【作者】 邹德高；

【导师】 孔宪京；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2008， 博士

【摘要】 地震时,浅埋地下管线的破坏主要是由于地基液化引起管线上浮所导致的,研究地震时地下管线上浮机理及减灾对策是岩土工程和生命线工程的重要课题。本文结合国家自然科学基金项目《地震时浅埋地下管线上浮机理及减灾对策研究》(50278009)和《饱和砂砾土的液化特性及变形、强度参数的相关性研究》(50578029),围绕了饱和砂土地基中浅埋地下管线上浮机理及其影响因素、饱和土非线性有限元程序开发、饱和土有效应力分析方法、减轻地下管线震害的工程措施等进行了较为深入的研究。论文的主要研究内容如下:(1)通过类比的试验方法,精心设计了一系列的振动台模型试验,着重观察了饱和砂土地基的地震加速度反应、振动孔隙水压力的产生和消散过程,初步探讨了地震时地下管线上浮机理和几种不同排水(或加固)措施对抑制管线上浮的效果。(2)利用Windows开发平台,采用面向对象设计方法和Visual C++MFC开发工具开发了饱和土非线性有限元程序GEODYNA及其有限元后处理软件POST2D。GEODYNA引入了多核并行计算、命令式输入等一些先进技术,实现了大量的本构模型和单元类型。通过对饱和土的一维固结问题和动力问题进行数值模拟,验证了GEODYNA计算结果的可靠性。这些程序为进一步深入研究饱和地基中地下管线上浮机理和减灾措施奠定了数值分析基础。(3)在广义Biot固结方程的基础上,联合采用等效线性粘弹性模型和Seed建议的孔压模型,建立了饱和砂土地基的动力固结有效应力分析方法。据此,对振动台模型试验的部分工况进行了数值模拟,进一步研究了管线上浮机理,并对抗上浮措施的效果进行了评价。(4)基于总应力分析方法,联合采用等效线性粘弹性分析方法和液化流动变形分析方法,对地下管线的上浮反应进行分析,并讨论了管线直径、埋深、地下水位、地基土相对密度等因素对地下管线上浮位移的影响。(5) GEODYNA框架中实现了广义Biot固结原理和Pastor-Zienldewicz Mark-Ⅲ广义塑性模型为基础的有效应力分析方法,模拟了饱和砂土地基中地下管线的上浮过程及抗上浮措施的效果,进一步研究了U形碎石排水对液化土中地下管线上浮的减灾效果及机理,并讨论了排水措施竖向排水带宽度、竖向排水带与管线的距离、水平排水带厚度、排水碎石渗透系数等因素对管线上浮位移的影响。更多还原

【Abstract】 The uplift of pipelines buried at shallow depth in liquefiable soil due to earthquake induced liquefaction may lead to severe damage. The study of uplifting mechanism and mitigation measurement of pipelines is important subject for geotechnical engineering and lifeline engineering. The present research is supported by the National Science Foundation Project-Study on Uplifting Mechanism and Mitigation Measurement of the Pipelines Buried at Shallow Depth during the Earthquake (No. 50278009) and the National Science Foundation Project-Study on Liquefaction and Relationship Between Parameters of Deformation and Strength of Saturated Sand-gravel Composites (No. 50578029). The main contents of the current research are as follows:(1) A series of shaking table tests are conducted by analogy method. The acceleration and excess pore water pressure response behaviors of soil foundations are studied. The uplift mechanism of pipeline and the effectiveness of different types of drainage or reinforcement measures are discussed.(2) Based on the Windows Operation System and Visual C++ MFC development tools, a saturated soil nonlinear FEM program-GEODYNA and its post-process program-POST2D are implemented by the Object-oriented method. Some advanced techniques are adopted in GEODYNA, such as Multi-Core parallel computing, command line input. A lot of soil models and FEM elements are implemented in GEODYNA. GEODYNA is verified by using analytical solution for one-dimensional saturated porous elastic consolidation and dynamic problem, and it is shown that the accuracy of the numerical solution is comfortably high.(3) An effective stress Finite Element Method is implemented for simulating the shake table test on pipelines buried in the saturated sand foundation. This method is based on generalized Biot’s equations. The hyperbolic stress and strain relationship is used in the numerical model. Pore pressure generation due to earthquake loading is calculated via the pore pressure model developed by Seed et al. The excess pore water pressure response behaviors of soil foundations, the effectiveness of different types of drainage measures arecompared with the results of tests.(4) The floation of pipelines is analyzed by the equivalent linear method and liquefaction flow method. The effects of diameter and depth of pipelines, groundwater level, and relative density of soil on the uplift behavior are studied.(5) On the base of generalized Biot theory of consolidation and Pastor-Zienkiewicz Mark-Ill generalized plasticity constitutive model, the effective stress Finite Element Procedure is implemented in the frame of GEODYNA, which is used to study the effectiveness of gravel drainage as mitigation method against the uplift of pipelines buried in liquefiable soil. Some parametric studies are conducted to investigate the influence factors of pipeline floatation, including the width of vertical drainage, the distance between vertical drainage and pipeline, the thickness of horizontal drainage, and the permeability of drainage.更多还原