海洋石油平台桩基拒锤现象

Pile Driving Refusal of Offshore Platform

为了解决在海洋石油平台建造中打入大直径超长桩经常遇到的拒锤问题,采用一维波动方程研究了桩-土-锤体系的相互作用原理,采用弹性力学的小孔扩张理论研究了打桩过程中桩周围土体中的总应力增加量,并用斯开普敦公式计算了由此引起的超静孔隙水压力.应用饱和土的有效应力原理、水力劈裂理论以及土体的固结理论分析了后继打桩桩周土阻力增大甚至出现拒锤现象的原因.结合打桩记录,采用反分析方法确定当后继打桩出现拒锤现象时的单桩承载力.实际工程算例和海上原位动测结果说明了该方法具有可行性。

To solve the problem of refusal after restarting the driving of the piles of large diameter and length in the building of offshore platform, the interaction mechanism of the pile-soil-hammer system was studied using the one- dimensional wave equation. The increment of the total stress in the earth surrounding the pile was studied according to the pore expansion theory of elastic mechanics. Excess pore water pressure caused by this stress increment was computed with the Skempton formula. The causes of the increase in the resistance of earth and the resulting refusal of the restarted pile were analyzed using principle of effective stress in the saturated soil, theory of hydraulic splitting, and theory of soil concretion. The single pile bearing capacity after refusal was predicted by reverse analysis using the historic data of piling. The effectiveness of the method was confirmed by the good agreement between the real case computation and the in situ measurement.