# Study on the Bearing Characteristics of Composite Foundations with Permeable Concrete Piles
## 4 Results and Discussions
### Influence of the Parameters of Pile  
This section investigates the effects of various factors on the settlement and pile-soil stress ratio of composite foundations with permeable concrete piles. These factors include pile length, diameter, cushion thickness, cushion modulus, inter-pile soil modulus, and pile body modulus. Numerical simulations determine the changes in composite foundation settlement and pile-soil stress ratio under different loads for each influencing factor. The patterns of these changes are then analyzed. Permeable concrete piles, which possess good permeability and a specific load-bearing capacity, typically have lengths ranging from 5 to 20 m. In the analysis, pile lengths were set at 6 m, 8 m, 10 m, 12 m, and 14 m, with other parameters kept constant. The influence of pile length on the settlement of composite foundations with permeable concrete piles and the pile-soil stress ratio was examined. The simulation results are shown in Figures 14 and 15. Figure 14 shows the influence of load on the settlement of composite foundations with different pile lengths. The figure indicates significant differences in the settlement behavior  
Figure 14: Influence of loads on settlement under different pile lengths. Figure 15: Influence of loads on pile–soil stress ratio under different pile lengths. of composite foundations under different pile lengths. Under the same load conditions, the settlement of the composite foundation decreases gradually with increasing pile length. Further analysis of the settlement at 300 kPa shows that as the pile length increases from 6 m to 14 m, the settlement decreases from 36.98 mm to 7.04 mm, a reduction of 440.16%. This demonstrates that increasing pile length has a significant effect on reducing foundation settlement. However, when the pile length increases from 12 m to 14 m, the decrease in settlement is relatively small. This is due to the existence of an \"effective pile length\". Once the pile length reaches this effective length, further increases in pile length have a less noticeable effect on reducing the settlement. Figure 15 shows the influence of load on the pile-soil stress ratio for different pile lengths. The figure indicates that the pile-soil stress ratio increases with increasing pile length. However, the influence of load on the pile-soil stress ratio is inconsistent across different pile lengths. For piles with lengths of 6 m, 8 m, and 10 m, the pile-soil stress ratio initially increases and then decreases with increasing load. In contrast, the pile-soil stress ratio increases with increasing load for piles with lengths of 12 m and 14 m. This is because shorter piles are more likely to reach their ultimate load-bearing capacity when subjected to higher loads. In comparison, longer piles can continue to bear the load more effectively, thereby providing a more stable load-bearing capacity. The pile diameters were adjusted to 0.3 m, 0.35 m, 0.4 m, 0.45 m, and 0.5 m, corresponding to replacement rates of 2.25%, 3.06%, 4%, 5.06%, and 6.25%, respectively. Other parameters remained constant. The influence of the pile diameter on the settlement and pile-soil stress ratio of composite foundations with permeable concrete piles was analyzed. The simulation results are shown in Figures 16 and 17. Figure 16 shows the influence of load on the settlement of composite foundations with different pile diameters. The figure indicates that under the same load, the overall settlement decreases as the pile diameter increases. Further analysis of the settlement at a load of 300 kPa shows that as the pile diameter increases from 0.3 m to 0.5 m, the settlement decreases from 16.7 mm to 10.37 mm, a reduction of 37.90%. This demonstrates that increasing the pile diameter significantly reduces the settlement of the foundation and improves its stability. Figure 17 shows the influence of load on the pile-soil stress ratio for different pile diameters.