H-T联合作用下基桩内力位移理论分析及试验研究

发布时间：2018-10-13 20:00

【摘要】：近年来,随着我国沿海经济的快速发展,近海大型基础建设(如海上桥梁、海上平台、风力发电塔等)的规模不断扩大。这类多采用桩基础的海上结构物时常承受由车辆制动、风、波浪、地震、船只或漂流物或撞击等引起的水平受荷,且往往以水平偏心的形式传递至桩基础,造成复杂的结构响应。分解这种作用于桩身上的水平偏心荷载即表现为受水平力H和扭矩T的联合作用,工程中若不考虑这种偏心作用,可能会使设计偏于不安全并导致灾难性后果。然而,现行基于叠加原理的常规方法不能考虑这种荷载耦合作用,存在不少尚需解决的问题。为此,本文结合已有相关研究工作,对水平受荷桩、受扭桩及H-T联合受荷桩进行理论分析和室内模型试验研究,主要工作如下:首先,假定桩周土体满足广义Gibson地基分布特性,引入虚土桩理论,基于能量法获得桩-土体系能量控制方程,通过变分原理分别建立出水平荷载作用下桩身和桩侧土的控制方程,进而采用中心点差分法分别导得了桩-土的响应值。在此基础上,假定桩侧土塑性区从地面开展并往下延伸,由此获得桩侧土处于塑性状态时的下桩-土响应值。其次,基于剪切位移法和平衡原理,考虑桩侧土体剪切模量沿深度呈幂函数分布,同时假定桩侧土的塑性变形随桩顶荷载增加自上而下逐步开展,得到纯扭矩作用下桩侧土分别处于弹性、弹塑性和塑性状态时的桩身内力变形解析解。同时,针对工程中地基土的分层特性,引入土体弹塑性受扭荷载传递模型,给出了层状地基中纯受扭桩桩身扭矩-扭转角的计算公式。第三,基于m法和改进有限杆单元法,将水平力H和扭矩T的耦合关系计入杆单元刚度矩阵,得到统一的杆单元刚度方程,并考虑不同边界条件获得H-T联合作用时桩身的内力位移解答。最后,采用自制砂箱和滑轮组加载装置完成了砂土中单桩受纯水平力H、扭矩T及H-T联合作用的室内模型试验,获得了相应的桩顶荷载-变形曲线、桩身内力-位移曲线。
[Abstract]:In recent years, with the rapid development of China's coastal economy, the scale of large-scale offshore infrastructure (such as offshore bridges, offshore platforms, wind power towers, etc.) is expanding. These types of offshore structures, which often use pile-foundations, are often subjected to horizontal loads caused by vehicle braking, wind, waves, earthquakes, ships or drifters or impacts, and are often transmitted to the pile foundation in the form of horizontal eccentricities. Resulting in complex structural responses. Decomposing this kind of horizontal eccentric load on the pile is expressed as the combined action of horizontal force H and torque T. if this eccentricity is not considered in engineering, the design may be unsafe and lead to disastrous consequences. However, the current conventional method based on the superposition principle can not take this kind of load coupling into account, and there are still many problems to be solved. Therefore, the theoretical analysis and laboratory model test of horizontal loaded pile, torsional pile and H-T bearing pile are carried out in this paper. The main work is as follows: firstly, it is assumed that the soil around the pile satisfies the distribution characteristics of generalized Gibson foundation. Based on the theory of virtual soil pile, the energy governing equation of pile-soil system is obtained based on energy method, and the control equations of pile body and pile-side soil under horizontal load are established by variational principle, respectively. Then the center point difference method is used to derive the pile-soil response value. On this basis, it is assumed that the plastic zone of the pile-side soil extends from the ground to the bottom, and the pile-soil response value is obtained when the pile-side soil is in plastic state. Secondly, based on the shear displacement method and equilibrium principle, considering the distribution of shear modulus along the depth of the pile, it is assumed that the plastic deformation of the soil on the side of the pile gradually develops from top to bottom with the increase of pile top load. The analytical solution of the internal force deformation of the pile is obtained when the pile side soil is in elastic, elastic-plastic and plastic state under pure torque. At the same time, according to the delamination characteristic of foundation soil in engineering, an elastic-plastic torsional load transfer model is introduced, and the calculation formula of torque-torsion angle of pure torsional pile in layered foundation is given. Thirdly, based on the m method and the improved finite member element method, the coupling relation of horizontal force H and torque T is taken into account in the stiffness matrix of the bar element, and the unified stiffness equation of the bar element is obtained. Considering the different boundary conditions, the displacement solutions of the internal force of the pile body under the combined action of H-T are obtained. Finally, a self-made sand box and pulley loading device was used to complete the laboratory model test of a single pile in sand under the combined action of pure horizontal force H, torque T and H-T. The corresponding load-deformation curve on the top of the pile and the load-displacement curve of the pile body were obtained.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU473.1

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