宁海特大桥不等长桩基础问题探析

Analysis of the Problems of the Unequal Length Pile Foundation of the Specially Long Span Bridge in Ninghai

根据宁海特大桥桩基础的实际情况,阐述不等长桩基础的存在性。从地壳运动、河床变迁、洪潮影响及桥位土层分布四个角度分析造成桩长差异的原因。基于m法,分析计算多排桩及单排桩情况下不等长桩基础的内力和变形情况。结果表明:因不等长桩基础导致桩基础几何中心、弹性中心和扭转中心不重合,不等长度桩基和等长度桩基在受力特点上存在较大差异;讨论改善桩长差异的措施,如调整嵌岩深度和其他边设计边施工的方法,但措施基本停于理论,应进一步从理论提升简单必要的构造措施加以改善。

According to the real situation of the pile foundation of the specially long span bridge in Ninghai,the existence of pile foundation with different length is discussed. The reasons are analyzed from four aspects： crustal movement,river-bed evolution,the influence of flood and tide,soil layer distribution. Based on M method,the internal force and deformation of unequal pile foundation under the condition of multi-row piles and single-row piles are studied and calculated. Results showed that there are differences on mechanical characteristics between the unequal length and the equal length pile foundation,because the geometric center,the elastic center and the torsion center of the unequal length pile foundation are not coincident. Moreover,the measures to improve the difference of pile length have been proposed,such as adjusting the depth of embedded rock and other methods designed during construction,but the measures basically stopped at the theory stage,more research should focus on the necessary structural measures upgrading from theory.