高层建筑物桩筏基础内力分布和演化分析

Analysis on Stress Distribution and Evolution of Pile-raft Foundation in Construction of Tall Buildings

通过三维数值计算,研究了高层建筑从基坑开挖到上部结构修筑过程引起的桩筏基础内力分布和演化过程。根据桩筏基础的受力和变形特征,以及桩筏荷载分担比例,讨论桩筏基础和地基土的协同作用效应。计算表明,桩筏基础的内力分布一般受柱子设置位置的控制。在上部建筑物荷载作用下,柱端处会产生较大的弯曲应力。此外,筏板底部处也存在较大的压力,使得桩间土产生明显的压缩变形,亦即限制了桩与土之间的相对位移,进而减小了桩侧摩阻力。因此,在上部荷载修筑的初期,桩的端摩擦阻力起主要作用,然后上部桩的桩侧摩阻力才随上部结构荷载的增大得以逐步发挥作用。

The distribution and evolution of the internal stress on the pile-raft foundation of a tall building in the whole process from the excavation of pit to the construction of superstructure are studied here by the method of three -dimensional numerical calculation .According to the stress and deformation features of pile-raft foundation as well as the shearing ratio of pile-raft load ,the synergy effect of the pile-raft foundation and soil is discussed and analyzed .The calculation results show that he internal stress distribution of pile-raft foundation is controlled mainly by the location of pillar .At the top of pile ,there exists a greater bending moment .There exists an obvious compression between the pile and soil layer due to the stress on the bottom of raft ,which would limit the relative displacement and reduce the fiction on the lateral surface of pile .Therefore ,the bearing capacity of pile is provided mainly by the friction of pile end at primary stage ,and then the friction force in the upper parts of pile is increased progressively with the increase of structural load .