海上自升式钻井平台插桩阶段桩靴承载力计算

为了准确预测海上自升式钻井平台插桩阶段贯入深度，引入流-固耦合理论，建立了饱和黏土条件下土-桩靴系统的有限元模型，利用该模型对桩靴贯入均质与非均质黏土时的桩靴承载力系数进行了数值计算。结果表明，桩靴承载力系数的大小主要取决于土体强度和桩靴贯入深度：对土体强度非均匀系数较低的土体，桩靴承载力系数与桩靴贯入深度正相关，而土体强度非均匀系数较大的土体桩靴承载力系数与桩靴贯入深度呈负相关；当桩靴贯入深度为20 m左右时，桩靴的极限承载力系数为10.30（不考虑土体回流作用）和12.25（考虑土体回流作用）。给出了插桩过程中桩靴承载力的计算方法，并利用此方法计算了渤海5号平台在特定土质条件下桩靴的贯入深度，提出的计算方法由于考虑了整个插桩过程中土-桩靴相互作用、土体的非线性特性、桩靴底面的端阻力和桩靴侧面阻力等影响，预测的桩靴贯入深度更为合理，与传统计算方法的结果相差20%左右。图9表2参25

Spudcan bearing capacity calculation of the offshore jack-up drilling platform during the preloading process

To predict the penetration depth of the offshore jack-up drilling platform during the preloading process, the fluid-solid coupling theory was introduced. The limited element model of the earth-spudcan system under saturated clay was established. With this model, the spudcan bearing capacity coefficient was numerically calculated when spudcans penetrating into homogeneous and heterogeneous clay. The result showed that, the spudcan bearing capacity coefficient is mainly decided by the earth strength and spudcan penetration depth, as for earth with lower strength heterogeneous coefficient, the spudcan bearing coefficient has a positive correlation with the spudcan penetration depth, while for earth with higher strength heterogeneous coefficients, the correlation is negative. When the spudcan penetration depth is about 20 m, the maximum bearing capacity coefficient of spudcan is 10.30 (not consider earth backflow) and 12.25 (consider earth backflow), respectively. The calculation method for spudcan bearing capacity during the preloading process was given. With this method, the penetration depth of spudcan under certain earth condition for the 5th platform in the Bohai Sea was calculated. Because the proposed calculation method considered the influences of reaction between earth and spudcan, the nonlinear property of earth, end resistance at the bottom of spudcan and lateral resistance of spudcan during the whole preloading process, thus the predicted spudcan penetration depth is more reasonable, and has the difference of about 20% with the result of traditional calculation method.