三维饱和介质粘弹性人工边界

发布时间：2018-03-28 04:22

本文选题：饱和介质　切入点：三维粘弹性人工边界　出处：《中国水利水电科学研究院》2015年硕士论文

【摘要】：强震作用下土坝、土体边坡及其地基会产生液化失稳问题,因此对其进行抗震安全评价理应将土体看作由土骨架和孔隙水两相材料组成。动力分析不仅要给出土骨架的位移时程还要计算出孔隙水压力的变化时程。与单相固体结构的人工粘弹性边界不同,对于饱和土体的人工边界,除了要处理位移边界条件外,还要考虑孔隙水压力在人工边界的传播。本文在总结当前国内外人工边界处理方法研究成果的基础上,建立了具有粘弹性人工边界的三维饱和介质动力学虚位移原理。同时,基于有限元自动生成系统(FEPG),开发了具有粘弹性人工边界的三维饱和介质动力固结方程计算程序。利用该程序讨论了冲击荷载、突加荷载以及地震荷载作用下土体地位移、速度、加速度和孔隙水压力的扩散过程。主要研究内容包括：(1)基于辛克维奇(Zienkiewicz)的基本假设,认为土是固体骨架和介质液组成的两相体,忽略流体中的压缩波,以饱和介质动力固结方程的u-p形式为基本方程。按照球面波阵面上的位移和应力与人工边界上的应力和位移的等效关系,推导并给出了三维饱和介质粘弹性人工边界的边界条件和边界上的流量公式；(2)基于虚位移原理建立了加粘弹性人工边界的三维饱和介质动力固结控制方程的积分弱解形式,并对照一般粘弹性人工边界的地震动输入,根据有效应力原理给出了饱和介质粘弹性人工边界上的地震动输入方法；(3)根据建立的动力固结控制方程弱解形式,基于有限元自动生成系统编写脚本文件,开发了三维饱和介质粘弹性人工边界动力计算有限元程序,通过算例证明了所建立方程的正确性和程序的可行性。本文最后对孔压吸收边界和介质阻尼对计算结果的影响,以及地震波作用下的饱和地基位移和孔隙水压扩散进行了研究。
[Abstract]:Under the action of strong earthquake, the soil slope and its foundation will cause liquefaction instability problem. Therefore, the seismic safety evaluation should regard soil mass as composed of soil skeleton and pore water. Dynamic analysis should not only give displacement time history of unearthed skeleton, but also calculate the time history of pore water pressure change. The artificial viscoelastic boundaries of solid structures are different. For the artificial boundary of saturated soil, in addition to the displacement boundary condition, the propagation of pore water pressure at the artificial boundary should be considered. The virtual displacement principle of three-dimensional saturated media with viscoelastic artificial boundary is established. Based on the finite element automatic generating system (FEPGN), a three-dimensional saturated medium dynamic consolidation equation calculation program with viscoelastic artificial boundary is developed. By using the program, the earth displacement and velocity under impact load, sudden addition load and earthquake load are discussed. Acceleration and pore water pressure diffusion process. The main research contents include: 1) based on the basic hypothesis of Sinkevich Zienkiewicz), the soil is considered as a two-phase body composed of solid skeleton and medium liquid, and the compression wave in fluid is ignored. Taking u-p form of dynamic consolidation equation of saturated medium as the basic equation, according to the equivalent relation between the displacement and stress on the spherical wave front and the stress and displacement on the artificial boundary, In this paper, the boundary conditions of three-dimensional viscoelastic artificial boundary and the flow rate formula on the boundary are derived and given. Based on the virtual displacement principle, the integral weak solution of the three-dimensional saturated medium dynamic consolidation control equation with viscoelastic artificial boundary is established. According to the principle of effective stress, the input method of ground motion on the artificial boundary of saturated medium is given according to the input of the general viscoelastic artificial boundary, and the weak solution of the governing equation of dynamic consolidation is established. Based on the automatic generating system of finite element, the script file is written, and the finite element program for dynamic calculation of three dimensional viscoelastic artificial boundary in saturated medium is developed. An example is given to prove the correctness of the equation and the feasibility of the program. Finally, the influence of pore pressure absorbing boundary and medium damping on the calculation results, and the displacement of saturated foundation and pore water pressure diffusion under the action of seismic wave are studied.
【学位授予单位】：中国水利水电科学研究院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU435

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