor cable reached 26.27% of the total tension. The side resistance before point A was generated by the relative displacement trend of the static friction force and after point A was mainly supplied by the sliding friction force. Point A to Point B is the process in which the plastic penetration at the grout-soil interface to the end resistance begins to play a leading role. After Point B, as the displacement of the anchor cable continued to increase, the end resistance accounts for more than 25% of the pull-out force. The end resistance at the variable section of the anchor cable becomes more and more important. Compared with the curve after Point B, the curve from Point A to Point B has some changes, and the slope decreases. When it approaches Point B, the curve tends to be smooth. Therefore, the \"end-pressing inflection point\" was near Point B. The remarkable feature was that on the tension-displacement curve, after the inflection point, the slope decreases, and the curve tends to be smooth. At this time, the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Category** & \begin{tabular}{c} **Volume** \\ **Modulus/kPa** \\ \end{tabular} & \begin{tabular}{c} **Shear** \\ **Modulus/kPa** \\ \end{tabular} & \begin{tabular}{c} **Density/kg/m3** \\ \end{tabular} & \
\begin{tabular}{c} **Friction Angle/\({}^{c}\)** \\ \end{tabular} &
\begin{tabular}{c} **Cohesion/kPa** \\ \end{tabular} \\ \hline Soil mass & \(3.5\times 10^{4}\) & \(1.62\times 10^{4}\) & \(1.85\times 10^{3}\) & 20 & 25 \\ M15 & \(1.41\times 10^{7}\) & \(8.87\times 10^{6}\) & \(2.00\times 10^{3}\) & 38 & \(3.0\times 10^{3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Material parameters. Figure 4: Quarter grid model. Figure 5: The enlarged head pressure-dispersed anchor cable sample diagram. displacement value was 15 mm, the end pressure reached the displacement required for the function, and the anchor solid slipped significantly. Moreover, the front end formed a large plastic sphere space, which was not suitable for carrying. With the continuous increase of displacement at the variable section of the anchor cable, the soil at the front end of the anchor solid is further compacted, the plastic zone of the soil at the front end of the anchor cable is further expanded, and the soil enters a deeper level of plastic expansion and redistribution of internal forces.