Helical pile (screw pile) is becoming increasingly popular in emerging pile foundation techniques for offshore structures. Its installation parameters (i.e., installation force, torque, and power) are significantly important for design and construction of helical pile foundation. However, there are very limited studies on the installation power of large-diameter multi-helix piles in sand particularly with the consideration of the installation effects of rotary press-in. This paper proposes a new modified method suitable for predicting the installation torque and force of single-helix and multi-helix piles, which involves four aspects of important factors: the installation effect of helical piles, the bidirectional force (i.e., vertical and tangential shear stress) on the side of the central shaft during rotary press-in, the interaction between helices for muti-helix piles, and the vertical installation force (crowd force) effect on torque generation. The proposed and the two existing methods (i.e., Ghaly and Hanna model and Al-Baghdadi model) are used to predict the installation toque and power of helical piles in sand with different relative densities (loose, medium dense, and dense) based on pile geometry characteristics. Predictions from aforementioned three methods are compared with measurements from the centrifugal model tests of various screw piles in sand with the proposed method giving better agreement with the measured data. The calculation from the proposed method also gives closer agreement with field measurements of the double-helix pile than those from existing methods. In addition, it is found that the installation power of helical piles increases nonlinearly with the increase of the relative density of sand (or peak friction angle) and installation force and torque account for about 10% and 90%, respectively, of the total power through the parameter sensitivity analysis.

螺旋桩（螺旋桩）在新兴的海上结构桩基础技术中越来越受欢迎。其安装参数（即安装力、扭矩和功率）对于螺旋桩基础的设计和施工具有重要意义。然而，对于大直径多螺旋桩在砂土中的安装功率，特别是考虑旋转压入安装效果的研究非常有限。本文提出了一种适用于预测单螺旋和多螺旋桩安装扭矩和力的新改进方法，该方法涉及四个方面的重要因素：螺旋桩的安装效果、双向力（即垂直和切向剪力）。旋转压入过程中中心轴一侧的应力），多螺旋桩的螺旋之间的相互作用，以及垂直安装力（人群力）对扭矩产生的影响。利用所提出的方法和现有的两种方法（即 Ghaly 和 Hanna 模型和 Al-Baghdadi 模型）基于桩身预测不同相对密度（松散、中密和密实）沙土中螺旋桩的安装扭矩和功率。几何特征。将上述三种方法的预测与沙中各种螺旋桩的离心模型试验的测量结果进行比较，所提出的方法与测量数据具有更好的一致性。与现有方法相比，所提出方法的计算与双螺旋桩的现场测量结果更接近。此外，