# Responses of Laterally Loaded Single Piles Subjected to Various Loading Rates in a Poroelastic Soil
## 5 Discussion and Conclusions  
The groundwater table plays a critical role in soil-structure interaction problems; however, most of the studies on laterally loaded single piles were seldom performed using the coupled hydromechanical governing equations or considering the soil as a porous media. The influence of the interaction of the porous soil media and the fluid flux during the loading stages of single piles was studied here using a coupled hydromechanical model for porous media.  
A series of analyses, conducted under different loading conditions: undrained (fast loading rate), partially-drained (slow loading rate), and drained (almost stationary loading rate) conditions, was performed in this study. The deflection of the laterally loaded single piles resulted in the tendency of the soil to expand and compress, and hence caused the generation of the excess negative and positive pore-water pressures on both sides of the laterally loaded pile. It was observed that the loading rates of the pile resulted in different degree of excess pore-water pressure generation and that the generation of the excess pore-water pressure has a significant effect on the response of the laterally loaded single piles. Under the fast or undrained loading condition, the negative excess pore-water pressure generated on the active side of the laterally loaded pile yielded a greater value than the positive excess pore-water pressure on the passive side. As the loading rate decreases, the negative pore-water pressure on the active side drops to values less than that in the passive side. It was also found in this study that most of the generation of the excess pore-water pressure occurred within the top 6.0 m of the pile, albeit excess pore-water pressure was also observed after this depth, but its effect on the pile responses was insignificant.  
Figure 6: Effect of pile length on lateral displacement of pile cap: (**a**) undrained (loading rate = 2 kN/s); (**b**) partially drained (loading rate = 2 kN/h); (**c**) drained (loading rate = 2 kN/day); and (**d**) dry soil (loading rate = 2 kN/step).  
The variation of the excess pore-water pressure generated in the porous soil media has a direct effect on the bending moment and lateral displacement of the piles. Under the undrained loading condition, the values of the lateral displacement and bending moment generated at the end of the incremental loading (i.e., \(t=100\) s), which corresponded to the maximum excess pore-water pressure, were the minimum among all the values observed in the three loading conditions, while for the drained loading case, the lateral displacement and bending moment were the maximum among all the loading conditions. This result implies that the effect of consolidation or dissipation of excess pore-water pressure on the responses of the piles can not be ignored, in particular, for the long-term performance of laterally loaded single piles.  
For each of the loading conditions studied and among the three geometries of the pile and pile cap (cap width, cap embedment depth, and pile length), the width of the pile cap seemed to have the most influence compared to the other two geometries. In this study, the pile length does not seem to have any effect at all on the responses of the laterally loaded single piles.  
Conceptualization, A.A.A. and M.-W.G.; numerical analysis, A.A.A.; writing (first draft preparation), A.A.A.; writing (review and editing), M.-W.G. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors' gratitude goes to the reviewers for their helpful comments and constructive suggestions in improving this paper. The second author is grateful to Taipei Tech for providing the International Graduate Student Scholarship for his study.  
The authors declare they have no conflicts of interest.