穿刺压载试验及桩-土空腔数值模拟

Punch-through ballast experiment and numerical simulation of pile and soil cavity

基于穿刺压载试验,采用ABAQUS/ALE有限元分析方法模拟自升式平台插桩过程,对桩土贯入过程中空腔的作用机理进行数值分析,通过监测桩下、土体表面和桩侧附近土体点位移的时程变化,研究空腔的作用机理.数值模拟结果表明：空腔破坏严重加大桩端承载;桩靴底部土体回流造成空腔垂直壁面剪切破坏是空腔形成及其深度发展的主要原因.针对桩靴穿刺现象,利用穿刺压载试验对数值模拟进行验证.结果表明：数值解与试验结果吻合;穿刺发生时,桩端承载骤降,桩靴外侧压力约为内侧压力5～10倍,压力变化呈非线性分布,这与中国船级社《海上移动平台入级与建造规范》中关于桩靴底部压力呈线性分布假定不符.

Based on punch-through ballast experiment,the pile penetration process of jack-up platform was simulated by using ABAQUS/ALE finite element method. Cavity mechanism numerical simulation in pile and soil penetrating process was studied by monitoring the time course changes of soil point displacement at spudcan bottom,soil surface and spudcan rim. Numerical simulation results indicate that the spudcan bearing increases distinctly when the cavity failures,and the shear failure of the vertical cavity wall resulted from the back-flow of soil under spudcan is the main reason resulting in cavity formation and progress. Numerical simulation results of punch-through phenomenon were verified by punch-through ballast experiment. Test results show that the numerical solution concide well with test. When punch-through occurs,the spudcan bearing sharp fall off and the outside spudcan pressure is almost 5 ～ 10 times to the inside,and pressure change appears the non-linear distribution,which is not coincided to the liner assumption in ＂Rules for the classification and construction of offshore mobile drilling units＂of CCS.