插桩过程对临近平台桩基础的影响研究

由于大型自升式钻井船的插桩位置通常距离海上钻井与采油平台较近,桩靴的插入过程可能会对临近平台的桩基础承载力和稳定性产生不利影响。以实际工程为背景,运用球孔扩张理论推导挤土效应产生的水平附加应力大小及其范围;提出一种近似考虑动力挤土效应的拟静力数值模拟方法,分析桩靴下沉到不同深度处时的桩基承载力、桩身应力和最大水平位移,并与静力分析结果进行对比。研究表明,桩靴插入过程对周围土体产生巨大的挤压和扰动作用,使得桩基承载力降低,桩身应力变大,最大水平位移增加;与静力法计算数值相比,由挤土效应导致的单桩承载力下降6%~8%,桩身应力增大30%~80%,桩身最大变形量增长1倍。

Influence of Spudcan Penetration on Pile Foundations near a Platform

Fixed offshore platforms and jack-up drilling platforms can be constructed at the same time because of the development of new jack-up vessels and construction techniques.Unfortunately,a side effect may occur on the pile foundations of the fixed platform when the spudcan penetrates nearby.It is very difficult to simulate the whole dynamic process by a finite-element method.This paper primarily solves the formula of the squeezing soil effect using ball cavity expansion theory.On the basis of the analytical solution,a new pseudo-static method is proposed,which can approximately take the dynamic effect into account.It is analyzed for the bearing capacity,mises stress,and maximum horizontal displacement of pile foundations at different spudcan penetration depths based on an actual project.The simulation results are contrasted with the simple static simulation method.The comparison shows that the bearing capacity is 6%~8% lower than the static simulation result,the Mises stress is 30%~80% higher,and the maximum horizontal displacement is two times larger.