考虑侧阻增强效应的基桩极限承载力试验及确定方法研究

发布时间：2018-09-07 09:54

【摘要】：桩基础是应用最广泛的基础形式之一,其种类和形式多样,主要功能为承受上部荷载并将竖向荷载传递至深层地基,因此极限竖向承载力的研究是桩基础设计计算最为核心的内容之一。目前,现行各规范均认为基桩侧摩阻力与桩端阻力是相互独立、互不联系的两个部分,即基桩极限承载力为侧阻力与端阻力之和。然而从一些现场试验资料及室内模型试验可发现:桩侧摩阻力与桩端阻力并非完全独立,二者在桩基加载过程中存在某种程度的相互作用,且这种相互作用将使侧阻值明显增强,进而对基桩竖向承载力计算有较大影响。因此本文试图对侧阻增强效应开展室内模拟实验,借助基桩静载试验观测侧阻增强效应对基桩侧摩阻力的影响,并探究桩径对这一效应的作用规律,在此基础上引进极限分析法,模拟桩基承载过程中桩端阻力与桩侧阻力的相互作用,提出可考虑基桩侧阻增强效应的极限桩基础竖向承载力计算公式,对优化基桩设计、进一步挖掘桩基承载潜能起到一定借鉴作用。本文首先根据室内模型试验,在基桩加载过程中对基桩端部一定范围内侧阻变化规律进行监测,验证侧阻增强效应的存在,并基于不同桩径的对比试验,探讨了桩径对基桩侧阻增强效应的影响,结果表明随桩径增大,侧阻增强效应越明显。然后在室内模拟实验研究的基础上,考虑基桩底部桩土的相对位移量、桩土接触面的性质、桩端持力层的强度、桩端阻的发挥程度、土体复杂性等因素的影响,对基桩侧阻增强效应及过程进行模拟,并基于-深基础破坏模式,引进极限分析上限法,推算出考虑侧阻增强效应的基桩竖向承载力公式,并对基桩竖向承载力的各影响因素进行敏感性分析,探求其各因素对侧阻增强效应的影响规律。最后引用现场基桩静载实例数据,基于本文改进的基桩竖向极限承载力公式,求得基桩竖向极限承载力值,并与传统方法进行对比,验证了本文公式的合理性。
[Abstract]:Pile foundation is one of the most widely used foundation forms. Its main function is to bear the upper load and transfer the vertical load to the deep foundation. Therefore, the study of ultimate vertical bearing capacity is one of the most important contents in the design and calculation of pile foundation. The ultimate bearing capacity of pile is the sum of lateral resistance and end resistance. However, some field test data and laboratory model tests show that the pile side friction and end resistance are not completely independent, and there is a certain degree of interaction between the two in the process of pile loading, and this interaction. Therefore, this paper attempts to carry out laboratory simulation experiments on the effect of lateral resistance enhancement, to observe the effect of lateral resistance enhancement on the side friction of foundation piles by means of static load test of foundation piles, and to explore the law of the effect of pile diameter on this effect, and on this basis, to introduce the limit score. Analytical method is used to simulate the interaction between pile tip resistance and pile side resistance in the process of pile bearing, and a formula for calculating the ultimate vertical bearing capacity of pile foundation considering the enhancement effect of pile side resistance is proposed, which can be used for reference in optimizing pile design and further excavating the bearing potential of pile foundation. In the course of construction, the variation law of side resistance at the end of pile is monitored to verify the existence of side resistance enhancement effect. Based on the comparative test of different pile diameters, the influence of pile diameters on the side resistance enhancement effect is discussed. The results show that the side resistance enhancement effect becomes more obvious with the increase of pile diameters. The relative displacement of pile and soil at the bottom of pile, the nature of pile-soil interface, the strength of bearing layer at the end of pile, the exertion degree of pile resistance, and the complexity of soil are the factors that influence the lateral resistance enhancement. Based on the failure mode of deep foundation, the upper limit method of limit analysis is introduced to calculate the pile considering the lateral resistance enhancement effect. The formulas of vertical bearing capacity are given, and the sensitivity of each influencing factor of vertical bearing capacity of foundation pile is analyzed, and the influence law of each influencing factor on lateral resistance enhancement effect is explored. The rationality of the formula is verified by comparison.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU473.1

【引证文献】