长期水平循环荷载下大直径桩的累积位移分析

发布时间：2018-06-30 04:47

本文选题：大直径钢管桩 + 刚度衰减　；参考：《浙江大学》2013年硕士论文

【摘要】：海上风电机组的桩基础在其正常工作的年限中,将承受来自强风荷载、波浪冲击等水平荷载的长期作用,这些低频的循环荷载将造成桩基础的永久侧向变形。当桩身转角超过0.5。,可能造成风力发电机无法正常运作。因此,研究风机桩基础在波浪等长期水平循环荷载作用下的侧向累计位移就显得尤为重要。目前,最普遍用于分析桩基础侧向变形的方法莫过于由API建议的p-y曲线分析法。该法所建议的p-y曲线是基于小口径桩基础的现场试验曲线来对桩身位移作预测,但越来越多的研究表明,p-y曲线法会严重低估大直径桩在长期受荷时的累积位移。对于大直径海上风机桩基础而言,还缺少简单有效的方法来分析其在长期水平循环荷载下的变形特性。本文的主要目的就是找到一种合适的评价方法来分析大直径钢管桩在长期水平循环荷载作用下的侧向累积位移,主要工作如下： (1)研究了无粘性土在长期荷载作用下的的变形规律,对各种累积塑性变形模型进行分析比较,采用基于室内动三轴试验的刚度衰减模型来评价无粘性土的长期动力特性,并对现有的刚度衰减模型进行了改进。 (2)分析砂土室内动三轴试验的数据,得到了刚度衰减模型的回归参数,然后对有限元软件ABAQUS进行二次开发以实现土体刚度的衰减,并将数值计算的结果与室内单元体试验结果进行了对比,最后分析评价了模型各个参数对计算结果的影响。 (3)建立了大直径单桩基础的三维有限元模型,将土体刚度衰减模型嵌入其中,研究单桩基础在长期水平循环荷载作用下的侧向位移发展情况,重点分析了大直径桩的桩径、嵌入深度、循环次数、荷载频率及荷载大小等对单桩基础水平位移的影响,得到了一些规律性的结论。并与室内模型桩试验结果进行对比,验证了刚度衰减模型的有效性。
[Abstract]:In the normal working life of offshore wind turbine the pile foundation will bear the long-term action of horizontal load such as strong wind load wave impact and so on. These low-frequency cyclic loads will cause permanent lateral deformation of pile foundation. When the rotation angle of the pile is greater than 0.5, the wind turbine may not work properly. Therefore, it is very important to study the lateral accumulative displacement of fan pile foundation under the action of wave and other long-term horizontal cyclic loads. At present, the most popular method for analyzing lateral deformation of pile foundation is the p-y curve analysis method recommended by API. The p-y curve proposed by the method is based on the field test curve of the small diameter pile foundation to predict the displacement of the pile body. However, more and more studies show that the p-y curve method will seriously underestimate the cumulative displacement of the large diameter pile under long-term loading. For large diameter offshore fan pile foundation, there is a lack of simple and effective method to analyze its deformation characteristics under long-term horizontal cyclic load. The main purpose of this paper is to find a suitable evaluation method to analyze the lateral cumulative displacement of large diameter steel pipe piles under long-term horizontal cyclic loading. The main works are as follows: (1) the deformation law of cohesive soil under long-term load is studied, and various cumulative plastic deformation models are analyzed and compared. The stiffness attenuation model based on indoor dynamic triaxial test is used to evaluate the long-term dynamic characteristics of cohesive soil, and the existing stiffness attenuation model is improved. (2) the data of indoor dynamic triaxial test of sandy soil are analyzed. The regression parameters of the stiffness attenuation model are obtained, and then the finite element software Abaqus is developed twice to realize the soil stiffness attenuation, and the numerical results are compared with the results of the indoor element test. Finally, the influence of various parameters of the model on the calculation results is analyzed and evaluated. (3) the three-dimensional finite element model of large diameter single pile foundation is established, and the soil stiffness attenuation model is embedded in the model. The development of lateral displacement of single pile foundation under long term horizontal cyclic load is studied. The influence of pile diameter, embedded depth, cycle number, load frequency and load on the horizontal displacement of single pile foundation is analyzed. Some regular conclusions are obtained. The validity of the stiffness attenuation model is verified by comparing with the results of indoor model pile test.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU473.1

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