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<p>This study develops a <i>c</i>–<i>φ</i> soil computational model to quantify the installation torque during helical pile deployment, incorporating both proportional (pitch-matched) and non-proportional (overflighted) drilling modes. The model systematically investigates the mechanisms governing installation torque generation, which arises from resistance components including the anchor shaft, upper/bottom helix surfaces, helix outer edge, and soil within the pitch range. The key findings reveal that a rotational speed below 20&#xa0;rpm negligibly affects the torque magnitude, while proportional drilling demonstrates dominant resistance contribution (&gt; 50% of total torque) from the helix base, with soil resistance within the pitch range becoming negligible. For non-proportional drilling, the torque escalates inversely with the drilling proportion, peaking at a zero drilling proportion (vane shear test equivalence), where the soil cylinder resistance matches the helix base resistance. The experimental validation confirms strong agreement between the measured torque profiles and the model predictions across diverse geological conditions. Furthermore, a crowd pressure model accounting for differential soil pressures on helix surfaces is established: the field measurements show excellent correlation with the calculated values at shallow depths, while crowd force stabilization occurs at penetration depths ≥ 5 times the helix diameter (5<i>B</i>) due to the pile self-penetration effects. This integrated framework provides a theoretical foundation for optimizing construction parameters and enhancing helical pile performance across heterogeneous soil strata.</p>

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Theoretical and Experimental Investigation of Torque and Crowd Force on Helical Piles in c – φ Soil

  • 期刊论文

  • 发表日期：

    2025年5月24日

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  • Songzhao Qu,
  • Yonghua Guo,
  • Quan Zhang

摘要

This study develops a c–φ soil computational model to quantify the installation torque during helical pile deployment, incorporating both proportional (pitch-matched) and non-proportional (overflighted) drilling modes. The model systematically investigates the mechanisms governing installation torque generation, which arises from resistance components including the anchor shaft, upper/bottom helix surfaces, helix outer edge, and soil within the pitch range. The key findings reveal that a rotational speed below 20 rpm negligibly affects the torque magnitude, while proportional drilling demonstrates dominant resistance contribution (> 50% of total torque) from the helix base, with soil resistance within the pitch range becoming negligible. For non-proportional drilling, the torque escalates inversely with the drilling proportion, peaking at a zero drilling proportion (vane shear test equivalence), where the soil cylinder resistance matches the helix base resistance. The experimental validation confirms strong agreement between the measured torque profiles and the model predictions across diverse geological conditions. Furthermore, a crowd pressure model accounting for differential soil pressures on helix surfaces is established: the field measurements show excellent correlation with the calculated values at shallow depths, while crowd force stabilization occurs at penetration depths ≥ 5 times the helix diameter (5B) due to the pile self-penetration effects. This integrated framework provides a theoretical foundation for optimizing construction parameters and enhancing helical pile performance across heterogeneous soil strata.