# Enlarged Head Pressure-Dispersed Anchor Cable for Foundation Pit Engineering Purposes
## 4 Numerical Simulation Analysis of the Anchor-Cable Support System
### Results and Analysis of the Numerical Simulation
#### 4.2.1 Support Effect of the Enlarged Head Pressure-Dispersed Anchor Cable on Foundation Pit
The horizontal displacement contour diagram of each position in the foundation pit after the foundation pit excavation was completed is shown in Figure 21. It can be seen that the enlarged head pressure-dispersed anchor cable increased the integrity of the pile and the soil outside the foundation pit and played an obvious reinforcement role on the pit wall. The horizontal displacement of the support pile under different conditions is shown in Figure 22. Working Condition 3 completed the construction of the support pile, where the horizontal displacement of the pile was 0. Working Condition 7 indicates that the seepage forces during precipitation increased the horizontal displacement of the support pile to some extent. Before Working Condition 10, the precipitation of confined water was basically completed, the water content of soil outside the foundation pit was reduced, and the change of seepage path caused the horizontal displacement of the support pile to be reduced slightly. Working Conditions 6 and 9 indicate that the anchor cable obviously controlled the horizontal displacement of the support, and the maximum reduction displacement of the pile top was about 2.5 mm. The horizontal displacement of the pile body was the largest at the top of the pile. The greater the displacement of the pile body is, the greater the axial force of the anchor cable is [27]. Figure 21: Final horizontal displacement cloud image. Figure 17:0 Surface settlement curve around the foundation pit under different working conditions. 2.2 Comparison of Support Effects of Enlarged Head Pressure-Dispersed Anchor Cables and Enlarged Head Tension Anchor Cables  
The enlarged head pressure-dispersed type and the tension-type anchor cable were simulated, respectively. Under the same circumstances, only the stress mode of the anchor cable was changed. The enlarged head tension-type anchor cable effectively bonded with concrete by a steel strand, while the enlarged head pressure-dispersed type anchor cable was still rigidly connected with the embedded plate by a non-sticky connection steel strand. The axial force changes of the two types of anchor cable are shown in Figure 17:1  
During the simulation, the inclination angle of the anchor cable was set at 20 degrees, and the elevation of the anchor head of the first row of anchor cables was 4.3 m. The free section was 0-8 m, the ordinary anchorage section was 8-11 m with 350 mm diameter, and the enlarged anchorage section was 11-17 m with 600 mm diameter. The second row of the anchor cable had an elevation of 7.3 m, an inclination angle of 20 degrees, a free section of 0-6 m, and an enlarged section of 600 mm diameters. Figure 17:2 Changes in the anchor cable axial force under different working conditions. Figure 17:3 Changes in the horizontal displacement of supporting piles under different working conditions. As residual mortar was unavoidable in the free section during the actual construction, the simulation in this study was consistent with the actual situation, and the soil in the free section was not excavated. Conditions 6 and 9, respectively, applied prestress to the first and second rows of the anchor cables. In Cases 7 and 10, the value of axial force only increased slightly, which indicates that the seepage exhibited a little influence on the axial force compared with foundation pit excavation. In Cases 8 and 11, while excavating the soil body further, it was found that the axial force of the expanded head pressure-dispersed anchor cable was significantly increased. The maximum axial force of the first and second rows of anchor cables was 127.3 kN and 180.5 kN, respectively, but it was slightly lower than that of the extended head tension-type anchor cables. Case 9 shows that the axial force of the first row of anchor cables was significantly reduced after the second row of anchor cables was constructed, which indicates that they both played an important role in the foundation pit support.