边载作用下桥梁被动基桩工作机理与实例分析

发布时间：2018-05-15 10:31

本文选题：被动桩 + 边载作用　；参考：《东南大学》2015年硕士论文

【摘要】：非对称荷载是桥梁桩基工程中常见的工况,如单侧堆载或大开挖等,当地表下存在流塑性软土层时,非对称荷载容易导致软土侧向流动,对基桩产生附加的侧向土压力,影响上部结构的稳定性,因此对此类桩(即被动桩)的工作机理的研究尤为重要。由于被动桩的受力性状复杂,目前国内外尚无统一的、精确度高的分析模型,较常见的被动桩分析方法有悬臂桩法、地基梁法等,无一例外均对桩土相互作用关系做了简化,而简化的方式和模型直接决定了计算结果的可靠度。本文采用的是分段耦合的分析方法,将被动桩按其受力性状分为上部自由段、流塑土层被动段以及主动段三部分分别建立数学模型,得到的解答根据分界面连续性原理采用矩阵相乘的方法进行耦合,得到桩身的内力位移解答。将计算过程编写了Fortran程序,并对锡张高速和南京某桥梁两个工程案例做了计算分析验证。本文完成的主要工作如下：(1)基于被动桩的实际受力性状,推导了梁和地基梁在不同工况时的内力位移解答,其中地基梁根据轴力的不同假设分别给出了轴力不变时的解析解答和考虑轴力变化时的幂级数解答。(2)根据不同工况,采用两套方法对被动桩进行解答。当考虑土体分层时,被动段和主动段按土层分段,各段均采用地基抗力常系数模型的解析解法；当考虑主动段土体屈服时,采用“m”法幂级数解答。(3)给出了桩台基础及各类边界条件下桥梁桩基的内力解答。(4)基于两个典型的桥梁被动桩失稳工程案例,利用本文所述的方法进行计算验证,得到的结果与实测数据吻合较好。
[Abstract]:Asymmetric load is a common condition in bridge pile foundation engineering, such as unilateral heaped load or large excavation. When there is fluid-plastic soft soil layer under the local surface, asymmetric load can easily lead to lateral flow of soft soil and generate additional lateral earth pressure on foundation pile. The stability of superstructure is affected, so it is very important to study the working mechanism of this kind of pile (passive pile). Because of the complex mechanical behavior of passive pile, there is no unified and accurate analysis model at home and abroad. The common methods of passive pile analysis are cantilever pile method, foundation beam method, etc., without exception, the pile-soil interaction relationship is simplified. The simplified method and model directly determine the reliability of the calculation results. In this paper, a piecewise coupling analysis method is used to divide the passive pile into three parts: the upper free section, the passive section of the fluid-plastic soil layer and the active section according to its mechanical properties. The solution is coupled by matrix multiplication according to the principle of interface continuity, and the solution of internal force displacement of pile body is obtained. The Fortran program is written, and the two engineering cases of tin Zhang high speed and Nanjing bridge are analyzed and verified. The main work accomplished in this paper is as follows: (1) based on the actual mechanical behavior of the passive pile, the solutions of the internal force displacement of the beam and the foundation beam under different working conditions are derived. According to the different assumptions of axial force, the foundation beam gives the analytical solution for the invariant axial force and the power series solution for considering the variation of the axial force. (2) according to different working conditions, two sets of methods are used to solve the passive pile. When delamination of soil is considered, the passive and active segments are divided according to the soil layer, and the analytical solution of the constant coefficient model of soil resistance is adopted in each segment, and when the active section of the soil is considered to yield, The solution of internal force of pile foundation and bridge pile foundation under all kinds of boundary conditions is given by using "m" method power series solution. (4) based on two typical examples of bridge passive pile instability engineering, the method described in this paper is used to verify the calculation. The results are in good agreement with the measured data.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U443.15

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