Experimental and Numerical Investigations on Finned Pile Foundations Subjected to Lateral Loads

Abstract

This thesis presents an innovative finned pile foundation system as an alternative to regular pile foundations to resist larger lateral loads and improve pile group efficiency. The work presented in the thesis is an effort toward achieving the global targets set through Sustainable Development Goals (SDGs), particularly SDG#9 (Industry Innovation and Infrastructure) and SDG#11 (Sustainable Cities and Communities) by reducing the carbon footprints through the reduction in usage of carbon-intensive materials for infrastructure. It is proposed to make an innovative alteration to the regular piles to meet the infrastructure requirements with less usage of concrete and steel. This work evaluates the lateral load resistance of finned piles for onshore foundation applications. It compares their performance under seismic excitation with regular pile mats for high-rise buildings and wind turbines. In addition to physical model experiments, the numerical studies were performed in a FEM framework. Physical model experiments for individual long piles embedded in c–φ soil were conducted on scaled-down models, and the load-displacement behaviour was studied. The study presented the influence of fin factors such as fin position, width, length, orientation, embedment in pile cap, and eccentric loading and suggested the optimum fin parameters to increase the lateral resistance to the maximum.The findings demonstrated that finned piles, which had fins embedded in pile caps, exhibited superior performance compared to regular piles lacking fin embedment. The cost-benefit study supported the construction economy with finned piles, using only 55% of the material used by regular piles. In an effort to enhance the lateral resistance of pile groups, this study explored the implementation of innovative finned piles. The research examined the influence of multiple factors, such as fins, the quantity of piles (n), pile spacings (s), and their behavior when subjected to eccentric loading. The results showed that FP-groups have a higher lateral resistance than RP-groups, resulting in improved pile group efficiency of up to 185%. The study found that pile spacing is more influential than the number of piles. A cost-benefit analysis compared the finned pile groups to regular pile groups. Additionally, regression analyses were performed to establish a correlation that enables i the calculation of the lateral resistance of finned pile groups based on different fin parameters. Furthermore, this study places emphasis on mitigating the adverse effects of earthquakes, wind forces, dredging activities, and machine vibrations on multi-story buildings that are supported by piled mats. The study aims to minimize vibrations within the structure by using an innovative finned-pile foundation system, which can withstand 65% to 80% higher lateral load than conventional pile systems. The seismic responses of a 25–story building resting on a finned-pile mat were studied in the FEM framework through time–history analysis for varying fin lengths. The findings indicated that incorporating finned–pile mats had a notable impact in reducing vibrations and seismic effects on the building. It was suggested that an optimal fin length of 0.6Lp would effectively balance both seismic performance and construction efficiency for finned–pile mats. Furthermore, the study investigated the potential of utilizing finned-pile mats (FP-Mat) as a foundation system to enhance the performance of wind turbines when subjected to seismic excitation. The study used finite element method (FEM) modelling to perform time–history analyses on wind turbines resting on piled mats under different earthquake excitations, considering soil–structure interaction. The results showed that FP–Mat with a fin length of 0.5m reduced the vibration by 27% compared to regular–pile mat (RP–Mat) and reduced the wind turbine’s segmental drift within acceptable limits. The FP–Mat was also found to reduce the tower’s tilting by 30%–40% under seismic excitation, reducing the risk of collision between the tower and blades, leading to a more sustainable design strategy. Overall, the study emphasized the need for careful assessment of the seismic performance of wind energy harvesting devices in an earthquake–prone regions and the potential benefits of using Finned Pile–Mat as a sustainable and alternative foundation system.