【作者】 刘从友；

【导师】 刘高；

【作者基本信息】 兰州大学 ， 岩土工程， 2009， 硕士

【摘要】 针对当前复合地基沉降计算理论和方法的不足,依托郑西客运专线湿陷黄土地基处理现场实体试验,基于工程地质学和复合地基桩土共同作用原理,以挤密桩复合地基为例,以实测沉降变形监测资料为依据和校核标准,综合采用理论分析、数值试验和数值计算,分析了挤密桩复合地基沉降变形特征,探讨了复合地基作用机理,研究了复合地基的复合模量,讨论了复合地基沉降的计算方法。以实测地基沉降变形为依据,对复合地基沉降变形展开研究。(1)采用基于正交设计的数值试验方法,分析了复合地基沉降变形计算的影响因素(破坏准则、材料参数、置换率、桩形和计算方法),其中材料参数和置换率对地基沉降变形影响较大。(2)综合实体试验挤密桩试验区实测沉降变形、数值试验和数值计算,对复合地基桩土作用机理进行探讨。复合地基作用机理体现在复合地基位移场和应力场分布特征上,表现为3区(复合地基区、复合地基外围天然地基区和下卧层区)分布,各区的应力分布特征以及变形特征不完全相同,应力呈“竖向条状横向相间”分布,桩体和桩间土体在上部荷载作用下相互影响,桩土协调变形并共同承担上部荷载。复合地基作用机理取决于桩体和桩间土体的力学性质差异程度,桩土模量差异越大,复合地基中桩土作用机理越复杂,反之越简单。(3)针对复合地基复合模量,以实测沉降变形为依据和校核标准,采用复合式数值计算方法,得出复合地基复合模量与桩体、桩间土体之间为非线性关系公式,也表明了复合地基作用机理的复杂性。(4)湿陷性黄土地区复合地基沉降计算,采用分离式数值计算方法、复合式数值计算方法和分层总和法讨论了复合地基的沉降变形,只要选取合理的复合模量,采用简单的复合式数值计算方法可获得与实测沉降变形基本相同的计算结果。通过对湿陷性黄土地区挤密桩复合地基作用机理和沉降计算方法的研究,在立足于桩土作用机理的基础上,合理的选取复合地基沉降计算方法,可对地基的合理设计提供依据。更多还原

【Abstract】 This article makes an analysis on the settlement characteristics of compaction pile composition foundation, probes into the principle of composite foundation, makes a studying on the complex modulus of the foundation, and discusses the calculation methods of composite foundation, because of the shortcomings of the current theories and methods of settlement calculation. The study relies on the scene entity tests in the disposal of collapsible loess foundation along on the Zhengzhou-Xi’an Passenger Line, bases on the engineering geology and the principle of the combined pile-soil effect of the composite foundation, takes the compaction pile composite foundation as an example, the measured settlement data as an basis and check standards, and adopts the methods of theoretical analysis numerical experiment and numerical calculation.The basis of study on the settlement of composite foundation is measured foundation settlement. (1) The numerical methods base on the orthogonal design has been used to analyze the influencing factors of the settlement calculation of the composite foundation, among which material parameters and replacement rate have larger impact on the foundation settlement. (2) The discussion has been made on the composite foundation by combining the measured settlement, numerical experiment and numerical calculation in the entity-test compaction piles test area. The characteristics of the displacement field and stress field distribution are the embodiment of the action mechanism in the composite foundation. The distribution has three areas, the characteristics of the stress distribution and deformation in each area are not exactly the same, the stress is distributed with the characteristics of "strip in the vertical direction and alternation in the horizontal direction", there is interaction between piles and the soils among piles under the upper load, piles and soils distorts in the coordination, sharing the upper load together. The action mechanism of composite foundation depends on the differences extent of the mechanical properties between the piles and the soils among them, the greater the difference of pile-soil modulus, the more complex of the action mechanism in the composite composition, contrarily, the simpler. (3) Taking the measured settlement as a basis and calibration standard, using the separate calculation method, the non-linear relationship expression between the complex modulus and piles and soils among piles has been drawn, which shows the complexity of the action mechanism of the composite foundation. (4) The separate numerical calculation method, composite numerical calculation method and layer wise summation method have been used to calculate the settlement in the composite foundation in the collapsible loess areas to discuss the settlement in the composite foundation. A calculation result is essentially same to the measured settlement, when using a simple composite numerical calculation method, as long as a selection of a reasonable complex modulus.Through the study on the action mechanism and the settlement calculation method of the composite foundation in the collapsible loess areas, a reasonable selection of calculation method for the composite foundation provide a basis for the rational design of the foundation, based on the foundation of the action mechanism on piles and soils.更多还原