有桩周土侧向位移的倾斜桩竖向承载性能研究

发布时间：2018-05-01 02:12

本文选题：倾斜桩 + 倾斜率　；参考：《山东建筑大学》2017年硕士论文

【摘要】：随着城市化进程的加剧,桩偏斜事故出现频率有上升趋势。特别是近年来,基坑开挖、堆载、路堤荷载等原因产生的倾斜桩日益增多,这类桩常常伴有土体的水平向变形,即桩周土侧向位移。到目前为止,对倾斜桩承载机理的研究还不深入,特别是对有桩周土侧向位移倾斜桩的承载机理还处于空白阶段,工程实践中对有桩周土侧向位移的倾斜桩加固常借用竖直桩的加固方法,这显然不能合理反映倾斜桩的实际工作性状,导致倾斜桩加固或设计保守,浪费严重;或重视不够,补救方法不当,埋下工程隐患。因此,通过对倾斜桩和竖直桩在竖向承载性能和荷载传递规律的差别开展研究,进而为倾斜桩加固提供技术支持,减少由于加固方案保守而造成资源浪费、或消除由于加固措施不到位而留下安全隐患,具有非常重要的实际意义。本文首先通过模型实验研究了竖向荷载作用下无桩周土侧向位移和有桩周土侧向位移的三种倾斜率桩的竖向承载变形性状,并与相应竖直桩进行了对比。可以得出,对于粉土土质条件的桩身整体倾斜的桩,当桩身倾斜率小于2%时,相同情况下,倾斜桩的桩顶竖向位移和端阻比基本不变;当倾斜率大于4%时,倾斜桩竖向沉降和端阻比不再是判定其承载力的决定因素,水平位移逐渐成为关键因素。倾斜桩在极限荷载作用下桩倾斜一侧和背离一侧最大弯矩的桩身位置与桩倾斜率无关,且随着桩倾斜率的增大,桩身最大弯矩的绝对值逐渐增大。在模型试验的基础上,采用有限元分析重点研究了桩周土侧向位移大小、桩周土侧向位移作用范围对倾斜桩竖向承载变形性状及荷载传递机理的影响,并与相应竖直桩进行了对比。可以得出,对于粉土土质条件和桩身整体倾斜的桩,随着桩周土侧向位移大小和竖向作用范围的逐渐增大,桩顶竖向位移和水平位移逐渐增大。倾斜桩土压力递减较快范围与桩倾斜率无关,土压力递减较快范围为桩倾斜一侧5d和桩背离一侧5d。当倾斜率小于2%时,桩侧摩阻力沿桩身分布情况类似于竖直桩;当倾斜率大于2%时,桩顶以下0~7d范围内,随着倾斜率的增大,相同位置处桩侧平均摩阻力逐渐增大;桩顶以下7d~40d范围内,随着倾斜率的增大,相同位置处桩侧平均摩阻力基本不变。
[Abstract]:With the development of urbanization, the frequency of pile skew accidents is increasing. Especially in recent years, the inclined piles caused by excavation, surcharge and embankment load are increasing day by day. These piles are often accompanied by horizontal deformation of soil, that is, lateral displacement of soil around piles. Up to now, the research on bearing mechanism of inclined pile is not deep, especially the bearing mechanism of inclined pile with lateral displacement of soil around piles is still in blank stage. In engineering practice, the vertical pile is often used to reinforce the inclined pile with lateral displacement of soil around the pile, which obviously can not reflect the actual working behavior of the inclined pile, which leads to the reinforcement of the inclined pile or the conservative design of the pile, which is wasteful, or is not paid enough attention to. The remedy method is improper and the hidden trouble of the project is buried. Therefore, through the research on the difference between inclined pile and vertical pile in vertical bearing capacity and load transfer law, it can provide technical support for the reinforcement of inclined pile and reduce the waste of resources caused by conservative reinforcement scheme. It is of great practical significance to eliminate the hidden danger caused by the lack of reinforcement measures. In this paper, the behavior of vertical bearing deformation of three kinds of inclined pile with lateral displacement of soil around the pile and the lateral displacement of the soil around the pile under vertical load is studied by model experiment, and compared with the corresponding vertical pile. It can be concluded that for the pile with silty soil condition, when the slope ratio of pile body is less than 2, the vertical displacement of the pile top and the ratio of end resistance to resistance of the inclined pile are basically unchanged under the same condition, and when the slope ratio is greater than 4, Vertical settlement and end-resistance ratio of inclined pile are no longer the decisive factors to determine its bearing capacity, but horizontal displacement is becoming the key factor. The position of the maximum bending moment of the inclined pile under the ultimate load is independent of the slope ratio of the pile, and the absolute value of the maximum moment increases with the increase of the slope ratio of the pile. On the basis of model test, the effects of lateral displacement of soil around pile and the range of lateral displacement of soil around pile on vertical bearing deformation behavior and load transfer mechanism of inclined pile are studied by finite element analysis. The results are compared with the corresponding vertical piles. It can be concluded that the vertical displacement and horizontal displacement of the top of the pile increase with the increase of the lateral displacement and the vertical action range of the soil around the pile for the silty soil condition and the whole inclined pile body. The rapid decline range of soil pressure of inclined pile has nothing to do with the slope ratio of pile. The quick range of soil pressure decline is 5 days on the inclined side of the pile and 5 days on the deviating side of the pile. When the slope ratio is less than 2, the frictional resistance distribution along the pile body is similar to that of the vertical pile, and when the slope ratio is greater than 2, the average frictional resistance of the pile side increases gradually with the increase of the slope ratio in the range of 0 ~ 7 days below the top of the pile. In the range of 7d~40d below the top of the pile, with the increase of the slope ratio, the average frictional resistance of the pile side at the same position is basically unchanged.
【学位授予单位】：山东建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU473.1

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