【作者】 黄晋；

【导师】 王国才； 卢成原；

【作者基本信息】 浙江工业大学 ， 结构工程， 2009， 硕士

【摘要】 在港口、桥梁和近海平台等工程中的桩基础,主要是用来承受斜向荷载,而不仅仅是承受水平或竖向荷载。在斜向荷载作用下桩的工作机理及性状的研究时,通常是将斜向荷载分解成竖向和水平荷载,然后将二者分开单独计算桩的响应,再按小变形叠加原理合并其计算的内力和位移,并在桩身截面强度验算时将截面弯矩乘以一修正系数加以修正。目前,关于斜向荷载作用下竖直桩的工作机理及性状的研究成果还很少。为更进一步了解斜向荷载作用下基桩的工作性能,本文通过室内模型试验研究了水平荷载对竖向承载桩、竖向荷载对水平承载桩以及斜向荷载分别作用下单桩承载性状和荷载传递机理,并用有限元法对斜向受荷的单桩和群桩进行了数值模拟,其主要工作和结论如下:(1)简单概述了桩基的发展历史和竖向受荷桩、水平受荷桩与竖向-水平同时受荷桩国内外的研究现状和成果。(2)对斜向受荷桩进行了室内模型试验。通过模型桩试验研究,分析了水平荷载对竖向承载桩沉降及桩身弯矩的影响、竖向荷载对水平承载桩水平位移及桩身弯矩的影响以及按同比例同时施加水平和竖向荷载时,水平荷载对桩沉降的影响。(3)通过有限元分析软件ABAQUS 6.5对斜向受荷桩进行了数值模拟与分析。在分析过程中,对桩周土分别采用弹性和修正Cam-clay模型以模拟土体的非线性,而桩-土接触面则设置了接触单元以考虑桩与土的滑移和开裂。通过不同计算模型和不同荷载组合作用分析了水平荷载对竖向承载桩的沉降、竖向荷载及偏心竖向荷载对水平承载桩的水平位移以及倾斜荷载的倾角对桩顶的沉降、水平位移和桩身挠度的影响。(4)通过数值模型,进一步分析了水平荷载对竖向承载桩沉降的影响,竖向荷载对水平承载桩挠度的影响以及不同倾角的倾斜荷载对桩身的挠度和弯矩的影响,并将所得数值模拟结果与某工程的实测结果进行对比分析,结果表明两者拟合较好。(5)对不同大小和倾角的倾斜荷载作用下的群桩内力、位移和弯矩等进行了数值模拟与分析。结果表明:荷载大小及倾角对桩身弯矩的影响较大,边桩的存在可减小中桩的侧阻力。由于群桩效应使得两边桩对中桩有遮拦作用,并导致中桩的弯矩有所降低。更多还原

【Abstract】 Pile foundations, such as those used in ports, bridge and offshore platforms and so on, are mainly subjected inclined loadings, not only vertical or horizontal loadings. The inclined loadings are usually divided into vertical and horizontal loadings when the mechanism and properties of piles under inclined loadings are investigated. Then, the pile response is studied under individual loading and the inner force and displacement can be calculated according to the superposition principle of small deformation. The cross section moment is modified by multiplying a modified coefficient when checking the cross section strength. At present, little research work has been done on the mechanism and behavior of vertical pile under inclined loadings.In order to further investigate the behavior of piles under inclined loadings, the experimental model tests has been done to reveal the loading ability and loading transfer mechanism of single vertical bearing piles under horizontal loading, horizontal bearing piles under vertical loading and vertical piles under inclined loading. Then, the behaviors of single piles and pile groups under inclined loadings are analyzed using numerical simulation. The main c??nt of this paper can be summarized as follows:(1) A brief introduction on the history of development in pile foundations, and the research status and results at home and abroad of piles under vertical loading, lateral loading or coupled vertical-lateral loading are discussed.(2) Some laboratory model tests are made of piles under inclined loadings. With the aid of experimental study of model piles, it is revealed the effects of lateral loading on the settlement and moment of vertical-bearing piles, the effects of vertical loading on the horizontal displacement and moment of horizontal-bearing piles and the effect of horizontal loading on the settlement of piles by increasing horizontal and vertical loadings under same loading ratio.(3) The behavior of inclined-loading pile is numerically simulated and analyzed using finite element analysis software ABAQUS 6.5. In the analysis, the soil nonlinear is simulated using elastic and modified Cam-clay models, respectively. The contact elements around the pile-soil interface are set to represent the slippage and separation of pile-soil system. By means of different calculation model and different loading combinations, the effects are investigated of lateral loading on the vertical-bearing pile’s settlement, of vertical loading and eccentric vertical loading on the lateral-bearing pile’s lateral displacement and of inclined loading with different inclination angle on the vertical pile’s settlement, lateral displacement and flexibility.(4) The effects are further analyzed of lateral loading on the settlement of vertical-bearing piles, vertical loading on the flexibility of horizontal-bearing piles and inclined loading with different inclination angle on the pile’s flexibility and moment. The numerical results obtained are compared and analyzed with the field testing results, which indicates that they agree very well.(5) The internal ??e, displacement and moment of group piles are studied under different loading magnitude and inclination angle using numerical simulation and analysis. Based on the results obtained, it is found that the magnitude and inclination angle of loading have a great influence on the pile’s moment, and the existing of side piles can reduce the friction of middle piles. On account of group piles effects, side piles have a role of impede on the middle piles, which can further reduce the middle pile’s moment at a certain extent.更多还原