Abstract Spudcan retrieval from clay soils remains a major concern offshore as the extraction force required to overcome suction and soil resistance often exceeds the pulling capacity available on the mobile jack-up, causing extensive delays. Although methods to calculate extraction resistance have been recently suggested for seabeds of pure clay, to date there is no guidance available for the commonly encountered sand-over-clays. Based on failure mechanisms observed in half-spudcan visualisation tests, and calibrated against an extensive geotechnical centrifuge database of precisely measured extractions, this paper presents a method for calculating the force required to extract the spudcan foundations of mobile jack-up platforms after they have penetrated through a sand layer into underlying clay. Complexities, such as the strength degradation and strength recovery of the underlying clay soil, that occurs during spudcan installation and jack-up operations, are accounted for. Validation of the proposed method is demonstrated by retrospective prediction of the centrifuge testing database. The method outlined will allow operators of jack-up platforms to assess the extraction force prior to jack-up installation and to plan operational scenarios based on seabed conditions.

中文翻译：

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从砂覆粘土海床上自升式桩靴提取所需的突围力

摘要 从粘土中取出 Spudcan 仍然是海上的一个主要问题，因为克服吸力和土壤阻力所需的提取力通常超过移动式自升式平台上可用的牵引能力，从而导致大量延误。尽管最近有人提出了用于计算纯粘土海床提取阻力的方法，但迄今为止，还没有针对常见的砂覆盖粘土的指导。基于在半桩柱可视化测试中观察到的失效机制，并根据精确测量提取的广泛岩土离心机数据库进行校准，本文提出了一种计算移动自升式平台桩基钻入后提取桩基所需力的方法穿过沙层进入下面的粘土。复杂性，例如，在桩腿安装和自升式作业期间发生的下伏粘土的强度下降和强度恢复都被考虑在内。通过对离心机测试数据库的回顾性预测证明了所提出方法的有效性。概述的方法将允许自升式平台的操作员在自升式安装之前评估提取力，并根据海床条件规划操作方案。