河道冲刷对既有桥梁单桩基础竖向承载性状影响的数值分析

发布时间：2018-04-23 19:45

本文选题：冲刷 + 单桩基础　；参考：《天津大学》2014年硕士论文

【摘要】：冲刷是由运动水流引起的桥梁基础周围土体受侵蚀的过程,其后果轻则降低基础承载力,重则导致整座桥梁结构损毁。尽管冲刷引起的桥梁破坏促使人们研究冲刷过程并预测桥墩处的最大冲刷深度,但涉及如何评价冲刷对桩基竖向承载性状影响的研究尚屈指可数。因此,本文旨在研究冲刷后桩基础竖向承载特性的变化规律。本文利用ABAQUS有限元分析软件,引入模拟开挖的思想,将土体冲刷过程看作开挖土体的过程进行模拟计算,分析了高、低承台单桩基础遭受冲刷过程中竖向承载性状的变化。主要研究工作如下:1.现有研究中,往往通过移除冲刷深度范围内的整个土层来考虑冲刷对竖向受荷桩承载性状的影响。本文研究工作中不仅考虑了冲刷坑的深度因素,还考虑了宽度和坡度因素。基于参数敏感性分析来研究冲刷坑尺寸因素的影响,结果表明,与冲刷坑宽度和坡度相比,冲刷深度是影响桩基竖向承载特性的最主要因素。2.为了更深入地探讨冲刷对砂土中桩竖向承载性状的影响,研究了土体单元刚度、桩长细比等因素对受冲刷单桩基础竖向承载力下降百分比(PDV)的影响规律。研究结果表明,受冲刷后松软砂土中桩的PDV值比密实砂土中的高;当冲刷深度水平Sd/D=8时,松软砂土中桩的竖向极限承载力折减近一半。冲刷后短桩的竖向极限承载力损失程度更大、桩基础更容易失效。增大桩径有利于减缓桩基由冲刷导致的竖向承载力降低的趋势,但效果不明显。3.探讨了不同冲刷深度条件下桩侧摩阻力以及桩身轴力等的变化规律。通过上述研究,取得了冲刷对桩基竖向承载特性影响的基本认识,为评估遭受水流冲刷的整座桥梁的安全性奠定了基础,所得成果对于改进桥梁桩基础设计理论有一定的参考意义。
[Abstract]:Scouring is a process of soil erosion around the bridge foundation caused by moving water, which reduces the bearing capacity of the foundation and damages the whole bridge structure. Although the damage of bridges caused by scour impels people to study the scour process and predict the maximum scour depth at the pier, there are few studies on how to evaluate the influence of scour on the vertical bearing behavior of pile foundation. Therefore, this paper aims to study the variation of vertical bearing characteristics of pile foundation after erosion. In this paper, ABAQUS finite element analysis software is used to analyze the vertical bearing behavior of single pile foundation with high and low caps during erosion by introducing the idea of simulated excavation. The scouring process of soil is regarded as the process of soil excavation. The main research work is as follows: 1. In the present research, the effect of scour on the bearing behavior of vertical loaded piles is often considered by removing the whole soil layer within the range of scouring depth. In this paper, not only the depth of the scour pit is considered, but also the width and slope are considered. Based on the parameter sensitivity analysis, the influence of the scour pit size is studied. The results show that the scour depth is the most important factor affecting the vertical bearing characteristics of pile foundation compared with the width and slope of the scour pit. In order to investigate the effect of erosion on vertical bearing behavior of piles in sand, the effects of soil element stiffness and ratio of pile length to slenderness on the decreasing percentage of vertical bearing capacity (PDV) of single pile foundation subjected to erosion were studied. The results show that the PDV value of piles in soft sand after scouring is higher than that in dense sand, and the vertical ultimate bearing capacity of piles in soft sand is reduced by nearly half when the depth of erosion is SD / D = 8. The loss of vertical ultimate bearing capacity of short piles after scouring is greater, and the pile foundation is more prone to failure. Increasing pile diameter is helpful to reduce the vertical bearing capacity of pile foundation caused by erosion, but the effect is not obvious. The variation law of lateral friction and axial force of pile under different scour depth is discussed. Through the above research, the basic understanding of the impact of scour on the vertical bearing characteristics of pile foundation is obtained, which lays a foundation for evaluating the safety of the whole bridge subjected to water erosion. The obtained results have certain reference significance for improving the design theory of bridge pile foundation.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U443.15

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