【作者】 刘峻龙；

【导师】 赵明华； 刘晓明；

【作者基本信息】 湖南大学 ， 岩土工程， 2008， 硕士

【摘要】 随着上部结构对基础承载力和沉降等要求的愈来愈高,桩基础由于其诸多优点在工程中得到广泛应用,采用经济可靠的试验手段测定桩身竖向承载力,不仅是现有规范的要求,也是目前桩基础领域中具有重要理论与工程实际意义的课题。基桩荷载试验自锚法作为一种新的应用技术,目前尚缺乏对桩底锚杆受力特性以及桩-土-锚杆之间相互影响的系统深入研究。本文结合湖南省建设厅科技计划项目(200403),对桩和锚杆的承载机理、计算方法以及自锚体系中基桩承载力进行了探讨和分析,并在以下几个方面进行了深入研究。首先,通过对国内外有关研究文献和试验资料的综合分析,较全面地探讨和总结了桩土荷载传递和锚杆抗拔承载机理;在介绍嵌岩桩竖向承载力计算的规范法和基于圆锥体破坏模式的锚杆极限承载力计算方法的基础上,基于轴向winkler地基模型,导得了锚杆在线弹性变形时P~s曲线的斜率表达式;基于梅耶霍夫(Meyehof)假定和Touma的成拱理论,探讨了桩-土-锚杆共同作用体系中桩底锚杆对桩端阻力和桩侧摩阻力的强化作用机理。为了研究自锚测试中的桩锚相互作用,在上述理论的基础上,设计并进行基桩竖向承载力自锚测试技术的室内模型试验,分别完成了单桩竖向承载力试验、单根锚杆的抗拔试验、桩锚组合体系的加载、拉拔试验,得到了单桩在不同嵌岩深度时的荷载位移关系曲线、锚杆在拉拔荷载下的荷载位移关系、轴力分布、桩锚组合体系中桩的竖向沉降和荷载的关系曲线,并将其与理论计算值进行对比分析,同时探讨了桩底锚杆锚固长度对基桩荷载位移曲线的影响。最后,基于ADINA有限元分析软件,建立了单桩和自锚体系的二维平面模型,根据数值模拟结果并结合试验数据,得出桩底锚杆锚固长度对基桩Q~s曲线弹性段斜率、试桩极限承载力影响的经验关系式。更多还原

【Abstract】 With the increasing request of the superstructure to bearing capacity and settlement of the foundation, pile foundation has extensive application in engineering practices because of its much merit. Using an economical and effective method to test the vertical bearing capacity of pile, is not only the requirement of existing criterions, but also the topic of important theoretical and practical significance in the area of pile foundation. Presently, self-anchored loading test technology of pile foundation is a new application technology. There is a deficiency of systematic and thorough research on the mechanics property of the anchoring bolt under pile toe and the pile-soil-bolt interaction. By integrating with the Construction Technology Projects of Hunan Province(NO.200403), this paper discussed the uplift mechanism and design method of bolt, also the bearing capacity of pile foundation, in the self-anchored system. Mainly research and investigation are done as the following:Firstly, Through comprehensive analyses of the domestic and world related references and experimental data, an in-depth study and summarization of the pile-soil load transfer behavior and the uplift mechanism of bolt is obtained. Based on Introducing the calculation method offered by Code for the rock socketed pile and the bolt ultimate strength calculation method, leading the axial Winkler model into the calculation of bolt-deformation, derived the expression of the slope of the P~s curve of the bolt, based on the in-depth analyses of the pile-soil load transfer behavior and the uplift mechanism of bolt, the theoretical explanation of pile-soil-bolt interaction in the self-anchored system is obtained. And the enhanced action mechanism that the bolt under pile toe do to the pile end bearing capacity and the pile side resistance have been researched on the base of Meyehof presumption and Touma’s arch-formation theory.In order to study the self-anchored test of pile-anchor interaction, based on the theory above, design and do the vertical pile-bearing capacity of self-anchored test in the laboratory, completed a single vertical pile-bearing capacity test, a single bolt pull-out capacity test, pile-anchor combination system bearing capacity test and pull-out test, have been derived the load-displacement curve of the pile in different depth in the rock , the load-displacement curve of the anchor under the different drawing load and axial force distribution, the load-displacement curve of the pile-anchor system and compared with the theoretical value. At the same time studying the effect of e the length of the bolt at the bottem of the pile on the ultimate bearing capacity of the pile.Finally, based on the ADINA software of the finite element analysis, established the two-dimensional plane model of the self-anchored system, according to the results of numerical simulation and combined with the test data, derived the receempirical relationship between the length of anchor bolt at the bottem of pile and the slope of the Q~s curve and ultimate bearing capacity of the pile.更多还原