黏土中自升式钻井船插桩对邻近桩基影响的分析方法

自升式钻井船是广泛用于浅、中水域油气资源开发的重要设施，经常紧邻固定式导管架平台进行作业。钻井船插桩就位过程中大量土体被排开，挤土效应会导致邻近导管架平台桩基承受很大的附加荷载，影响平台的正常设计性能，该效应在黏土中尤为显著。针对黏土中钻井船插桩对邻近桩基的影响这一实际问题，现有规范和分析方法存在明显不足。为此，建立了一套数值分析方法，把这一复杂问题分解成相对独立、简单的两个方面进行分析：一是采用任意拉格朗日-欧拉（ALE）数值方法，计算自由场地插桩周围土体产生的位移场；二是利用桩基水平力与位移关系曲线，即P-Y曲线，采用杆系-土弹簧的传统方法计算土体位移产生的桩体加载。通过与已有离心试验数据的比较，验证了该方法的可靠性和适用性。研究揭示了自由场地土体的变形模式和流动机制，阐明了由于插桩邻近桩基产生的附加荷载变化规律，特别是发现了黏土变形参数 对插桩引起的自由场地土体位移场有显著影响，但对插桩引起的桩基加载影响较小。最后，针对导管架对桩基的桩头约束条件和插桩及导管架自身对桩基的线性叠加加载适用性问题给出了详细说明。

An approach to analyze effects of spudcan penetration of a jack-up rig on adjacent piles in cohesive soils

A mobile jack-up rig is an important facility in offshore oil and gas development and often works in close proximity to a permanent jacket platform. Penetration of the spudcan could displace a large volume of soil and induce considerable loadings to the pile foundation of a nearby jacket, which may jeopardize the designated performance of the jacket platform. The aforementioned effect is more significant in cohesive soils where deeper penetration is expected. However, the currently available industry guideline and approaches have obvious limitations on this important issue. Therefore, a numerical approach is developed in this paper which has two steps to study the effects of the spudcan penetration on an adjacent jacket pile in cohesive soils: (1) computation of the lateral soil displacement induced by the spudcan penetration in a free field assuming the jacket is absent through the arbitrary Lagrangian Eulerian (ALE) numerical method, and (2) computation of the pile lateral loading induced by the aforementioned soil displacement based on the P-Y curves by the conventional beam-column method. Feasibility and reasonability of the approach are verified by calculated results against centrifugal experiment results published in the past. The paper reveals the deformation mode and flow mechanism of the soil in the free field, indicates the variation of additional loadings of the adjacent pile induced by spudcan penetration, and especially finds that the induced soil displacement is heavily dependent on soil deformation characteristics such as , and the induced pile loading is found to be not sensitive to the variation of within a reasonable range. Finally, the study discusses how to define the boundary condition at the pile head where the pile is connected to the upper structure, and whether the linear superposition law is appropriate for loadings induced by the spudcan penetration and the jacket.