Uplift resistance of winged composite piles with surplus soil backfill: Model experiments and numerical validation

This study presents a comprehensive experimental and numerical investigation of uplift resistance characteristics in winged composite pile foundations designed to utilize construction surplus soil, addressing Japan's critical construction waste management challenges where on-site utilization remains at only 54.3%. The novel composite system integrates steel structural members (liner plates) surrounding steel pipe piles with expanded base wings, with the annular space filled with construction surplus soil. Through 35 model-scale uplift tests examining seven distinct configurations, the study systematically evaluated effects of steel structural member presence, soil density variations (12 and 15 kN/m3), and surface irregularities across five expanded base wing diameters (32–64 mm). Results demonstrate that uplift resistance increases proportionally with expanded base wing diameter across all configurations, with the composite system achieving performance comparable to or exceeding conventional steel pipe piles under optimal conditions. Soil density emerged as a critical parameter, with 20% density reduction causing approximately 50% decrease in uplift resistance, emphasizing the importance of compaction quality control. Corrugated steel structural members enhanced resistance by 12–13% through improved frictional engagement. Finite element method analyses of three selected cases validated experimental trends, confirming qualitative agreement despite quantitative differences attributable to simplified material parameters. The study provides integrated design guidelines combining experimental and numerical findings, contributing to practical implementation of winged composite pile foundations for wind-load-resistant structures while achieving substantial utilization of construction surplus soil, thereby addressing both structural and environmental imperatives in geotechnical engineering.