【作者】 王宁伟；

【导师】 赵振东；

【作者基本信息】 中国地震局工程力学研究所 ， 岩土工程， 2006， 博士

【摘要】 复合地基的理论与应用是目前土木工程中比较活跃的研究领域。近十多年来,复合地基技术得到了较大的发展。由于复合地基中设置的增强体不同,因此,各类复合地基的承载机理也不完全相同。本文对于碎石桩复合地基和刚性桩复合地基的承载特性、设计方法及工程应用等进行了较系统的研究。1.综述了复合地基的发展和研究现状,指出了复合地基存在的主要问题。2.对现有散体材料桩复合地基极限承载力计算、沉降计算方法进行了总结,并讨论了散体材料桩复合地基设计的一般方法。3.在作者大量的工程实践的基础上,建立了碎石桩复合地基的抗液化评价和承载能力评价的工程方法。在利用瑞利波速度评价天然地基液化判别的基础上综合考虑碎石桩体的应力集中作用和桩体的排水作用,给出了碎石桩复合地基在不同抗震设防烈度下的液化判别的方法;建立了以工程中常用的动触试验、瑞利波法评价碎石桩桩体质量的方法;给出了复合地基承载力、桩土应力比、变形模量的工程计算方法,并与传统的静载试验方法进行了对比,能够较充分地满足工程的需要。4.讨论了刚性桩复合地基的设计原理、设计思想。通过作者对CFG单桩复合地基的现场静载试验得到了桩土应力比、桩土荷载分担比的变化规律;对刚性桩复合地基褥垫层的作用机理进行了分析,并建议工程中设置褥垫层的合理厚度。5.用FLAC3D有限差分程序建立单桩复合地基数值分析模型,分别研究了桩间土模量、桩端土模量、垫层厚度、垫层模量、桩长、置换率及桩体弹性模量对CFG桩复合地基沉降、桩端沉降、垫层压缩量及桩土应力比的影响,对于复合地基工程设计和施工具有指导意义。6.利用广义平面应力问题的轴对称解答,分别考虑垫层侧限和土体侧限状态,推导出桩顶处垫层压缩量的计算方法。应用Boussinesq解及拉压模量不同的弹性理论解,假定侧摩阻力与桩土相对位移为理想弹塑性关系,进一步推导出一种新的考虑桩-土-垫层相互作用的刚性桩复合地基沉降计算的修正不同模量法。更多还原

【Abstract】 The theories and the applications of composite foundation are quite activethe research direction in civil engineering field at present. The nearly more thanten for years, the technology of composite foundation have obtained biggerdevelopment. Because the composites reinforced in composite foundation aredifferent, therefore, the load bearing mechanism of each kind of compositefoundation is not all the same.In this paper, the bearing characteristics, the design methods and theengineering applications of the gravel pile and the rigid pile compositefoundations are carried on systematic research.1. The development and the research present situation of compositefoundation are summarized and the extant main questions of compositefoundation are pointed.2. The ultimate bearing capacity, settlement calculation methods of theexisting Granular Columns composite foundation are carried on the summaryand the general design methods of the existing Granular Columns compositefoundation are discussed.3. Based on the massive projects practices of author, the comprehensiveproject appraisal methods about anti-liquefaction appraisals and bearing capacityappraisals of the gravel piles composite foundation are established. On the basisof Using Rayleigh wave velocity to evaluate liquefaction judgment of naturalground, comprehensive consider the effect of stress concentration and verticaldrains action of gravel piles. The liquefaction judgment methods of the gravelpiles composite foundation are given in the different earthquake resistance;based on the commonly used methods in project, such as dynamic sounding testand Rayleigh wave method, the methods that evaluate the pile body quality ofgravel piles are established. The engineering calculation methods about bearingcapacity, pile-soil stress ratio and deformation modulus of composite foundationare given, contrast with the conventional static load test method and the methodsof this paper completely satisfy the requirement of actual projects.4. The design principles and philosophies of rigid pile compositefoundation are discussed. The change rules of pile-soil stress ratio and pile -soilbearing load ratio are obtained through the field static loading test of CFG pilecomposite foundation. The mechanisms of cushion of rigid pile compositefoundation are analyzed and the cushion reasonable thicknesses in projects aresuggested.5. Single pile composite foundation numerical analysis model is establishedby utilizing general FLAC3D finite differential program, the soil around pilesmodule, soil under the pile module, cushion thickness, cushion module, pilelength, replacement ratio and pile body elastic modulo are influential tosettlement, soil under the pile settlement, compression of cushion and pile-soilstress ratio of the CFG foundation, these influences have been separately carriedon the research, has the instruction significance to the engineering design andthe construction of the composite foundation.6. Used the axial symmetry explanation of generalized the plane stressproblems, separately considered the lateral confinement of soil and cushion, thecalculation methods of cushion compression of pile top are deduced. AppliedBoussinesq’s solution and the elastic theory solutions which are different moduloin tension and compression, supposed friction resistance along the pile anddisplacement of pile-soil are ideal elastic-plastic relations, a new revise thedifferent molds method that calculate the settlement of rigid pile compositefoundation is deduced, this method considers interaction of pile-soil-cushion.7. The multi-piles composite foundation load bearing character and actionmechanism of composite piled raft foundation have been carried on the analysis.8. The working performance under horizontal load and the seismic loadingof the rigid pile composite foundation are analyzed, the rigid pile compositefoundation has an excellent anti-seismic characteristics.更多还原