循环荷载作用下考虑软基弱化效应时防波堤的稳定性分析

发布时间：2018-01-05 20:19

本文关键词：循环荷载作用下考虑软基弱化效应时防波堤的稳定性分析　出处：《天津大学》2014年硕士论文　论文类型：学位论文

【摘要】：近年来，随着我国港口规模扩大与海洋空间的日益开发、利用，离岸深水港口的建设是水运交通事业的一个重要发展方向，同时也面临着更恶劣的环境条件。一方面海况环境更复杂，波浪条件更恶劣；另一方面地基条件多为软黏土，承载能力低。因此，工程中除了开发适于软土地基的轻型结构形式外，，软黏土在波浪荷载的循环作用下发生弱化引起地基承载能力大幅降低从而影响结构物的稳定性也是亟待深入研究的问题。本文针对这些问题，以天津港软黏土作为研究对象，对循环荷载作用下软黏土强度弱化的动态规律以及在此基础上结构物的稳定性分析开展了一系列研究，主要工作内容如下： 1．将现有的天津港原状软黏土孔压发展模型、抗剪强度折减规律与等效超固结比公式结合，拟合得到软黏土在不同应力组合状态下强度衰减的变化规律，这个规律反应了软黏土的抗剪强度随循环周期的动态衰减过程。 2．利用ABAQUS建立三维弹塑性模型，在ABAQUS平台上进行二次开发，编写材料参数同场变量随时间变化的用户子程序，将拟合得到的软黏土强度衰减的动态变化规律体现在土体c、两个指标上，建立基于M-C屈服准则的地基循环强度分析模型。 3．运用考虑了软基循环弱化效应的有限元模型对防波堤的稳定性进行动力、拟静力分析，并与未考虑软基弱化的动力、静力有限元分析结果进行对比，通过比较不同研究模型的有限元结果，说明软土的循环弱化效应严重影响结构的稳定性，要在实际工程中引起足够的重视。 4．研究多种相关因素对防波堤结构动力、静力稳定性的影响，分别从结构入土深度、地基土性指标等方面取若干工况进行有限元分析，在此基础上提出提高结构稳定性的经济有效措施。 5．在对结构进行稳定性分析时，不同的失稳判别准则对应不同的结构安全系数，为了同时满足土体强度和结构变位两方面的要求，本文通过有限元分析，针对不同的地基土体对结构失稳准则的选取提供合理的参考建议，并在现有的失稳判别准则上提出一些改进。
[Abstract]:In recent years , with the expansion of port scale and the development and utilization of ocean space , the construction of offshore deep - water port is an important development direction of water transportation and transportation . 1 . The existing soft clay hole pressure development model , shear strength reduction rule and equivalent hyperconsolidation ratio formula are combined to obtain the change law of strength attenuation in soft clay under different stress combinations . This law reflects the dynamic attenuation process of the shear strength of soft clay with the cycle period . 2 . A three - dimensional elastic - plastic model is established by means of finite element method , and a user sub - routine is developed on the basis of two indexes , which is based on the M - C yield criterion , and the dynamic change rule of the intensity attenuation of the soft clay obtained by fitting is reflected on the c and the two indexes of the soil body . 3 . The finite element model considering the weakening effect of soft soil circulation is used to analyze the stability of breakwater , and the dynamic and static finite element analysis results of soft soil weakening are compared . By comparing the finite element results of different research models , it is shown that the cyclic weakening effect of soft soil seriously affects the stability of the structure , which should pay enough attention in practical engineering . 4 . The influence of many relevant factors on the dynamic and static stability of breakwater is studied . 5 . When the stability of the structure is analyzed , the different criterion of instability criterion corresponds to different structural safety factors . In order to meet the requirements of both soil strength and structural displacement , this paper provides a reasonable reference for the selection of structural instability criterion for different foundation soils by finite element analysis , and puts forward some improvements on the existing criterion of instability criterion .

【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U656.2

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