考虑初应力时饱和土中周期排桩减振特性研究

发布时间：2018-11-14 14:42

【摘要】：周期结构对频率处于衰减域范围内的弹性波的传播具有抑制作用,因此,基于这一理论提出的周期排桩能作为一种隔离环境振动的措施。现有的利用周期理论对排桩结构的研究,主要存在如下局限:一是大多将土体假设为单相均质土,未采用多相介质模型;二是未考虑排桩结构中初应力的影响。而实际工程中由于存在地下水,土体更加接近饱和土;另外,工程中在桩的贯入、土的再固结过程中均会产生初应力,因此,有必要考虑初应力的影响。因此,本文将基于周期结构理论和饱和多孔介质的Biot理论,研究考虑初应力时饱和土中周期排桩的减振特性。论文主要内容包括:1.介绍了周期结构基本理论和饱和土的Biot理论,介绍了计算衰减域的有限单元法。2.首先验证了利用有限单元法计算饱和土中周期排桩形成的衰减域的正确性,其次在考虑初应力的情况下计算了饱和土中周期排桩形成的衰减域,在此基础上进一步讨论了相关参数对衰减域的影响。3.建立了考虑和不考虑初应力的二维频响分析模型,验证了利用排桩结构进行环境减振的可行性,揭示了初应力对频率响应的影响机理。4.建立了考虑和不考虑初应力的三维频响分析模型,结果表明随着桩长度的增加,衰减域内的衰减效果逐渐明显并且三维模型的计算结果逐渐收敛于二维模型的计算结果。此外,当桩长不是特别长时,初应力值可以近似取为桩顶部的应力值。
[Abstract]:The periodic structure can restrain the propagation of elastic wave in the range of frequency attenuation. Therefore, the periodic pile row based on this theory can be used as a measure to isolate the vibration in the environment. The main limitations of the existing research on pile row structure by using periodic theory are as follows: first, most of the soil is assumed as single-phase homogeneous soil without multiphase medium model; second, the influence of initial stress in pile row structure is not considered. Due to the existence of groundwater, the soil is closer to saturated soil in practical engineering, and in addition, the initial stress will be produced in the process of soil reconsolidation in the process of pile penetration, so it is necessary to consider the effect of initial stress. Therefore, based on the periodic structure theory and the Biot theory of saturated porous media, the damping characteristics of periodic piles in saturated soil under initial stress are studied in this paper. The main contents of this paper are as follows: 1. The basic theory of periodic structure and the Biot theory of saturated soil are introduced, and the finite element method for calculating attenuation domain is introduced. 2. Firstly, the validity of the finite element method for calculating the attenuation region of periodic piles in saturated soil is verified. Secondly, the attenuation region of periodic pile row formation in saturated soil is calculated considering the initial stress. On the basis of this, the influence of the related parameters on the attenuation region is further discussed. 3. 3. A two-dimensional frequency response analysis model considering and disregarding the initial stress is established, which verifies the feasibility of using the pile row structure to reduce the ambient vibration, and reveals the mechanism of the influence of the initial stress on the frequency response. 4. A three-dimensional frequency response analysis model with and without initial stress is established. The results show that the attenuation effect in the attenuation domain becomes more and more obvious with the increase of pile length, and the calculated results of the three-dimensional model converge to that of the two-dimensional model. In addition, when the pile length is not very long, the initial stress value can be approximately taken as the stress value at the top of the pile.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU435

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