自升式平台插桩过程CEL分析及验证

CEL Analysis and Verification on Penetration Process of Jack-up Spudcan

插桩对自升式平台总体响应和设计影响很大,插桩预测有助于保证平台安全工作和减少刺穿事故。本文采用欧拉-拉格朗日耦合法(CEL)研究桩靴在粘土中的插桩性能。土体采用三维减缩积分欧拉单元离散,并定义为von-Mises弹性塑性模型;桩靴简化为刚体,其与土体间的相互作用采用加强沉浸边界法模拟。与Hossain所做的土工离心模型试验对比表明:von-Mises模型可以有效模拟出插桩过程中土体的流动特性,与试验模型所得结果吻合良好;在插桩过程中,土体发生了表面隆起、壁面坍塌、土体回流和局部流动等4种流动失效现象;Skempton方程忽视了土体部分回流对桩靴承载力的影响,在插桩前期预测结果偏大,后期与数值解一致。

Penetration has much effect on the whole response and design of jack-up. The prediction of the penetration process could assure its safe work and reduce punch-through failure. Coupled Eulerian-Lagrangian （CEL） approach was presented to investigate spudcan penetration into clay, which was validated by geotechnical centrifugal model test, proposed by Hossain. In the numerical model, 3D Eulerian elements with reduced integration was adopted to discretize soil with von-Mises elastic plastic model, rigid body was used to simulate spudcan, and en- hanced immersed boundary method was imposed on the interaction between spudcan and soil The results showed that, von-Mises model could effectively simulate the soil flow mecanism, agreeing well with the experimental results. Soil flow failures, such as surface heave, wall collapse, soil back-flow and localized flow, were found in the penetration process. Skempton equation neglected parted back-flow of soil, which resulted in high initial prediction, but agreed well with the numerical results in the late stage.