超高层建筑超长桩群桩与厚筏基础受力沉降机理研究

For the super-high rise building with the structural system of core shear wall and giant column outer frame, stress and settlement mechanisms of the super-long pile group and thick raft foundation will be studied by methods of model test, numerical simulation and theoretical analysis. Bearing behaviors and pile-soil-pile interaction mechanisms of the super-long pile group, stress and settlement characters of the thick raft, load characteristics of the foundation soil between piles, and influence laws of the upper structure on the pile-raft foundation will be acquired by means of large-scale model test in combination with numerical simulation analysis. Based on the actual project, integrity FEM numerical models of the super-long pile group and thick raft foundation with the upper structure will be established. Then, the influence of the raft thickness, pile slenderness ratio and pile layout on stress and settlement of the pile-raft foundation will be researched. Besides, according to the analysis of bearing behaviors and pile-soil interface shear mechanisms of the super-long pile, a pile-soil interface shear model will be presented. Then, pile stiffening effect on the soils and sheltering effect between passive piles and soils are taken into account to analyze and calculate pile-soil-pile interaction. Moreover, Burmister solution of multi-layered elastic half-space is applied to consider the variation of layered soil properties. Reissner thick plate theory is adopted for the thick raft calculation. The influence of the stiffness the building upper structure is also considered. According to these, a theoretical calculationmethod will be established to analyze the stress and settlement mechanisms of the super-long pile group and thick raft foundation. All of these researches can help in-depth understand the bearing and settlement behaviors of the super-long pile group and thick raft foundation for the super high-rise building, and promote the development of design calculation method of the pile-raft foundation.

针对采用核心筒巨柱外框架结构体系的超高层建筑超长桩群桩与厚筏基础，通过大尺度模型试验结合数值模拟研究超长桩群桩承载性状及桩-土-桩相互作用机理、厚筏基础受力变形性状、地基土体受荷特征、及上部结构对桩筏基础的影响规律；同时，基于实际工程建立超高层建筑超长桩群桩与厚筏基础整体有限元模型，研究筏板厚度、基桩长径比与布置等因素对其受力沉降变形的影响；此外，基于超长桩承载特性、桩侧摩阻力发挥机理及桩-土界面剪切力学行为的研究，建立超长桩桩-土界面剪切作用模型，并在考虑桩体的“加筋效应”及群桩中的“被动桩”与周围土体的相互“遮拦效应”对桩土相互作用影响的基础上，引入层状地基Burmister解、Reissner厚板理论及上部结构刚度的影响，建立超高层建筑超长桩群桩与厚筏基础受力变形理论计算分析方法。本项目研究有助于深入认识超高层建筑桩筏基础承载变形性状，促进其安全合理的设计与实施。

以采用核心筒巨柱外框架结构的超高层建筑超长桩群桩与厚筏基础为研究对象，基于其上部结构、筏板、基桩及地基土体间的相互作用机制，深入研究分析其受力与沉降变形机理。通过现场实测及模型试验深入研究超长桩承载性能、荷载传递规律及相关因素的影响规律等，并建立相关荷载传递模型及桩侧广义剪切模型，进行超长桩荷载传递计算；开展超长桩群桩基础模型试验，研究超长桩群桩基础承载变形规律及其荷载传递机理，得到荷载-沉降规律、桩身轴力分布、桩侧摩阻力、筏下土承担荷载、桩端土应力和桩间土反力分布规律，并对超长群桩桩-土相互作用及荷载传递性状进行探讨；基于实际工程，开展考虑上部结构影响的超长桩群桩厚筏基础数值模拟分析，研究其沉降变形规律及上部结构对其沉降变形的影响；基于弹性半空间的Mindlin位移解的数值积分，结合叠加原理的Poulos 弹性理论方法，提出考虑群桩加筋效应三桩模型方法及加筋系数的概念，建立考虑遮拦-群桩加筋效应的群桩加筋系数分析法，并对超长群桩进行沉降分析。研究成果将有助于超高层建筑桩筏基础承载性状的认知，促进超高层建筑桩筏基础工程实践的发展。