可液化场地土与地下结构地震动力响应的研究
发布时间：2019-05-30 08:53
【摘要】：论文以有限元软件Midas GTS和有限差分软件FLAC3D作为主要平台,利用FLAC3D和Midas建立土与地下结构相互作用的模型。之后通过FLAC3D进行计算,分别就含水率和地下水位改变对地下结构及土体的地震反应的影响进行了探讨。最后对在可液化场地下不同因素对地下结构动力响应的影响进行了研究,主要的研究成果如下:1.论文的第一部分阐述了含水率对土体的弹性模量、黏聚力、内摩擦角以及土体密度的影响。发现密实度一定的情况下,黏性土的多种力学参数会随着最佳含水率的出现而出现“峰值”效应。本部分利用FLAC3D差分软件对不饱和土在地震作用下的动力响应进行了模拟和分析,探讨了土中含水率对于地下结构地震动力响应的影响规律。结果表明:(1)在最佳含水率附近,土层的性质对于土与地下结构的作用来说是最良好的,此时结构的内力可取得最小值;(2)顶板和底板的相对水平位移变化不大,并且在最佳含水率之前位移的数值随着含水率的增加而逐渐减小;(3)土体和结构的加速度峰值都随着含水率的增加而呈减小的趋势。2.论文的第二部分利用FLAC3D软件,把土与地下结构的相互作用问题视为平面应变问题,采用Mohr-Coulomb本构模型和Finn本构模型分别来描述处于水位线上、下土体的非线性动力特性和孔隙压力的发展规律,对地震作用下土与地下结构的相互作用不同工况进行了数值模拟。结果表明:(1)水位线上升,孔隙压力大幅度提高,孔压比增加,结构周围土体更容易发生液化;(2)上下板和中柱的加速度峰值产生时刻与地震波峰值产生的时刻相同,而且水位变化对上下板和中柱的加速度影响不明显;(3)底板两角隅处的应力大于中柱的应力,并且底板的主应力都随着地下水位的提升而增大。3.论文的第三部分就三个影响因素:对不同结构截面形式、水平-竖向波共同作用、不同地震波输入对地下结构的动力响应的影响进行了研究,结果如下:(1)确定了在地震作用下处于可液化场地的拱形结构和矩形结构的应力的分布和最不利受力位置;(2)模型分别在竖向地震波以及横向地震波单独和共同作用下,孔压比幅值也不相同,总体来讲,水平和竖向波共同作用下的孔压比更大一些;(3)峰值不同的地震波对结构的应力的分布影响不大,却对结构加速度影响十分显著。4.论文的第四部分,对本文的研究成果进行了总结,指出了需要进一步研究的问题,并且建议了改进思路和方法。
[Abstract]:In this paper, the finite element software Midas GTS and the finite difference software FLAC3D are used as the main platforms to establish the model of the interaction between soil and underground structure by using FLAC3D and Midas. Then the effects of water content and groundwater level on the seismic response of underground structure and soil are discussed by FLAC3D calculation. Finally, the effects of different factors on the dynamic response of underground structures under liquefied sites are studied. The main research results are as follows: 1. In the first part of the paper, the effects of moisture content on elastic modulus, cohesion, internal friction angle and soil density are described. It is found that under the condition of certain compactness, a variety of mechanical parameters of clay will appear "peak" effect with the appearance of optimal moisture content. In this part, the dynamic response of saturated soil under earthquake is simulated and analyzed by using FLAC3D difference software, and the influence of soil moisture content on seismic dynamic response of underground structure is discussed. The results show that: (1) near the optimum moisture content, the properties of soil layer are the best for the action of soil and underground structure, and the internal force of the structure can obtain the minimum value at this time; (2) the relative horizontal displacement of roof and floor does not change much, and the value of displacement decreases with the increase of moisture content before the optimum moisture content; (3) the peak acceleration of soil and structure decreases with the increase of moisture content. 2. In the second part of the paper, the interaction between soil and underground structure is regarded as a plane strain problem by using FLAC3D software, and the Mohr-Coulomb Constitutive Model and Finn Constitutive Model are used to describe the interaction between soil and underground structure on the water level line, respectively. The nonlinear dynamic characteristics of soil and the development of pore pressure are studied by numerical simulation of the interaction between soil and underground structure under earthquake. The results show that: (1) when the water level line rises, the pore pressure increases greatly, and the pore pressure ratio increases, the soil around the structure is more prone to liquefaction; (2) the peak acceleration time of upper and lower plate and middle column is the same as that of seismic wave, and the influence of water level change on the acceleration of upper and lower plate and middle column is not obvious; (3) the stress at the corner of the bottom plate is greater than that of the middle column, and the principal stress of the floor increases with the increase of groundwater level. In the third part of the paper, three influencing factors are studied: the interaction of different structural sections, horizontal and vertical waves, and the influence of different seismic wave inputs on the dynamic response of underground structures. The results are as follows: (1) the stress distribution and the most unfavorable stress position of arch structure and rectangular structure in liquefaction site under earthquake action are determined. (2) under the action of vertical seismic wave and transverse seismic wave, the amplitude of pore pressure ratio is different, and the pore pressure ratio is larger under the combined action of horizontal and vertical waves. (3) the seismic waves with different peaks have little effect on the stress distribution of the structure, but have a significant effect on the acceleration of the structure. 4. In the fourth part of the paper, the research results are summarized, the problems that need to be further studied are pointed out, and the improvement ideas and methods are suggested.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU435
本文编号：2488704
[Abstract]:In this paper, the finite element software Midas GTS and the finite difference software FLAC3D are used as the main platforms to establish the model of the interaction between soil and underground structure by using FLAC3D and Midas. Then the effects of water content and groundwater level on the seismic response of underground structure and soil are discussed by FLAC3D calculation. Finally, the effects of different factors on the dynamic response of underground structures under liquefied sites are studied. The main research results are as follows: 1. In the first part of the paper, the effects of moisture content on elastic modulus, cohesion, internal friction angle and soil density are described. It is found that under the condition of certain compactness, a variety of mechanical parameters of clay will appear "peak" effect with the appearance of optimal moisture content. In this part, the dynamic response of saturated soil under earthquake is simulated and analyzed by using FLAC3D difference software, and the influence of soil moisture content on seismic dynamic response of underground structure is discussed. The results show that: (1) near the optimum moisture content, the properties of soil layer are the best for the action of soil and underground structure, and the internal force of the structure can obtain the minimum value at this time; (2) the relative horizontal displacement of roof and floor does not change much, and the value of displacement decreases with the increase of moisture content before the optimum moisture content; (3) the peak acceleration of soil and structure decreases with the increase of moisture content. 2. In the second part of the paper, the interaction between soil and underground structure is regarded as a plane strain problem by using FLAC3D software, and the Mohr-Coulomb Constitutive Model and Finn Constitutive Model are used to describe the interaction between soil and underground structure on the water level line, respectively. The nonlinear dynamic characteristics of soil and the development of pore pressure are studied by numerical simulation of the interaction between soil and underground structure under earthquake. The results show that: (1) when the water level line rises, the pore pressure increases greatly, and the pore pressure ratio increases, the soil around the structure is more prone to liquefaction; (2) the peak acceleration time of upper and lower plate and middle column is the same as that of seismic wave, and the influence of water level change on the acceleration of upper and lower plate and middle column is not obvious; (3) the stress at the corner of the bottom plate is greater than that of the middle column, and the principal stress of the floor increases with the increase of groundwater level. In the third part of the paper, three influencing factors are studied: the interaction of different structural sections, horizontal and vertical waves, and the influence of different seismic wave inputs on the dynamic response of underground structures. The results are as follows: (1) the stress distribution and the most unfavorable stress position of arch structure and rectangular structure in liquefaction site under earthquake action are determined. (2) under the action of vertical seismic wave and transverse seismic wave, the amplitude of pore pressure ratio is different, and the pore pressure ratio is larger under the combined action of horizontal and vertical waves. (3) the seismic waves with different peaks have little effect on the stress distribution of the structure, but have a significant effect on the acceleration of the structure. 4. In the fourth part of the paper, the research results are summarized, the problems that need to be further studied are pointed out, and the improvement ideas and methods are suggested.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU435
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