## 3 Comparative Analysis of Working Performance of Pile-Raft System
### Results and Discussion  
#### 3.3.1 Performance of raft  
Figure 11 shows a comparative diagram of the settlement curves of the longitudinal central section of the raft of the four simulation schemes. The maximum settlement \(S_{\text{max}}\) of Scheme 2 was the largest (\(S_{\text{max2}}=-43.8\) mm), that of Scheme 1 was the smallest (\(S_{\text{max1}}=-30.43\) mm), and those of Schemes 3 and 4 were slightly larger than that of Scheme 1. It is evident from the settlement distribution in Figure 8 that \(S_{\text{max2}}\) of Scheme 2 appeared at the right end of the raft, and the settlement curves of the other three schemes were approximately symmetrically distributed (i.e., \(S_{\text{max}}\) appeared near the center of the raft). The settlement distributions of the raft in the four schemes were uniform. The differences between the maximum and minimum settlements of the raft under each scheme were within 2 mm of one another.  
In Scheme 1, the bored piles were rigidly connected to the raft, and the settlement of the raft was the smallest. However, the joint between the top of the pile and the raft produced a relatively large bending moment. Figure 12 shows a comparative histogram of the extrema of the bending moments of the raft plate of the four calculation schemes, in which the value of the hogging moment of the raft in Scheme 1 \(M_{\text{min1}}=-815.8\) kNm/m, and the extremum of the moment of the raft plate of Scheme 1 was much higher than those in the other three schemes.  
Figure 11: Settlement curve of the longitudinal central section of the raft under the four simulation schemes.  
Figure 12: Comparison of extrema of the bending moments of the raft under the four simulated schemes.  
In Scheme 2, there was a cushion between the bored pile and the raft. Compared with the composite foundation consolidated by CFG piles in Scheme 3, the spacing of the bored pile in Scheme 2 was large, and a greater load was shared by the soil among the piles, which produced a greater compression deformation in Scheme 2. Moreover, because the stiffness of the bored pile was higher than those of the upper cushion and the underlying soil, a larger deformation was caused at the top and bottom of the pile under the action of the upper load, which had a certain effect on raft settlement. At the same time, the extremum of the bending moment of the raft was greatly reduced, i.e., the \(M_{\text{min}2}\) of Scheme 2 was 78.3% lower than the \(M_{\text{min}1}\) of Scheme 1.  
CFG piles were used in Scheme 3, where the settlement of the raft was close to that of Scheme 3. This shows that using piles with relatively low strength and setting a cushion layer with the appropriate thickness can give more play to the bearing capacity of the soil between the piles to control the settlement of the buildings well. At the same time, the bending moment of the raft foundation was clearly lower than that of the rigid connection of the pile-raft foundation. The pile-raft foundation with the relative moment of the raft plate was significantly smaller than M\({}_{\text{min}1}\), by 74.5%, i.e., \(M_{\text{min}3}\) of Scheme 3 was 74.5% lower than \(M_{\text{min}1}\) of Scheme 1.  
The reinforcement zone of the CFG pile in Scheme 4 was treated using the integral equivalent method. The difference between the maximum settlement of Scheme 4 and that of Scheme 3 was approximately 3.8%. The differences between the positive and negative bending moments of Schemes 4 and 3 were 10.9% and 7.5%, respectively. This indicates that the settlement and internal force obtained using the integral equivalent treatment method were similar to those obtained using the embedded pile simulation.