【作者】 孙超；

【导师】 薄景山；

【作者基本信息】 中国地震局工程力学研究所 ， 岩土工程， 2009， 博士

【摘要】 随着全球经济建设的快速发展,地下空间的利用已经成为学术界重要的研究课题。越来越多的震害表明,地下结构在强震作用下并不一定安全,甚至发生严重破坏。1985年墨西哥8.1级地震,1995年日本7.2级阪神地震以及2008年我国四川汶川8.0级地震都造成了大量的地下结构的损坏。研究地震作用下地下结构的稳定问题是当前岩土工程研究的热点课题之一,具有重要的理论和实际意义。地铁是现代城市的重要交通工具,是公众较为集中的地下空间,其安全稳定性受到了政府和社会的极大关注。本文以地铁地下结构为研究对象,对地下结构抗震研究的主要方法进行了系统的总结,对其中存在的问题及发展方向进行了讨论和评述;对三维有限差分程序FLAC3D的基本原理、功能及其在岩土工程抗震中的应用进行了详细的介绍;对地铁地下结构的抗震性能、震害机理以及实用抗震分析方法进行了深入的研究,主要成果如下:1、将混凝土损伤本构模型应用到地下结构抗震分析中。基于混凝土损伤力学理论,采用Mazars提出的混凝土损伤演化方程确定的损伤变量,在德鲁克-普拉格本构模型的基础上,提出了一种能够考虑混凝土损伤后材料强度、刚度等参数发生相应折减的损伤本构模型(Damage_Model)。并在FLAC3D提供的用户二次开发环境的基础上,采用VC++开发出该本构模型,最后通过数值模拟试验比较了该损伤本构模型与德鲁克-普拉格模型的差异,说明了该损伤本构模型的优点。并通过采用该本构模型分析大开地铁车站的破坏机理,结果与实际震害吻合较好,从而在一定程度上验证了该损伤本构模型的适用性。2、利用本文开发的本构模型成功的模拟了日本神户大开地铁车站地震破坏过程并对破坏机理进行了解释。本文介绍了阪神地震中大开地铁车站的震害情况,以FLAC3D软件为基础,采用本文开发的混凝土损伤本构模型描述车站结构的本构特性,分析了日本神户大开地铁车站的动力反应特性及破坏过程。在车站结构与周围土层间设置了接触面单元,较好的模拟了震动过程中结构与土层的接触、脱开、滑移。认识到竖向地震动加大了地下结构所受竖向应力峰值,加速了车站中柱的损伤破坏,是导致大开地铁车站破坏的重要因素;中柱是大开地铁车站结构中的抗震薄弱环节,日本神户大开地铁车站的破坏机理可以解释为,在水平和竖向地震动共同作用下,车站结构的损伤破坏从中柱最先开始,受损的中柱逐渐失去了支撑上部荷载的能力,从而使得车站结构顶板承担巨大的上覆土层压力,逐渐在顶板与侧墙位置处发生塑性破坏,最后顶板以至于车站结构整体垮塌。3、对地下结构振动特性及其影响因素进行了较为系统的研究,总结了地下结构振动特性的基本特征。对地下结构与地面结构的动力反应特性进行了比较,认识到周围土层的约束作用使得地下结构振动特性与地面结构完全不同;对地震中地下结构所受动土压力及结构与土层的相对位移情况作了专项研究,揭示了动土压力及地下结构相对位移的变化规律;研究了竖向地震动作用下地下结构的振动特性,发现地下结构顶、底板处竖向应力远大于土中相应深度位置处的竖向应力;研究了覆盖土层厚度对于地下结构顶底板水平位移差的影响,结果表明,当覆盖土层厚度超过地下结构高度后,结构水平位移差随覆盖土层厚度程线性增长规律;最后分析了地下结构的存在对于周围场地水平及竖向加速度反应的影响。4、提出了一种适用于求解剪切波作用下地下结构顶底板水平位移差峰值的实用抗震分析方法---等效侧移刚度比法。依据不同的地下结构侧移刚度简化方案提出了三种不同的侧移刚度修正方法,分别为固接修正法、铰接修正法和平移修正法。应用等效侧移刚度比法需要首先求解地下结构相应深度位置处自由场地的水平位移差峰值,然后再乘上等效侧移刚度比法的相互作用系数,即可求得该地下结构顶底板水平位移差峰值。最后通过不同工况下(不同截面尺寸、不同地震波输入、不同结构形式)采用该方法与数值模拟分析方法进行比较,验证了该方法的适用性。更多还原

【Abstract】 With the rapid development of the global economic construction, the utilization of the underground space has become a significant research topic in academic field. More and more seismic damages suggest that the underground structures are not necessarily safe, and are even severely damaged in the earthquake. The M8.1 Mexico Earthquake in 1985, the M7.2 Kobe Earthquake in Japan in 1995 and the Wenchuan M8.0 Earthquake in China all caused damages of large number of underground structures. The research of stability of underground structures under earthquake action is one of the hot topics in geotechnical engineering researches, and embodies essential theoretical and practical significance. The subway is an important transportation means in modern cities and is relatively densely populated underground space; therefore the government and society show great concern for its safety and stability. This dissertation studies the subway underground structure, systematically summarizes the main methods of the anti-seismic researches of underground structures and also presents the problems and developing direction; it introduces in detail the basic theory, function and its utilization in the geotechnical engineering seismic resistance of the FLAC3D ;It studies the seismic performance, seismic damage mechanism and practical anti-seismic analytical methods of subway underground structure, the main research achievements are as follows:1. The dissertation applies the constitutive model of concrete damage into the analysis of seismic resistance of underground structures. Based on the concrete damage constitutive theory, it adopts the damage variables determined by evolution equation of concrete damage that is proposed by Mazars, on the basis of D-P constitutive model, it puts forward a damage constitutive model that can consider the comparative derogation of material strength and stiffness after the concrete damage. Based on the user redevelopment environment provided by FLAC3D, it develops the constitutive model using VC++, finally through the numerical simulation test it compares the difference between this model and the D-P model, and it shows the advantages of this damage constitutive model. Using this model, it analyses the damage mechanism of Daikai subway station, and the result well agrees the actual seismic damage, which therefore to some extent verifies the applicability of this damage constitutive model.2. By use of the model developed in this dissertation it successfully simulates the earthquake destruction process of the Daikai subway station and interprets the damage mechanism. The dissertation introduces the general situation of seismic damage in the Dakai subway station, on the basis of FLAC3D it describes the constitutive characteristics of the station by use of concrete damage constitutive model developed in this dissertation, and it analyses the characteristics of dynamic response and the damage process of the station. It establishes an interface element between the structure of the subway station and the surrounding soil layers, and it well simulates the contact, separation and sliding between the structure and the soil in the seismic process. It recognizes that the vertical ground motion increases the vertical stress maximum endured by the underground structure, accelerates the damage of the station interior column, which is the important element of the station damage. The interior column is the anti-seismic weak link in the subway station structure, and the damage mechanism can be explained as under the action of the horizontal and vertical ground motion, the damage of the station structure begins with the interior column, then the damaged column gradually loses the ability of supporting the upper load, and thus the upper plate of the station structure endures great upper soil pressure, the plastic failure takes place between the upper plate and the sidewall, and finally the upper plate and the whole structure collapses.3. It systematically studies the vibration characteristics and the influencing elements of underground structures, summarizes the basic features of the vibration of underground structures, compares the dynamic response characteristics of the underground and ground structures, recognizes that the restraining action makes the vibration characteristics of the underground and ground structures completely different; it specially researches the dynamic soil pressure endured by the underground structure and relative displacement situation of the structure and the soil layers in the earthquake, and discovers changing rules of the dynamic soil pressure and relative displacement of underground structures; It studies the vibration characteristics of underground structures under the action of vertical ground motion, discovers that the vertical stress in the upper and lower plates of the underground structure is much larger than that in the relative depth of the soil; It studies the influences of the overlying soil thickness on the horizontal displacement difference of the upper and lower plates of underground structures, and the result shows that when the thickness of the overlying soil exceeds that of the underground structure, the structural horizontal displacement difference shows linear increasing rules with the thickness of the overlying soil layers; finally it analyzes the influences of the existence of underground structures on the horizontal and vertical acceleration response of the surrounding sites.4. It proposes a practical anti-seismic analytical method-- equivalent lateral displacement stiffness ratio that suits the solution for the upper and lower horizontal displacement difference peak of the underground structures under the action of shear wave. It puts forward three different correction methods of displacement stiffness according to different simplified schemes of displacement stiffness, and they are rigid fixing modified mothod.hinged modified mothod. translation modified mothod. respectively. The application of equivalent lateral displacement stiffness ratio method requires the solution of the horizontal displacement difference peak of the free field in the corresponding depth of underground structure, then it multiplies the interaction coefficient ,and the horizontal displacement difference peak of the upper and lower plates of the underground structures can be obtained. Finally through the comparison between this method and the numerical simulation analytical method under different condition, it verifies the applicability of this method.更多还原