饱和土中桩基的水平动力特性研究
发布时间：2019-02-16 11:43
【摘要】：由于桩基沉降量小、抗震性能好及承载能力高等优点而被广泛应用于桥梁工程、高层建筑和海洋平台等众多工程领域。在动荷载作用下,桩基础的稳定性取决于桩的工作性能,而桩基的工作性能是桩与其周围土之间的动力相互作用的结果,目前,部分埋入桩的振动和完全埋入桩基的瞬态响应研究还仅限于单相介质,然而土又是由固液气组成的三相介质,研究饱和两相介质无疑更接近客观实际、更具有工程实际价值。因此,本文在博士学科点专项科研项目等项目基金的资助下,对饱和土中部分埋入桩基的水平振动特性和饱和土中完全埋入桩基的瞬态响应进行展开研究。 本文将土体视为饱和两相多孔介质,运用Biot固结理论来描述饱和土的力学性能,利用Novak薄层法,引入势函数解耦,求得层状饱和土半空间位移和应力基本解,利用桩-土变形协调条件和桩单元间位移、转角、弯矩和剪力的连续性条件建立了桩身刚度矩阵方程,导出了水平稳态谐振下部分埋入单桩阻抗函数的封闭形式解答。利用层状饱和土半空间位移建立衰减函数,构筑被动桩的控制方程,同样采用矩阵传递法求得到相互动力作用因子,采用迭代法原则建立群桩矩阵方程,最后求解高承台群桩矩阵方程得到群桩的动力阻抗。并以双层饱和土中部分埋入单桩和3x3高承台群桩基础为例,分析了埋入比、桩间距、渗透系数和土层模量比等参数对群桩阻抗的影响。 通过对Biot动力固结方程无量纲化和Laplace变换,先引入势函数进行解耦,通过算子分解和分离变量法,得到均质饱和土Laplace域内的位移,并以此建立Laplace域内的衰减函数,基于Winkler模型,联立振动微分方程,推导了Laplace变换域内单桩和群桩位移函数及单桩内力表达式。最后采用Laplace逆变换的优化模型求得了时域内瞬态响应的封闭解。参数分析结果表明：桩土模量比、长径比、渗透系数对单桩水平位移均影响显著,而长径比超过一定值后则影响较小,且桩土模量比是影响桩身弯矩和剪力大小及其分布的重要参数。 图36幅,表2个,参考文献145篇
[Abstract]:Because of the advantages of small settlement, good seismic performance and high bearing capacity, pile foundation has been widely used in many engineering fields, such as bridge engineering, high-rise building and offshore platform. Under the dynamic load, the stability of the pile foundation depends on the working performance of the pile, and the working performance of the pile foundation is the result of the dynamic interaction between the pile and the surrounding soil. The study of the vibration of partially buried pile and the transient response of completely buried pile foundation is limited to single-phase medium, but the soil is a three-phase medium composed of solid, liquid and gas, so the study of saturated two-phase medium is undoubtedly closer to the objective reality and has practical engineering value. Therefore, the horizontal vibration characteristics of partially embedded pile foundation and the transient response of fully embedded pile foundation in saturated soil are studied in this paper, supported by the special scientific research project of doctorate. In this paper, the soil is regarded as a saturated two-phase porous medium, the mechanical properties of saturated soil are described by Biot consolidation theory, and the basic solution of displacement and stress in half-space of layered saturated soil is obtained by introducing potential function decoupling by Novak thin-layer method. In this paper, the stiffness matrix equation of pile body is established by using the compatibility condition of pile and soil deformation and the continuity conditions of displacement, rotation angle, bending moment and shear force between pile elements, and the closed form solution of impedance function of partially embedded single pile under horizontal steady state resonance is derived. The attenuation function is established by using the half-space displacement of layered saturated soil, and the governing equation of passive pile is constructed. In the same way, the interaction factor is obtained by matrix transfer method, and the matrix equation of pile group is established by iterative principle. Finally, the dynamic impedance of pile group is obtained by solving the matrix equation of pile group with high cap. The effects of embedding ratio, pile spacing, permeability coefficient and soil modulus ratio on pile group impedance are analyzed with the example of partially embedded single pile and 3x3 high cap pile group foundation in double-layer saturated soil. Through dimensionless and Laplace transformation of Biot dynamic consolidation equation, the potential function is introduced to decouple, and the displacement in Laplace domain of homogeneous saturated soil is obtained by operator decomposition and separation variable method, and the attenuation function in Laplace domain is established based on Winkler model. The displacement function of single pile and group pile and the expression of internal force of single pile in Laplace transform domain are derived by simultaneous vibration differential equation. Finally, the closed solution of transient response in time domain is obtained by using the optimization model of Laplace inverse transformation. The results of parameter analysis show that the pile-soil modulus ratio, the ratio of length to diameter and permeability coefficient have significant effects on the horizontal displacement of single pile, but when the ratio of length to diameter exceeds a certain value, the influence is small. The pile-soil modulus ratio is an important parameter that affects the bending moment, shear force and distribution of pile. 36 figures, 2 tables, 145 references
【学位授予单位】：中南大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU473.1
本文编号：2424411
[Abstract]:Because of the advantages of small settlement, good seismic performance and high bearing capacity, pile foundation has been widely used in many engineering fields, such as bridge engineering, high-rise building and offshore platform. Under the dynamic load, the stability of the pile foundation depends on the working performance of the pile, and the working performance of the pile foundation is the result of the dynamic interaction between the pile and the surrounding soil. The study of the vibration of partially buried pile and the transient response of completely buried pile foundation is limited to single-phase medium, but the soil is a three-phase medium composed of solid, liquid and gas, so the study of saturated two-phase medium is undoubtedly closer to the objective reality and has practical engineering value. Therefore, the horizontal vibration characteristics of partially embedded pile foundation and the transient response of fully embedded pile foundation in saturated soil are studied in this paper, supported by the special scientific research project of doctorate. In this paper, the soil is regarded as a saturated two-phase porous medium, the mechanical properties of saturated soil are described by Biot consolidation theory, and the basic solution of displacement and stress in half-space of layered saturated soil is obtained by introducing potential function decoupling by Novak thin-layer method. In this paper, the stiffness matrix equation of pile body is established by using the compatibility condition of pile and soil deformation and the continuity conditions of displacement, rotation angle, bending moment and shear force between pile elements, and the closed form solution of impedance function of partially embedded single pile under horizontal steady state resonance is derived. The attenuation function is established by using the half-space displacement of layered saturated soil, and the governing equation of passive pile is constructed. In the same way, the interaction factor is obtained by matrix transfer method, and the matrix equation of pile group is established by iterative principle. Finally, the dynamic impedance of pile group is obtained by solving the matrix equation of pile group with high cap. The effects of embedding ratio, pile spacing, permeability coefficient and soil modulus ratio on pile group impedance are analyzed with the example of partially embedded single pile and 3x3 high cap pile group foundation in double-layer saturated soil. Through dimensionless and Laplace transformation of Biot dynamic consolidation equation, the potential function is introduced to decouple, and the displacement in Laplace domain of homogeneous saturated soil is obtained by operator decomposition and separation variable method, and the attenuation function in Laplace domain is established based on Winkler model. The displacement function of single pile and group pile and the expression of internal force of single pile in Laplace transform domain are derived by simultaneous vibration differential equation. Finally, the closed solution of transient response in time domain is obtained by using the optimization model of Laplace inverse transformation. The results of parameter analysis show that the pile-soil modulus ratio, the ratio of length to diameter and permeability coefficient have significant effects on the horizontal displacement of single pile, but when the ratio of length to diameter exceeds a certain value, the influence is small. The pile-soil modulus ratio is an important parameter that affects the bending moment, shear force and distribution of pile. 36 figures, 2 tables, 145 references
【学位授予单位】：中南大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU473.1
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