复杂环境中大规模桩筏基础的优化设计方法研究

变刚度优化设计对于复杂环境中的大规模桩筏基础始终是一个重要难题。基于有限元分析提出一种两阶段优化设计方法，该方法首先根据传统均匀布桩方案的桩顶应力分布对群桩进行分区，然后依据每个子区域桩顶应力之间的关系确定基桩数量调整系数，最后通过调整桩间距来改变各子区域的基桩数量，从而实现变刚度优化设计。运用该方法对多层土体中承担非均匀上部结构荷载的大规模桩筏基础进行变刚度优化设计，计算结果表明优化设计后筏板的差异沉降、平均整体弯矩和群桩顶部的差异应力均显著降低。该方法计算简单，应用范围广，且不受复杂土层条件、非均匀上部结构荷载以及桩基础规模大小形状的限制。

Research on optimization design method of large-scale pile-raft foundation in complex environment

Variable stiffness optimization design is always an important and difficult problem for large-scale pile-raft foundations in complex environments. In this article, a two-stage optimization method was developed using finite element analysis, According to the stress distribution on top of piles in the traditional design with uniform pile arrangement, the pile groups are divided into several sub-groups firstly. Then the adjustment coefficient of the number of piles is determined according to the relationships among the pile top stresses of every sub-group. Finally, by adjusting the spacing of piles to change the number of piles in each sub-group, the variable stiffness optimization design can be realized. This procedure is used to optimize the large-scale piled raft foundations with non-uniform superstructure loads in multi-layer soils. The results show that after optimal design, the differential settlement of the raft, the average overall bending moment and the differential stress at the top of the pile are significantly reduced. The method is simple in calculation and wide in application, and is not limited by complex soil conditions, non-uniform superstructure loads and the size and shape of the pile foundation.