## 4 Parametric Studies
### Properties of Embankment Fill  
The cohesion and friction angle of the fill have a significant effect on the load transfer of piled embankments. Figure 15 shows the distribution of vertical stresses in the embankment with varying embankment heights under different conditions of fill cohesion and friction angle. As the cohesive strength and friction angle increase, the load transfer to the piles is gradually enhanced. However, the influence of cohesion is much less significant than the friction angle. With an increase in the friction angle from 20\({}^{\circ}\) to 40\({}^{\circ}\), the vertical stress on the piles increases by 32.2%, while the vertical stress above the subsoil decreases by 34.9%. On the other hand, with an increase in cohesion from 1 kPa to 7 kPa, the vertical stress on the piles only increases by 12.7%, and the load above the subsoil decreases by only 18.2%. Moreover, it has been found that with an increase in the friction angle, there is a slight decrease in the soil arch height. However, with an increase in cohesion, the soil arch height remains relatively unchanged.  
Figure 14: Variation in K with normalized embankment heights.  
Figure 16a presents the distribution patterns of the earth pressure coefficient in the embankment for different amounts of fill cohesion and friction angles. It has been found that the \(K\) in the embankment continuously increases as the cohesion increases. Especially at \(c=7\) kPa, the \(K\) value reaches 2.42, indicating a seemingly more mature soil arching effect. However, it should be noted that the calculation of the \(K_{\text{p}}\) in Rankine theory does not consider soil cohesion. It is only applicable to soils with low cohesion. The calculated value of \(K_{\text{p}}\) is underestimated when the fill cohesion reaches 7 kPa. Therefore, it is impossible to conclude whether the soil arching strengthens with increased cohesion.  
Figure 15: Variation in vertical stress with different properties of embankment fill: (**a**) cohesion; (**b**) friction angle.  
Figure 16b illustrates the variation in \(K\) values in the embankment with different fill friction angles, along with the corresponding \(K_{0}\) and \(K_{\rm P}\) values. It has been found that the \(K\) value in the embankment continues to increase as the friction angle of the fill material increases, indicating a stronger arching effect, but the peak value of \(K\) remains below \(K_{\rm P}\), and the soil arching is not fully developed. Therefore, selecting fill materials with higher friction angles can enhance the soil arching effect in the embankment supported by rigid floating piles, but does not cause plastic failure to occur.  
As shown in Figure 17, increasing both the cohesion and friction angle of the fill material is beneficial for reducing the settlement of the embankment. Compared to the friction angle, increasing cohesion leads to higher efficiency in settlement control. When the cohesion increases from 1 kPa to 7 kPa, the surface settlement of the embankment decreases by 72%, and the settlement of the subsoil reduces by 58%. On the other hand, when the friction angle increases from 20\({}^{\circ}\) to 40\({}^{\circ}\), the surface settlement of the embankment decreases by 22.8%, and the settlement of the subsoil decreases by 19.8%. During this process, the settlement at the pile top remains unchanged, indicating that increasing the cohesion and  
Figure 16: Variation in \(K\) with different properties of embankment fill: (**a**) cohesion; (**b**) friction angle.  
friction angle reduces differential settlements between the pile and the surrounding subsoil. Furthermore, the increase in cohesion and friction angle does not cause significant changes in the equal settlement plane. For embankments supported by rigid floating piles, the rational selection of fill materials with higher cohesion and friction angle is advantageous in reducing differential and surface settlement.