冲刷后地基土体特性及平台桩基承载力研究

摘要

Due to the effect of wave, tide, water flow and storm surge, erosion may take place around the pile foundation of offshore fixed platform. Erosion reduces the horizontal and longitudinal bearing capacity of pile foundation. Evaluation of the effect of erosion on the foundation usually adopts the method which removes the scoured soil layer and assumes that the physical property of subsoil remains unchanged. However, the method ignores the stress progress difference of soil body before and after erosion which causes the changes of soil mass property. The bearing capacity property of platform pile foundation was studied on the basis of the change of soil property of sand soil foun- dation due to the effect of erosion. The friction angle, relative density and overconsolidation rate of sand foundation soil mass after erosion were estimated. Thereby the calculation formula for sand foundation limit soil resistance after e- rosion was proposed and the p-y curve of pile foundation soil resistance after erosion was modified. Finally, the SACS 5.2 software was adopted to explore and analyze the dynamic response of lateral loaded pile after erosion. The findings show that neglect of the change of soil property after erosion may lead to too conservative design of lateral loaded pile.%评价冲刷对桩基础的影响常采用将冲刷掉的土层直接移去且认为下层土体物理特性不变的方法。该方法忽略了冲刷前后土体经历的应力历程的差异及由此导致的土体特性变化。基于冲刷作用下砂土地基土体特性的变化,对平台桩基承载力性状进行了研究。对冲刷后砂土地基土体的摩擦角、相对密度和超固结率进行了估算。在此基础上提出冲刷后砂土地基极限土抗力计算公式,并对冲刷后桩基土抗力p-y曲线进行了修正。最后利用SACS 5.2软件分析冲刷后横向受载桩的动力响应。分析结果表明,忽略冲刷后土体特性的变化可能会导致横向受载桩过于保守的设计。