竖向荷载作用下GRF桩基础承载特性数值模拟研究

发布时间：2018-07-17 03:11

【摘要】：GRF（Geo-Reinforement type Foundation）桩基础是一种新型岩土增强型基础，它在超大直径桩周围分层、辐射状分布锚杆来改善桩-土相互作用机理。该种桩基础具有施工工艺简单、承载力大、沉降小、节约成本、经济效益和社会效益高等明显优点，特别适用于一桩一柱的大型基础，具有广阔的应用前景。为了阐明GRF桩基础在竖直荷载作用下的承载机理，本文利用岩土计算软件FLAC3D，建立三维非线性模型，考虑桩-土、锚杆-土的接触效应，分析研究了桩侧土体、锚杆及桩端土体变形机制，以及锚杆长度、锚杆数量、锚杆间距和锚杆排数对GRF桩基础承载力和桩土变形特性的影响，取得了如下成果： 1GRF桩基础具有承载力大、沉降小等特点，这是因为锚杆的存在使得GRF桩基础表现出与普通等直径直桩不同的承载特性，锚杆伸入土中，在上部竖直荷载作用下，随桩体向下位移，受到土体对它的向上的反作用力，构成桩体承载力的重要组成部分。 2随着荷载的增大，锚杆作用发挥程度增加；锚杆发挥作用程度越大，GRF桩基础桩侧土体变形相对于等直径直桩桩侧土体变形越小，而且锚杆作用的发挥改变了GRF桩基础桩侧土体的受力变形特性。锚杆长度范围内的土体变形由原来的剪切变形转化为剪切、压缩组合变形。 3由于锚杆的存在，，GRF桩基础桩周土体变形明显小于等直径直桩的桩周土体变形，且桩侧土体变形表现出了不同的趋势。锚杆受到下部土体的反作用力而发生变形，锚杆的变形随着荷载的增大而增大，且在相同荷载作用下不同埋置深度锚杆变形也不同。 4计算结果表明，GRF桩基础的承载力随着锚杆长度的增加而增加，增加锚杆数量可使GRF桩基础承载力明显提高，在锚杆总数不变的情况下增加锚杆的排数或增大锚杆间距可使GRF桩基础承载力得到一定程度的提高。
[Abstract]:GRF (Geo-Reinment type Foundation) pile foundation is a new type of geo-soil enhanced foundation, which delaminate around super-diameter piles and radially distributes anchors to improve the pile-soil interaction mechanism. This kind of pile foundation has the advantages of simple construction technology, large bearing capacity, small settlement, saving cost, high economic benefit and social benefit. It is especially suitable for large foundation with one pile and one column, and has broad application prospect. In order to elucidate the bearing mechanism of GRF pile foundation under vertical load, a three-dimensional nonlinear model is established by using the geotechnical calculation software FLAC3D. considering the pile-soil contact effect, the pile-side soil mass is analyzed and studied. The deformation mechanism of anchor and pile end soil, and the influence of length of anchor rod, number of anchors, spacing of anchor rod and number of anchor bars on bearing capacity and deformation characteristics of GRF pile foundation have been obtained as follows: (1) the bearing capacity of GRF pile foundation is large, the bearing capacity of GRF pile foundation is large, and the bearing capacity of GRF pile foundation is large. This is because the existence of anchor rod makes the foundation of GRF pile show different bearing characteristics from that of ordinary straight pile with equal diameter. The anchor rod extends into the soil and displacements with the pile body under the action of vertical load in the upper part. By the soil upward reaction force, constitute an important part of the bearing capacity of the pile. 2 with the increase of load, the role of anchor increased; The larger the acting degree of anchor is, the smaller the deformation of soil around GRF pile foundation is compared with that of equal diameter straight pile side soil, and the effect of anchor rod on the deformation characteristics of pile side soil of GRF pile foundation is changed. The deformation of soil in the range of anchor length is changed from original shear deformation to shear deformation and compression combined deformation. 3 because of the existence of anchor rod, the deformation of soil around the pile of GRF pile foundation is obviously smaller than that of the soil around the pile with equal diameter vertical pile. The deformation of the soil around the pile shows different trends. The anchor rod is deformed by the reaction force of the lower soil, and the deformation of the anchor rod increases with the increase of the load. The calculated results show that the bearing capacity of GRF pile foundation increases with the increase of anchor length, and the bearing capacity of GRF pile foundation can be obviously increased by increasing the number of anchors. The bearing capacity of GRF pile foundation can be improved to a certain extent by increasing the number of anchors or increasing the spacing of anchors when the total number of anchors is constant.
【学位授予单位】：长江科学院
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU473.1

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