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<p>While screw-shaft piles are widely used in fine-grained soils, their application in coarse-grained soils remains limited.Coarse particles make the pile-soil interaction more complex and obscure the load transfer mechanism, leading to considerable errors in existing calculation methods. To address this gap, based on a practical project, this study takes gravelly soil as a typical coarse-grained soil and systematically investigates the vertical bearing performance of a single screw-shaft pile. Drawing on a real-world engineering project, a numerical model is established and subsequently validated by laboratory model tests. Numerical simulations are conducted to analyze the load transfer mechanism, soil displacement distribution, and the effects of pile length, pile diameter, thread segment ratio, thread width, and thread pitch on bearing characteristics. The results demonstrate that under ultimate conditions, the influence radius of soil displacement is about 1D–2D at the pile side and 1D at the tip (D = pile diameter). As pile length increases from 800&#xa0;mm to 1400&#xa0;mm, the ultimate bearing capacity increases by 20.2%–69.9%. As pile diameter increases, bearing capacity improves but material utilization decreases; a smaller diameter saves material. When the thread segment ratio is 30%–40%, pile-soil interlocking is significant, the surrounding soil is efficiently utilized, and stress concentration at the variable cross-section is not pronounced. When the thread width is about 0.2D, side resistance is better mobilized and bearing capacity is significantly improved. When the thread pitch is about 1D, material utilization reaches its maximum. Mechanism analysis reveals that the significant increase in bearing capacity of the screw-shaft pile mainly results from the substantial increase in side resistance in the threaded section (approximately 79% of the total load at ultimate state), rather than from tip resistance, which differs markedly from the “friction‑end bearing combined” mode of the conventional straight pile (side resistance ≈ 56%, tip resistance ≈ 44%). Collectively, these findings provide a theoretical basis for designing and applying screw-shaft piles in coarse-grained soil regions.</p>

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Research on Vertical Bearing Characteristics of Screw-Shaft Pile in Gravelly Soil

  • 期刊论文

  • 发表日期：

    2026年7月22日

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  • Yaqin Chen,
  • Cheng Chen,
  • Xiaowu Ma,
  • Lichen Liu,
  • Hongguang Zhang

摘要

While screw-shaft piles are widely used in fine-grained soils, their application in coarse-grained soils remains limited.Coarse particles make the pile-soil interaction more complex and obscure the load transfer mechanism, leading to considerable errors in existing calculation methods. To address this gap, based on a practical project, this study takes gravelly soil as a typical coarse-grained soil and systematically investigates the vertical bearing performance of a single screw-shaft pile. Drawing on a real-world engineering project, a numerical model is established and subsequently validated by laboratory model tests. Numerical simulations are conducted to analyze the load transfer mechanism, soil displacement distribution, and the effects of pile length, pile diameter, thread segment ratio, thread width, and thread pitch on bearing characteristics. The results demonstrate that under ultimate conditions, the influence radius of soil displacement is about 1D–2D at the pile side and 1D at the tip (D = pile diameter). As pile length increases from 800 mm to 1400 mm, the ultimate bearing capacity increases by 20.2%–69.9%. As pile diameter increases, bearing capacity improves but material utilization decreases; a smaller diameter saves material. When the thread segment ratio is 30%–40%, pile-soil interlocking is significant, the surrounding soil is efficiently utilized, and stress concentration at the variable cross-section is not pronounced. When the thread width is about 0.2D, side resistance is better mobilized and bearing capacity is significantly improved. When the thread pitch is about 1D, material utilization reaches its maximum. Mechanism analysis reveals that the significant increase in bearing capacity of the screw-shaft pile mainly results from the substantial increase in side resistance in the threaded section (approximately 79% of the total load at ultimate state), rather than from tip resistance, which differs markedly from the “friction‑end bearing combined” mode of the conventional straight pile (side resistance ≈ 56%, tip resistance ≈ 44%). Collectively, these findings provide a theoretical basis for designing and applying screw-shaft piles in coarse-grained soil regions.