螺旋钢桩冻胀融沉特性试验研究

发布时间：2018-04-11 07:02

本文选题：螺旋钢桩 + 冻胀融沉　；参考：《北京交通大学》2017年硕士论文

【摘要】：建(构)筑物基础的冻胀融沉破坏一直是寒区工程所面临的主要问题,其严重影响着上部结构的稳定性。螺旋桩是一种拥有良好抗拔承载力和整体稳定性的新型桩基础,在非冻土地区抗拔工程中已经得到验证。近些年发展起来的寒区光伏发电工程,已经开始使用螺旋钢桩作为光伏电池板的支架基础。目前国内外关于螺旋桩的冻胀融沉特性研究相对缺乏,研究成果尚不成熟,因而针对光伏支架螺旋钢桩的冻胀融沉特性加以研究,不但对光伏发电工程具有重要意义,也对寒区工程桩基选型具有重要指导意义。本文采用室内模型试验的方法对桩型参数不同的螺旋钢桩进行冻胀融沉特性研究,主要研究内容包括:1)以传统桩基冻拔受力分析和非冻土环境下螺旋钢桩抗拔承载力分析为基础,提出螺旋钢桩在桩周土冻胀过程中桩身受力特点,分析了冻深范围内螺旋叶片对于冻拔力大小所产生的影响,并针对半螺旋桩提出一种桩顶冻胀力的简单计算模型。2)通过基础试验测定了填土的各项物理指标,为冻胀融沉试验提供了基础。通过试验结果可判断所选土样为粉土,属强冻胀土。3)在桩顶无约束的情况下,对不同型号的螺旋钢桩进行一维冻胀试验和融沉试验,分析了试验过程中箱内土体温度场变化规律、桩身冻拔位移量发展规律以及融化阶段桩体沉降规律,并拟合得到冻拔位移量Δh和冻结深度Hf的多项式方程。对比试验结果可得到,在冻土层内布置螺旋叶片会大大增加桩体冻拔位移量,减小未冻土层范围内的螺旋钢桩螺距并增大螺旋叶片直径均会提高桩体的冻胀融沉稳定性。4)在限制桩顶冻拔位移的情况下,对不同型号的螺旋钢桩进行一维冻胀试验和融沉试验,分析了试验过程中桩顶冻胀力的发展规律,并拟合得到桩顶冻胀力N和冻结深度Hf的指数方程。对比试验结果可得到,在冻土层内布置螺旋叶片会大大增加桩顶冻胀力,减小未冻土层范围内的螺旋钢桩螺距并增大螺旋叶片直径对减小桩顶冻胀力有一定作用,但效果不明显。
[Abstract]:The frost heaving and thawing collapse of the building foundation is always the main problem in the cold region engineering, which seriously affects the stability of the superstructure.Spiral pile is a new type of pile foundation with good uplift bearing capacity and overall stability, which has been verified in non-frozen soil area.In recent years, helical steel piles have been used as the support foundation of photovoltaic panels in cold area photovoltaic power generation projects.At present, the research on frost heaving and thawing settlement characteristics of spiral piles at home and abroad is relatively lacking, and the research results are still immature. Therefore, it is not only of great significance to photovoltaic power generation engineering to study the characteristics of frost heave thawing settlement of helical steel piles with photovoltaic support.It is also of great significance to the selection of pile foundation in cold region.In this paper, the frost heaving and thawing settlement characteristics of helical steel piles with different pile parameters are studied by using indoor model test.The main research contents include: (1) based on the traditional analysis of freezing and drawing force of pile foundation and the analysis of uplift bearing capacity of spiral steel pile under non-frozen soil environment, the characteristics of pile body bearing capacity during frost heaving process of spiral steel pile are put forward.This paper analyzes the influence of helical blade on the freezing drawing force in the range of freezing depth, and puts forward a simple calculation model of frost heave force at the top of the pile for semi-helical pile.It provides a basis for frost heaving and thawing test.Through the test results, it can be judged that the selected soil sample is silt, which belongs to strong frost heaving soil .3) under the condition that the pile top is unconstrained, the one-dimensional frost heave test and thawing test are carried out on different types of spiral steel piles.The variation law of temperature field in box soil mass, the development law of frozen drawing displacement of pile body and the settlement law of pile body in melting stage are analyzed, and the polynomial equations of displacement 螖 h and freezing depth HF are obtained.By comparing the test results, it is found that the placement of helical blades in the frozen soil will greatly increase the displacement of the pile during freezing and drawing.Reducing the pitch of spiral steel pile and increasing the diameter of helical blade in unfrozen soil can improve the stability of frost heave thawing settlement of pile. 4) under the condition of limiting the displacement of pile top freezing and drawing,The one-dimensional frost heave test and thawing test for different types of spiral steel piles are carried out. The development law of the pile top frost heave force is analyzed and the exponential equations of the pile top frost heave force N and freezing depth HF are obtained.By comparing the test results, it is found that the placement of helical blades in frozen soil will greatly increase the frost heaving force of the pile top, reduce the pitch of the spiral steel pile and increase the diameter of the helical blade in the unfrozen soil layer, which will play a certain role in reducing the frost heave force of the pile top.But the effect is not obvious.
【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】：TU473.1

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