Screw piles are well-suited foundations for offshore jacket structures, as they can be installed without significant underwater noise and have a large axial capacity. However, installation requirements for such large piles must be reduced to enable their installation in the field. This study combines geometry and installation optimisation to lower force and torque installation requirements. An original pile geometry, composed of a large diameter upper section connected to a smaller diameter lower section by a transition piece, was tested in a geotechnical beam centrifuge. The advancement ratio (AR), describing the relative vertical movement per pile rotation, was varied below the threshold usually recommended. The results show that a low AR reduces the pile penetration resistance and even generates some pull-in, while the torque remains almost unaffected. The torque is mainly associated with the upper section of the pile, which has a greater diameter to resist lateral loading in service. The pile capacity in tension generally increases as AR is reduced and reaches a maximum for AR = 0·5, while the compressive capacity reduces. It was shown that a simplified method can be used to estimate pile capacity, providing that some AR-dependent reduction factors can be calculated or assumed.

中文翻译：

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中密沙中海上导管架地基的优化螺旋桩设计

螺旋桩非常适合海上导管架结构的基础，因为它们可以在没有明显水下噪音的情况下安装并且具有大的轴向承载力。然而，必须降低对这种大型桩的安装要求，以便能够在现场进行安装。本研究结合几何形状和安装优化来降低力和扭矩安装要求。在土工梁式离心机中测试了原始桩几何结构，该桩几何结构由一个大直径的上部部分通过过渡件连接到一个较小直径的下部部分组成。描述每次桩旋转的相对垂直运动的推进比 (AR) 变化低于通常推荐的阈值。结果表明，低 AR 会降低桩的穿透阻力，甚至会产生一些拉入，而扭矩几乎不受影响。扭矩主要与桩的上部有关，桩的直径较大，以抵抗使用中的横向载荷。桩的受拉承载力通常随着 AR 的减小而增加，并在 AR = 0·5 时达到最大值，而抗压承载力则减小。结果表明，可以使用简化的方法来估计桩容量，前提是可以计算或假设一些与 AR 相关的缩减因子。