大直径钢管桩土塞效应的拟静力判断方法

钢管桩在贯入过程中土塞效应的正确判断对打桩阻力及承载力的预测有重要影响,常用的静力平衡土塞效应判断方法主要适用于小直径钢管桩。随着海洋平台工作水深的不断增加及海上风电工程的建设,直径大于2m的大直径钢管桩被广泛采用,管桩直径的增加改变了桩管内土体的受力与变形特征。通过数值模拟方法获得砂土中不同径长比的钢管桩在打桩过程中桩周土体的破坏模式,确定采用梅耶霍夫公式计算打桩过程中桩端土体阻力,同时分析锤击惯性力对桩管内土塞的影响,提出采用拟静力平衡法判断大直径钢管桩的土塞闭塞效应。开展不同径长比管桩的室内小比尺打桩模型试验,并对实际工程中的土塞闭塞效应进行判断,验证拟静力平衡法对判断大直径钢管桩土塞效应的适用性。

Quasi-static Method to Evaluate the Soil Plug Effect ona Large-diameter Steel Pipe Pile

During pile driving, soil plug effect evaluation has an important influence on the prediction of pile driving resistance and bearing capacity. The static equilibrium method is usually applied to determine the plugging status of a steel pipe pile with a small diameter. Steel pipe piles that are larger than 2 m have been widely used to increase the operating water depth of offshore platforms and to construct offshore wind projects. The stress and deformation characteristics of soil in pile tube change with the increase of pile diameter. Soil failure mode in the process of driving in sand, with steel pipe piles of different diameter to length ratios is obtained by using numerical simulation method. Based on the numerical simulation result, the Meyerhof formula is determined to calculate the soil resistance. To examine the soil plug effect of a large-diameter steel pipe pile, the quasi-static equilibrium method is proposed, in which the influence of the inertia force on soil plug is analyzed. According to the small-scale pile driving model tests with different diameter to length ratios and the analysis of practical piling project, the applicability of the quasi-static equilibrium method for a large-diameter steel pipe pile is verified.