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<p>The compressive capacity of single helical piles in various cohesionless soils was investigated using 3D numerical analysis (PLAXIS 3D) and validated against a full-scale load test in northern Alberta, Canada, showing strong agreement. An extensive parametric study determined the influence of the pile’s geometric parameters on compressive capacity, adopting a 5%<i>D</i> settlement failure criterion.The study examined these parameters within the two failure mechanisms: cylindrical shear (CS) and individual bearing (IB). The results indicated that the critical interhelix ratio ranges from 1.50 to 1.60 for loose sand, 2.85–2.90 for medium dense sand, and 2.95–3.00 for dense sand. It was demonstrated that increasing the interhelix ratio, wing ratio, number of helices, embedment ratio, and soil relative density consistently enhanced compressive capacity.Comparisons revealed that conventional theoretical equations significantly overestimate capacity. Consequently, a modified approach is proposed, limiting effective overburden pressure used in plate bearing calculation to 5.87D. Verification across 35 models showed 85.71% of the modified equation’s results had less than 50% error, whereas 45.71% of conventional capacities exhibited errors exceeding 100%. RMSE decreased from 1776.47 kN for the original equation to 692.15 kN. Notably, for wing ratios below 2.80 (IB) and up to 3.20 (CS), the proposed equation achieved an RMSE of 301.35 kN, outperforming Perko’s method (676.09 kN). However, the new approach is limited to a single helical pile embedded in homogeneous cohesionless soil with wing ratios below 2.80 for IB and up to 3.20 for CS, subjected to a failure criterion of 5%<i>D</i>.</p>

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Failure Mechanisms of Helical Piles and Evaluation of Capacity Prediction Models

  • 期刊论文

  • 发表日期：

    2026年3月23日

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  • Nader Ibrahim,
  • Sayed M. Ahmed,
  • Mahmoud S. Hammad

摘要

The compressive capacity of single helical piles in various cohesionless soils was investigated using 3D numerical analysis (PLAXIS 3D) and validated against a full-scale load test in northern Alberta, Canada, showing strong agreement. An extensive parametric study determined the influence of the pile’s geometric parameters on compressive capacity, adopting a 5%D settlement failure criterion.The study examined these parameters within the two failure mechanisms: cylindrical shear (CS) and individual bearing (IB). The results indicated that the critical interhelix ratio ranges from 1.50 to 1.60 for loose sand, 2.85–2.90 for medium dense sand, and 2.95–3.00 for dense sand. It was demonstrated that increasing the interhelix ratio, wing ratio, number of helices, embedment ratio, and soil relative density consistently enhanced compressive capacity.Comparisons revealed that conventional theoretical equations significantly overestimate capacity. Consequently, a modified approach is proposed, limiting effective overburden pressure used in plate bearing calculation to 5.87D. Verification across 35 models showed 85.71% of the modified equation’s results had less than 50% error, whereas 45.71% of conventional capacities exhibited errors exceeding 100%. RMSE decreased from 1776.47 kN for the original equation to 692.15 kN. Notably, for wing ratios below 2.80 (IB) and up to 3.20 (CS), the proposed equation achieved an RMSE of 301.35 kN, outperforming Perko’s method (676.09 kN). However, the new approach is limited to a single helical pile embedded in homogeneous cohesionless soil with wing ratios below 2.80 for IB and up to 3.20 for CS, subjected to a failure criterion of 5%D.