【摘要】 自升式钻井平台完成钻井作业后,需要进行拔桩操作。历史上发生的多起自升式平台拔桩事故都与在特定地质条件和入泥深度下平台的拔桩能力评价相关,而其中拔桩阻力预测的偏差是重要的因素。文中分析自升式平台拔桩阻力的影响因素,用通用有限元软件Abaqus对拔桩过程进行数值计算,实现对拔桩过程中桩土相互作用、孔隙水与桩周土体的流固耦合作用及桩周土体的重新回落、淤积、固结等的数值模拟,得到拔桩过程中桩周土体的变形、破坏等运动规律,进而得出平台在特定孔位、特定入泥深度下的拔桩阻力。数值分析与规范公式计算的结果对比发现,公式计算所得结果偏大,主要是因为公式计算将各部分阻力(桩靴底部吸附力、桩靴侧面摩擦阻力、桩靴上部覆土的重力和桩侧土体的剪切破坏力)取最大值相加所得,而实际过程中各部分拔桩阻力并非同时达到最大值。文中的数值计算方法弥补了现有公式计算的不足,为进一步评定平台拔桩能力及结构强度的设计提供一种较为准确的计算方法。更多还原

【Abstract】 After completion of the drilling operation,uplift operation will be followed to pull out the jack-up units from the seabed.Many accidents arising from uplift operation have taken place causing severe damages of the legs or even hulls of the units.One of the main problems is the error of prediction of the uplift capacity of jack-up units in specific soil conditions and specified penetrations.A parametric study with numerical analysis on the uplift capacity is performed by using the Abaqus,and the spudcan-soil reaction,the coupling of pore water and soil,and the cohesion and consolidation of the soil,etc.have been comprehensively investigated to reveal the process of deformation and collapse of the soil around the spudcan.The comparison of the numerical results with those by rules demonstrates that the overestimation of uplift resistance value by formula from the rules is mainly because that the sum of all the components is based on every maximum value of all components of spudcan bottom suction force,side friction,weight of soil above spudcan,and shear resistance,which will never occur at the same time in the actual process.The numerical method presents a better and more accurate solve for calculating the uplift capacity,and displays the nature of uplifting process.更多还原