桩土界面特征对非挤土桩承载性状的影响分析

发布时间：2018-01-14 11:23

本文关键词：桩土界面特征对非挤土桩承载性状的影响分析　出处：《郑州大学》2014年硕士论文　论文类型：学位论文

【摘要】：在高层建筑、桥梁、市政和港口等深基础工程中，常用的、最为经济的桩型之一是非挤土桩，如钻孔灌注桩。对于其他条件相同但成孔方式不同的钻孔灌注桩，其承载能力往往差异较大。其根本原因在于因钻孔方式不同导致桩土界面的接触特征相差较大。桩土界面特征，本文是指桩土接触界面的相对刚度、相对粗糙度、桩土接触面附近土的变形特征、桩周接触面附近土体剪切受荷后剪切带的形成、发展及表现出的剪胀、剪缩特性，以及桩径和土的初始应力水平等。本文主要针对砂土的剪切变形特征，尤其是处于临界状态时所表现出的剪胀或剪缩特性，在以往学者对土-结构面接触特性试验和本构模型研究的基础上，归纳、计算（应用所编制的计算程序）和分析了土-结构面接触特性对剪切变形的影响规律，并与其他文献的计算结果进行比较，验证了数值方法的正确性。该接触面剪切模型是一种薄层临界状态模型，薄层厚度即为剪切带宽度。然后将该接触面模型应用到非挤土桩中。在对传统的桩基承载计算的传递函数法进行修正的基础上，运用所编制的桩基修正的传递函数法计算程序，分析了考虑桩土界面接触特性对单桩承载性状的影响，，揭示侧摩阻力的发挥与桩土相对位移的关系。使得桩基的承载和沉降计算能够考虑更多的实际因素，分析更接近于实际情况，从而使桩基承载性状的研究更趋于合理。主要研究成果如下：（1）本文采用的界面剪切模型虽然模型参数较多，但能够很好地描述土-结构界面的剪切特性，且能够较好地用于桩基承载性能的研究。（2）采用CNL和CNS两种数值试验，分析影响土-结构界面剪切特性的相关参数，得到：砂土的初始孔隙比越小、围压越小、接触面厚度越薄、法向刚度越小，剪切时的剪胀性越明显、剪缩性越弱、达到相变状态需要的体应变也越小；对于密砂而言，接触面越相对粗糙，峰值剪应力强度越大，应变软化现象越明显，而对于相对光滑接触面，砂土呈现的剪缩特性较强，其应变软化现象不明显。（3）桩土接触面越相对粗糙、桩周土体越密实，单桩的竖向承载力越大，桩的侧摩阻力沿深度分布所呈现的非线性越明显且峰值越大，同时桩侧摩阻力的发挥需要更大的桩土相对位移。（4）桩周土体因接触面相对粗糙度的不同，剪切时出现剪缩或先剪缩后剪胀现象，应力应变关系呈现出软化或硬化特性。
[Abstract]:In high-rise buildings, bridges, ports and other municipal and commonly used in deep foundation engineering, pile type, one of the most economical non compaction pile, bored pile. As for the other conditions are the same but different hole bored pile, the bearing capacity is often quite different. The main reason for drilling different ways lead to the contact characteristics between the pile and the soil is larger. The characteristics of pile-soil interface, this paper refers to the soil pile interface relative stiffness, relative roughness, deformation characteristics of pile soil contact surface of the soil near the pile near the contact surface, week of shear loading after the formation of shear bands, and showed the development of shear dilatancy, shear contraction, and the diameter of the pile and the soil initial stress level.
In this paper, the sand shear deformation characteristics, especially in the critical state exhibit dilatancy or shear contraction, in previous studies on soil structure contact based characteristic test and constitutive model research, induction, calculation (program application compiled) and analysis of the soil structure surface contact characteristics influence of shear deformation, and the calculation results were compared with other literatures, to verify the correctness of the numerical method. The shear model is a thin layer of critical state model, the thickness of the thin is the width of the shear band. Then the contact model is applied to non compaction pile in pile foundation. The traditional calculation of load transfer function method is modified on the basis of using pile foundation compiled by modified method of transfer function calculation program, considering the contact characteristics of pile-soil interface effect on bearing capacity of single pile, revealing the side The relationship between frictional resistance and relative displacement of pile and soil makes the calculation and calculation of pile foundation bearing more practical factors. The analysis is more close to the actual situation, so that the study of pile bearing behavior is more reasonable.
The main research results are as follows:
(1) the interface shear model adopted in this paper has many model parameters, but it can well describe the shear properties of soil structure interface, and it can be applied to the research of pile foundation bearing capacity better.
(2) using CNL and CNS two kinds of numerical experiments, analysis the influence of the soil structure interface shear properties of the relevant parameters, are: the initial pore sand ratio is smaller, the smaller the pressure, the contact surface of the thin thickness, normal stiffness decreases, shear dilatancy and shear shrinkage is more obvious. The weaker to body strain phase transition also takes less; for dense sand, the contact surface is relatively rough, the peak shear stress intensity, strain softening phenomenon is more obvious, while the relatively smooth surface, strong sand presents shear contraction, the strain softening phenomenon is not obvious.
(3) the more rough the pile soil contact surface is, the more dense the soil around the pile is, and the larger the vertical bearing capacity of a single pile is. The larger the pile side friction is, the larger the larger the peak value is. The bigger the pile side friction is, the greater the relative displacement of pile and soil will be.
(4) due to the different roughness of the contact surface, shear stress or shear dilatation first appeared in the soil around the pile, and the relationship between stress and strain showed softening or hardening characteristics.

【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU473.1

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