单桩—土—承台相互作用的DEM数值模拟

发布时间：2018-10-25 09:51

【摘要】：桩基础作为工程实践中的基础部分以其具有的承载能力大、稳定性好、沉降量小等特点受到高度重视。桩基础的稳定会影响到整个工程的质量。然而由于土体之间的性质存在着较大的差异和桩基础的设计理念不同,使得桩基础与土体之间的相互作用变得尤为复杂。桩-土-承台之间的相互作用仍有诸多地方需要完善。桩-土-承台相互作用的数值模拟分析中较多基于连续介质力学研究方法。然而土体作为一种离散不连续介质,采用基于连续假设的分析理论弱化了土体本身所具有的颗粒离散属性。土体颗粒之间不存在严格意义上的变形协调,相邻两个土体颗粒之间的运动存在一定的差异。而离散元分析方法符合土体的这些属性。但是当针对结构大,颗粒需要细分的情况,离散单元法的不足之处也表现的非常明显。面对较多的颗粒时程序无法高效地完成计算。采用耦合的方法将离散元与其他数值方法结合起来,可以发挥各自的优势,提高计算效率,扩展离散元法的应用范围。本文主要的研究内容如下：(1)简述了桩基础的作用、设计理念和常用的理论、试验、数值模拟分析方法,同时对离散元在桩基础工程中的应用和离散-连续耦合方法的发展状况做了简单的概述。(2)对离散元及分析软件PFC3D的工作原理、基本假设、分析方法等与本文相关的方面做了简单的介绍。(3)采用离散元分析软件建立不同承台尺寸、桩截面边长、桩长的桩基础模型和不同摩擦系数、孔隙度的土体模型,分别探讨不同的桩基础模型和土体性质的改变对桩-土-承台之间相互作用的影响。对模型施加竖向荷载,控制沉降速度,分析桩基础在沉降过程中的桩端阻力、桩侧摩阻力、承台阻力和施加总荷载的变化规律,研究荷载在土体颗粒之间的传递特点,土体颗粒的运动特点,土体应力及孔隙度的变化规律。(4)采用离散-连续耦合的方法研究桩基础的受载沉降过程。
[Abstract]:As the foundation part of engineering practice, pile foundation has been attached great importance for its great bearing capacity, good stability and small settlement. The stability of pile foundation will affect the quality of the whole project. However, the interaction between pile foundation and soil is especially complicated because of the great difference of soil properties and the different design concept of pile foundation. The interaction between pile-soil-cap still needs to be improved. The numerical simulation of pile-soil-cap interaction is based on continuum mechanics. However, as a discrete discontinuous medium, the analysis theory based on continuous hypothesis weakens the discrete properties of soil particles. There is no strict deformation coordination between soil particles, and there are some differences in motion between adjacent soil particles. The discrete element analysis method accords with these properties of soil. But when the structure is large and the particles need to be subdivided, the shortcomings of the discrete element method are obvious. In the face of more particles, the program can not complete the calculation efficiently. Using the coupling method to combine the discrete element with other numerical methods can give play to their respective advantages, improve the calculation efficiency and expand the application scope of the discrete element method. The main contents of this paper are as follows: (1) the function of pile foundation, the design concept and the commonly used theories, tests, numerical simulation and analysis methods are briefly described. At the same time, the application of discrete element in pile foundation engineering and the development of discrete-time continuous coupling method are briefly summarized. (2) the working principle of discrete element and the analysis software PFC3D, the basic assumptions, are given. The analysis methods and other related aspects are briefly introduced. (3) the discrete element analysis software is used to establish the pile foundation model with different pile cap size, pile cross-section side length, pile length and soil model with different friction coefficient and porosity. The effects of different pile foundation models and soil properties on the pile-soil-cap interaction are discussed. The vertical load is applied to the model, the settlement velocity is controlled, and the variation law of pile tip resistance, pile side friction resistance, pile cap resistance and total load applied in the settlement process of pile foundation are analyzed, and the characteristics of load transfer between soil particles are studied. The movement characteristics of soil particles, the variation law of soil stress and porosity. (4) the discrete continuous coupling method is used to study the settlement process of pile foundation under load.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU470

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