黏土中桩靴插拔对邻近三桶导管架基础的影响研究

Research on the Influence of Pile Shoe Insertion and Removal on the Neighboring Three-Cylinder Jacket Foundation in Clay

[目的]移动式平台进场安装海上风机的插拔桩施工过程风险大,易影响邻近基础结构的工作性能,甚至导致其失稳破坏。[方法]为厘清桩靴插拔过程对临近基础的影响机理,文章针对类矩形桩靴,采用CEL大变形方法,开展了其在均质和非均质黏土中插拔过程模拟,重点分析了插桩过程对邻近导管架基础产生的附加倾覆角演变机理;并基于大变形模拟结果,利用小变形进一步研究了桩靴拔出后土体软化效应对邻近桶各向极限承载力的影响。[结果]研究结果表明,在桩靴挤土作用下,三桶导管架基础均会发生先顺后逆的转动位移,且随着净间距的增加而逐渐减小。同时,挤土导致的土体软化会使邻近桶各向承载力降低。[结论]受插拔桩靴的影响,非均质土中的三桶导管架的倾覆角度更大,所对应的贯入深度更深。插拔桩靴所造成的软化区域影响范围在均质黏土中水平方向延伸较大,深度方向较小。在均质黏土中,平均强度损失较小,三桶导管架的水平向、转角向的承载力损失较少。在均质和非均质黏土中,竖向承载力折减明显,最大折减系数可达0.72。

[Introduction]The construction process of pile insertion and removal for installing offshore wind turbines on mobile platforms is risky,which can easily affect the working performance of adjacent infrastructure,and even lead to its instability and failure.[Method]In order to clarify the mechanism of the influence of pile shoe insertion and removal on adjacent foundation,this paper used CEL large deformation method to simulate the insertion and removal process of similar rectangular pile shoe in homogeneous and heterogeneous clay,and focused on the analysis of the evolution mechanism of additional overturning angle caused by pile insertion process on adjacent jacket foundation;based on the simulation results of large deformation,the influence of soil softening effect on the ultimate bearing capacity of adjacent buckets after pile shoe removal was further studied by using small deformation.[Result]The results show that under the action of pile shoe compaction,the rotational displacement of the three-cylinder jacket foundation will take place,and it will decrease gradually with the increase of net spacing.At the same time,the soil softening caused by compaction will reduce the bearing capacity of adjacent cylinder.[Conclusion]The overturning angle of three-cylinder jacket in heterogeneous soil is larger and the corresponding penetration depth is deeper due to the influence of pile shoe insertion and removal.The affected area of softening area caused by pile shoe insertion and removal is larger in horizontal direction and smaller in depth direction in homogeneous clay.In homogeneous clay,the average strength loss is small,and the horizontal and angular bearing capacity loss of the three-cylinder jacket is small.In homogeneous and heterogeneous clays,the vertical bearing capacity is reduced obviously,and the maximum reduction factor can reach 0.72.