层状地层中自升式钻井平台桩脚稳定性分析

影响自升式钻井平台桩脚在层状地层中的稳定性主要是穿刺。穿刺主要发生于上部为硬土层但下部为软弱层的层状地层体系中。文章重点介绍了用于穿刺分析的两种方法,推导了计算公式,并在实例中作了应用,得到了较为一致的结果。实例中两种计算方法得到的桩脚稳定性系数为0.3~0.5,插桩深度约7.1m,与实际插桩深度较为吻合。考虑了下卧软弱层影响下的上覆硬土层的承载力计算方法既可判断穿刺可能性又能得到插桩深度,是一种简便易行的方法。同时对影响桩脚在地层中稳定性的冲刷作用和动荷载作了提示,以便在进行平台桩脚的稳定性评价时予以综合分析。

Footing Stability of Jack-up Rig in the Layered Soil

Punch-through is the main factor that affects the footing stability of jack-up rig in the layered soil. Geological condition that can cause a footing to experience a punch-through failure includes sand or strong clayey soil layer of limited thickness overlying a weaker clayey soil layer. The paper introduces two methods to obtain the possibility of punch-through failure and deduces the equation of calculation. The two methods are applied in one case that shows the result is consistent. In this case, the factor of stability based on different calculation method varies from 0.3 to 0.5 and the footing penetration is about 7. 1m, which approaches the actual penetration. It is recommended to calculate the ultimate bearing capacity of a strong stratum overlying a weaker clayey layer in order to evaluate the possibility of punch-through failure and footing penetration. Other factors affecting the footing stability such as scour and dynamic load are also discussed.