Tall structures like radio towers experience high wind loads that generate uplift forces at their foundations, a challenge that is increasing burden, as natural occurrences like typhoons and tornadoes become more frequent and severe. Transmission towers, telecommunication masts, and solar power installations are especially susceptible because uplift forces, rather than compressive forces, influence the foundational stability. On the other hand, the construction industry faces obstacles managing surplus excavated soil, a part of which is used on-site while the rest is usually transported elsewhere for disposal, which increases costs and environmental risks. The combined effects of these pressures have highlighted the need for foundation systems that simultaneously enhance wind resistance and allow more effective on-site soil utilization.
To tackle these challenges, a group of researchers led by Professor Shinya Inazumi from Shibaura Institute of Technology, Japan, investigated a winged composite pile foundation system engineered to provide uplift resistance along with the structural reuse of construction surplus soil. The study, made available online on February 1, 2026, and will be published in Results in Engineering journal on March 1, 2026, evaluates whether foundations combining the use of excavated soil can achieve uplift capacities comparable to conventional steel piles while reducing reliance on imported backfill materials. Prof. Inazumi says, "We observed projects where wind demands were increasing, yet large volumes of potentially usable soil were being treated as waste. That gap in understanding motivated us to explore a foundation system that could address both issues together."
The winged composite pile consists of a steel pipe with expanded base wings, surrounded by steel structural components such as liner plates. The annular space between the steel pipe and the surrounding structural members is filled with surplus soil generated on site. To understand uplift behavior, the researchers conducted a series of 35 model-scale uplift tests covering seven pile configurations. These experiments examined the influence of expanded base wing diameter, soil density, the surface characteristics of the steel components, and the presence or absence of liner plates on uplift resistance. In addition to the physical tests, finite element method (FEM) analyses were performed for selected cases to assess whether numerical simulations could replicate the trends observed experimentally.
The results showed a consistent increase in uplift resistance with larger expanded base wing diameters across all configurations. This relationship was observed regardless of soil density or pile type, indicating that wing geometry plays a dominant role in uplift capacity. In certain conditions, the winged composite pile achieved uplift resistance comparable to, or even exceeding, that of conventional steel pipe piles, demonstrating the effectiveness of surplus soil when used as a part of the load-resisting system. Prof. Inazumi explains, "Winged composite piles filled with surplus construction soil can provide uplift resistance comparable to or greater than that of conventional steel pipe piles. These piles allow the large-volume, on-site reuse of excavated soil, contributing to structural safety and environmental sustainability in wind-resistant foundations. Our tests revealed that uplift capacity increased with an expanded base wing diameter across all configurations."
An important finding was that soil density was identified as a critical factor influencing uplift resistance. A reduction in soil density of approximately 20% resulted in an average decrease in uplift resistance of about 50%. This significant reduction emphasizes the importance of compaction control when surplus soil is used as a structural material.
Additionally, the study also demonstrated that the surface characteristics of the surrounding steel components affect uplift resistance. Corrugated liner plates provided an increase in uplift capacity of approximately 12%–13% compared to smooth steel components. This was attributed to enhanced frictional resistance and mechanical interlocking between the soil and the steel components. FEM analysis was also carried out to examine whether numerical simulations could reproduce experimental trends.
Explaining the applications of the winged composite pile system, Prof. Inazumi explained, "Our findings can be directly applied to the foundations of infrastructures that must withstand strong wind uplift such as transmission towers, radio towers, telecommunication masts, and solar power facilities built on sandy ground. Our system provides an alternative for these structures, offering uplift capacities comparable to or higher than those of conventional steel pipe piles while reducing the need for imported, high-quality backfill materials."
By integrating experimental findings from FEM analyses, the researchers proposed design guidelines associating uplift resistance to expanded base wing diameter and soil density. The study establishes winged composite piles as a foundation system that combines uplift resistance with large-volume, on-site reuse of construction surplus soil, addressing both structural requirements and surplus oil utilization requirements.
Reference
DOI: https://doi.org/10.1016/j.rineng.2026.109404
About Shibaura Institute of Technology (SIT), Japan
Shibaura Institute of Technology (SIT) is a private university with campuses in Tokyo and Saitama. Since the establishment of its predecessor, Tokyo Higher School of Industry and Commerce, in 1927, it has maintained "learning through practice" as its philosophy in the education of engineers. SIT was the only private science and engineering university selected for the Top Global University Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology and had received support from the ministry for 10 years starting from the 2014 academic year. Its motto, "Nurturing engineers who learn from society and contribute to society," reflects its mission of fostering scientists and engineers who can contribute to the sustainable growth of the world by exposing their over 9,500 students to culturally diverse environments, where they learn to cope, collaborate, and relate with fellow students from around the world.
Website: https://www.shibaura-it.ac.jp/en/
About Professor Shinya Inazumi from SIT, Japan
Dr. Shinya Inazumi is a Professor in the College of Engineering at Shibaura Institute of Technology (SIT), Japan, and leads the Geotechnical Engineering Laboratory, where research focuses on sustainable ground and infrastructure solutions. He received his Ph.D. in Engineering from Kyoto University. His research interests span civil and geotechnical engineering, geo-disaster mitigation, and AI-applications in infrastructure planning. As an established author with hundreds of publications, he has also been recognized with prestigious awards for research excellence in geotechnical and environmental engineering.
