Gibson地基中V-T联合受荷桩承载力分析与试验研究

发布时间：2018-01-14 14:45

本文关键词：Gibson地基中V-T联合受荷桩承载力分析与试验研究　出处：《湖南大学》2015年硕士论文　论文类型：学位论文

【摘要】：桩基础因其承载力高、沉降小、施工方便以及能适应复杂地质环境等优点在基础工程中被广泛使用。对于城市立交桥、跨江跨海大桥、海上钻井平台或风力发电塔等结构物中的桩基础,除承受竖向荷载V外,又由于桩顶的不均匀或偏心水平力、侧向冲击荷载或地震等因素的影响而作用有较大扭矩。现有的常规设计方法难以考虑这种竖向力V与扭矩T的共同作用,导致难以合理地评价桩身承载力,有时甚至使设计偏于不安全而危及上部结构。为此,本文基于已有研究工作和成果,结合国家自然科学基金项目(51378197),针对广义Gibson地基中的V-T联合受荷桩进行了理论分析与室内模型试验研究,主要工作如下:首先,针对Gibson地基中的竖向受荷桩与受扭桩,视桩身和桩周土分别为弹性体和理想弹塑性体,基于剪切位移法和桩身荷载传递函数建立出桩身位移控制方程,并考虑桩-土接触面上的位移非协调性,引入桩底力和位移边界条件后,推导出由Bessel函数表示的桩周土处于不同受力阶段时的桩身内力位移解答,并将其计算结果与已有研究成果进行了对比分析,验证本文方法的可行性。其次,基于获得的竖向受荷桩与受扭桩解答,针对桩周土体分别处于弹性→弹性、弹性→弹塑性及弹塑性→弹塑性三个不同阶段,同时考虑V-T联合受荷桩的不同加载路径(V→T与T→V),导得了V-T联合受荷桩的内力位移解答,并求解出不同加载路径下的桩身极限联合承载力。然后,基于Mathcad编制出相应的计算程序,由此完成的参数分析探讨了桩身长径比L/D、桩土弹性模量比λ、桩侧土体的剪切模量和极限侧阻力分布常数比n对桩身承载力的影响规律,进而获得了不同加载路径下的桩身承载力包络线。最后,通过自制砂箱和滑轮组加载装置,完成了砂土中单桩分别在纯扭矩荷载与V-T联合荷载作用下的室内载荷模型试验,获得了相应的桩顶荷载-变形、桩身内力位移及桩身极限承载力,并将试验结果与本文理论分析值进行了对比分析和验证。
[Abstract]:Pile foundation is widely used in foundation engineering because of its high bearing capacity, small settlement, convenient construction and can adapt to complex geological environment. The pile foundation in offshore drilling platform or wind power tower is not only subjected to vertical load V, but also due to the uneven or eccentric horizontal force on the top of pile. Due to the influence of lateral impact load or earthquake, the existing conventional design method is difficult to consider the interaction of vertical force V and torque T, which makes it difficult to evaluate the bearing capacity of pile body reasonably. Sometimes even the design is unsafe and endangers the superstructure. Therefore, this paper based on the existing research work and results, combined with the National Natural Science Foundation Project 51378197). The theoretical analysis and indoor model test of V-T combined loaded pile in generalized Gibson foundation are carried out. The main work is as follows: first. In view of vertical loaded pile and torsional pile in Gibson foundation, the pile body and surrounding soil are regarded as elastic body and ideal elastoplastic body, respectively. Based on the shear displacement method and the load transfer function of the pile body, the displacement control equation of the pile body is established. Considering the disharmony of the displacement on the pile-soil interface, the boundary conditions of the pile bottom force and displacement are introduced. In this paper, the displacement solutions of the internal force of the soil around the pile under different loading stages are derived by Bessel function, and the calculated results are compared with the existing research results. The feasibility of this method is verified. Secondly, based on the solutions of vertical loaded pile and torsional pile, the soil around pile is elastic respectively. 鈫扙lasticity. 鈫扙lastoplasticity and elastoplasticity. 鈫扵hree different stages of elastoplasticity and consideration of different loading paths of V-T combined loaded piles. 鈫扵 and T. 鈫扵he internal force displacement solution of V-T combined loaded pile is obtained, and the ultimate joint bearing capacity of pile body under different loading paths is solved. Then, the corresponding calculation program based on Mathcad is worked out. The influence of the ratio of length to diameter of pile, the ratio of elastic modulus of pile to soil, the shear modulus of soil around the pile and the distribution constant ratio of ultimate lateral resistance to the bearing capacity of pile are discussed. Then the envelope of pile bearing capacity under different loading paths is obtained. Finally, the self-made sand box and pulley loading device are used. The indoor load model tests of single pile in sand under the combined load of pure torque and V-T have been completed, and the corresponding load-deformation of pile top, displacement of internal force and ultimate bearing capacity of pile body have been obtained. The experimental results are compared and verified with the theoretical analysis in this paper.
【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

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