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首页> 外文学位 >Nonlinear analysis of pile driving and ground vibrations in saturated cohesive soils using the finite element method.
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Nonlinear analysis of pile driving and ground vibrations in saturated cohesive soils using the finite element method.

机译：使用有限元方法对饱和黏性土中的打桩和地面振动进行非线性分析。

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摘要

In urban areas, vibrations generated by pile driving often affect the neighboring properties vulnerable to ground shaking. These vibrations may cause damage to surrounding structures either by shaking the ground or by causing settlement of the soil beneath foundations in the proximity of pile driving. It is important to distinguish between the conditions under which the vibrations will cause damage and those under which vibrations are tolerable. The numerical studies on the analysis of pile driving have mostly focused on assessing the driving efficiency and the bearing capacity of dynamically loaded piles. A limited number of studies included the study of ground vibrations due to pile driving and its effects on adjacent structures. However, the factors affecting the ground vibrations in soils such as the nonlinear constitutive behavior of soil, soil-pile interaction and penetration depth of the pile have not been clearly identified.;The objective of this research is to implement a numerical method to simulate dynamic loading of a single pile, and study the factors influencing the stress wave propagation in the soil surrounding the pile. The thesis is comprised of two main analyses: (1) the static analysis of a pile in which the phenomenon of static consolidation is studied, and (2) the dynamic analysis of a pile in which pile driving and ground vibrations are studied.;In the static analysis, the load capacity of a single pile is investigated. The results from the finite element method are compared with widely recognized theoretical methods. The theoretical methods that are used to estimate the end bearing capacities are: (1) General Formula, (2) Vesic's Method, (3) Janbu's Method, (4) Meyerhof's Method, and (5) Coyle & Castello's Method. The estimation of skin friction resistance (shaft capacity) of single piles is performed using the (1) Alpha method, (2) Beta method, and (3) Lambda method. Two numerical applications are performed to predict the load capacity of single piles in normally consolidated clays. It is observed that the model with no slippage at the interface predicts almost twice as much load capacity as the model with interface. In regards with the end bearing capacities, Coyle & Castello's method is found to be most conservative followed by the finite element method, the Janbu's method, the Meyerhof's method, and finally the Vesic's method. In respect to skin friction resistance, the finite element is found to be the most conservative method, followed by the Beta, the Lambda, and the Alpha method.;In the dynamic analysis, the amplitudes of ground vibrations are investigated based on the variation of: (1) the soil type, (2) the pile embedment length and (3) the released hammer energy. In the first analysis, five types of soils -- loose and dense sands and, soft, medium stiff, and stiff clays -- are modeled. The highest vibration amplitude is calculated for the loose sand with a peak particle velocity (PPV) of 10.0 mm/s followed by the dense sand with a PPV of around 4.0 mm/s. Among the clay types, the vibrations are higher for the stiffer clay in the near field, which is 9 m (half a pile length) or less away from the pile. In the second analysis, three different embedment lengths -- full, half, and quarter pile length -- are modeled. It is found that the quarter embedded piles produce greater vibration amplitudes as compared to the half and fully embedded piles. Larger amplitudes of vibrations are encountered on the ground surface for shorter pile embedment lengths. In the third analysis, three different impact forces consisting of 2,000 kN (F), 6,000 kN (3F) and 10,000 kN (5F) are applied on the pile head. It is concluded that increase in hammer energy causes increase in the peak particle velocities.
机译：在城市地区，打桩产生的振动通常会影响容易受到地面震动影响的邻近属性。这些振动可能通过摇动地面或在打桩附近使地基下方的土壤沉降而损坏周围的结构。重要的是要区分振动会导致损坏的条件和容许振动的条件。关于打桩分析的数值研究主要集中在评估动力加载桩的驱动效率和承载力上。有限的研究包括由于打桩引起的地面振动及其对相邻结构的影响的研究。然而，尚未明确识别出影响土壤中地面振动的因素，例如土壤的非线性本构行为，土桩相互作用以及桩的穿透深度。；本研究的目的是实现一种数值方法来模拟动力并研究影响应力波在桩周围土壤中传播的因素。本文主要包括两个方面的分析：（1）对桩的静力分析进行了静力固结现象的研究；（2）对桩的动力分析进行了对桩的动力和地面振动的研究。通过静力分析，研究了单桩的承载能力。将有限元方法的结果与公认的理论方法进行了比较。用于估计端部承载力的理论方法是：（1）通式，（2）Vesic方法，（3）Janbu方法，（4）Meyerhof方法和（5）Coyle＆Castello方法。使用（1）Alpha方法，（2）Beta方法和（3）Lambda方法估算单桩的皮肤摩擦阻力（轴承载力）。进行了两个数值应用来预测正常固结粘土中单桩的承载能力。可以看出，在界面处没有滑动的模型预测的承载能力几乎是在具有界面的模型中的两倍。关于最终承载力，发现Coyle＆Castello方法最保守，其次是有限元方法，Janbu方法，Meyerhof方法，最后是Vesic方法。就皮肤摩擦阻力而言，有限元法是最保守的方法，其次是Beta，Lambda和Alpha方法。在动力学分析中，基于的变化来研究地面振动的振幅。 ：（1）土壤类型，（2）桩的包埋长度和（3）释放的锤击能量。在第一个分析中，对五种类型的土壤进行了建模-疏松密实的沙子以及软，中硬和硬粘土。对于峰值速度（PPV）为10.0 mm / s的疏松砂，随后是PPV为约4.0 mm / s的致密砂，计算出最大振动幅度。在黏土类型中，较硬的黏土在近场中的振动较高，该振动距离桩体9m（桩长的一半）或更短。在第二个分析中，对三种不同的嵌入长度（完整，一半和四分之一桩长度）进行了建模。发现与四分之一和全埋桩相比，四分之一埋桩产生更大的振动幅度。对于较短的桩嵌入长度，在地面上会遇到较大的振动幅度。在第三次分析中，在桩头上施加了由2,000 kN（F），6,000 kN（3F）和10,000 kN（5F）组成的三种不同的冲击力。结论是，锤能量的增加引起峰值粒子速度的增加。

著录项

  • 作者

    Serdaroglu, Mehmet Serdar.;

  • 作者单位

    The University of Iowa.;

  • 授予单位 The University of Iowa.;
  • 学科 Engineering Civil.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 265 p.
  • 总页数 265
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-17 11:36:56

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