基于三维离散元的大直径钢圆筒下沉侧摩阻力

Side Friction of Large-Diameter Steel Cylinder Simulated Using 3D Discrete Element Method

基于三维离散元方法(DEM),采用颗粒流程序(PFC3D)对大直径钢圆筒在砂土中的贯入过程进行了数值模拟分析。分别建立了基于离心机原理的缩尺模型和调整细观参数的足尺模型,分析了圆筒贯入过程中的侧壁摩阻力分布以及土颗粒间的接触关系。将数值结果与理论值、相关试验现象进行对比,验证了离散元模型的有效性。通过进一步的参数分析,研究了不同细观参数对侧摩阻力的影响。研究发现:与桩的贯入机制不同,大直径钢圆筒下沉过程中几乎没有土塞效应;内侧摩阻力接近总侧摩阻力的一半,侧摩阻力均存在侧阻疲劳效应;与缩尺模型相比,调整细观参数的足尺模型有更高的计算效率;细观参数与宏观反应存在密切联系。

The penetration process of the large-diameter steel cylinder in sandy soil was stimulated with a three-dimensional particle flow code(PFC3 D) based on the discrete element method(DEM). A scaled model based on the principle of the centrifuge and a full-scale model with adjusting the micro-parameters were developed to analyze the sliding friction force distribution of the cylinder during installation and the contact force chain of soil particles. The DEM model was validated by comparing the simulated results with theoretical values and reported experimental phenomena. The effects of micro parameters of particles and contacts on side friction were studied through further parametric analysis. The study results show that, unlike pile penetration, there is almost no soil-plug effect during penetration process of large-diameter steel cylinder. Besides, the inside friction is half of the total friction, and the side friction has the effect of friction fatigue during installation. Compared with the scale model, the full-scale mo-del with adjustable micro-parameters has better calculation efficiency. There is a close relationship between the side friction and micro parameters.