Surplus Construction Soil Can Replace Conventional Fill in Wind-Resistant Foundations

Two Problems, One Potential Solution

Construction projects generate enormous volumes of excavated soil. Much of it gets trucked away and disposed of at cost, even when the material could theoretically serve a structural purpose at the very site where it was dug. Meanwhile, transmission towers, radio masts, and solar installations face growing pressure from an intensifying climate -- hurricanes, typhoons, and extreme wind events that generate uplift forces capable of pulling foundation elements straight out of the ground.

These two problems have been treated independently. A research group led by Professor Shinya Inazumi at Shibaura Institute of Technology in Japan asked whether they might be solved together. The answer, published in Results in Engineering (March 2026), is a qualified yes -- with important caveats about execution.

The Winged Composite Pile

The foundation system under study combines two elements. At its core is a standard steel pipe pile. Around it, steel structural members such as liner plates form a cylindrical enclosure. Horizontal "wings" at the pile's base extend outward, enlarging the bearing area against the soil. The annular space between the central pipe and the surrounding steel members is filled with surplus soil from the construction site itself -- not imported, graded fill.

Uplift resistance in pile foundations comes from two mechanisms: end bearing (the wings pressing against overlying soil as the pile is pulled upward) and skin friction (resistance between the pile surface and surrounding soil). The winged composite system exploits both, with the expanded base wings being the primary design variable.

What 35 Tests Revealed

The team conducted 35 model-scale uplift tests spanning seven pile configurations. Variables included expanded base wing diameter, soil density, surface roughness of the steel components, and the presence or absence of corrugated liner plates. Finite element simulations were run in parallel to validate whether numerical models could predict observed behavior accurately.

Wing diameter was the dominant factor. Across all configurations, regardless of soil density or liner plate type, larger expanded base wings produced higher uplift resistance in a consistent relationship. At the best-performing configurations, the winged composite piles filled with surplus soil achieved uplift capacities matching or exceeding those of solid conventional steel pipe piles -- the current industry standard.

"Winged composite piles filled with surplus construction soil can provide uplift resistance comparable to or greater than that of conventional steel pipe piles," said Inazumi. "These piles allow the large-volume, on-site reuse of excavated soil, contributing to structural safety and environmental sustainability in wind-resistant foundations."

Soil Density Is the Critical Variable

One finding stands out as an important engineering constraint. A 20% reduction in soil density caused approximately a 50% drop in uplift resistance. That is a steep sensitivity. It means that the performance gains from using surplus soil depend heavily on controlling compaction during construction. Loosely placed surplus material cannot simply substitute for properly managed structural fill; it must be actively compacted to a specified density.

Corrugated liner plates -- steel components with ridged surfaces rather than smooth ones -- provided 12% to 13% higher uplift capacity than smooth alternatives. The researchers attribute this to increased friction and mechanical interlocking between soil and steel.

The research was conducted at model scale in uniform sandy material; mixed or cohesive soils may behave differently. Field validation studies in actual construction conditions will be needed before broad adoption in structural specifications.