【作者】 孙锐；

【导师】 袁晓铭；

【作者基本信息】 中国地震局工程力学研究所 ， 岩土工程， 2006， 博士

【摘要】 砂土液化是国际上普遍关注的重要问题,我国以往地震液化现象严重,未来灾害威胁很大,其研究一直是工程抗震的前沿课题。本文以液化土层中的地震动(含加速度和位移)为主线研究三方面问题。前两个分别是液化土层对惯性力传递(加速度)及地表位移的影响,是从土层作为上部结构的振动输入媒介及地下结构的变形控制根源的双重角度出发进行研究,属于正演问题。第三个是利用地震记录识别场地液化方法研究,属于液化土层地震动反演问题。本文对国内相关研究进行了系统总结和深入分析,指出了主要缺陷。在此基础上,采用震害调查、实验和数值模拟相对照的方式,对其中关键问题进行了研究,主要工作为:1.通过动三轴系统试验,研究了复杂情况(真实地震荷载作用、非均等固结)下饱和砂土孔压增长模式和规律,提出了一个偏压固结下饱和砂土孔压增量模型和增量型计算公式,建立了不规则动荷载的饱和砂土孔压增长时程简化计算方法,并对方法可靠性进行了验证。2.研究了目前常用土层反应分析方法在用于液化土层地震动时程分析上的局限性,给出了一套土层反应有效应力分析方法,并将该方法与实际地震资料以及振动台实验对比,验证了所提出的数值计算方法可靠性。3.通过地震现场记录分析、振动台实验和理论计算手段,给出了在液化条件下地表加速度反应的现象和特征,包括液化土层对设计反应谱和场地分类影响及规律,特别是液化对加速度反应谱长周期部分影响的认识,提出了液化增量谱和液化修正谱。4.通过现场记录分析、数值模拟和振动台实验手段,研究了地震液化对地表振动位移的影响,提取了液化场地上地表位移特征,提出了液化增量位移谱和液化修正位移谱。5.针对利用地表地震记录进行实时或快速场地液化识别理论研究工作的缺乏,探索了其物理本质,提出了以频率下降率为指标的识别场地液化的新思路,构建了可液化场地双质点体系理论模型,得到了液化引起场地水平自振频率下降率的下限值,以此建立了一套依据强震记录快速识别场地液化的新方法,并与实际资料进行了对比。更多还原

【Abstract】 Sand liquefaction is an important problem by many scientists focusing in the world. In China, the hazard liquefaction-induced is serious in the past and the structures are threatened by earthquake liquefaction in the future. So it is always a forward subject in earthquake engineering.In this paper, three problems are investigated. The first one and the second one is the effect of liquefaction on acceleration and displacement, separately, which is from the view of the soil layer is the media of the vibration and the source of the displacement of the structure. They are forward problems. The third one is the detection method of liquefaction by earthquake records, which is the inverse problem of ground motion.In this paper, the relation studies have been summarized and anglicized and the defects have been found. On this base, the key points have been studied by earthquake investigation, experiment and numerical analysis. The main works are:1. By dynamic triaxial test, the model of pore water pressure under complex consolidation is studied. A new formula which is can be used for calculating the water pressure of saturated sands under anisotropic consolidation is presented and the simplified method of evaluating the pore water pressure time history is established. Their reliability are all tested and verified.2. The limitation of the ground motion analyzing method using for liquefied soil layer is pointed and a effective stress method is presented. This method is tested by real earthquake records and shaking table test.3. By analysis of the earthquake records, shaking table test and numerical analysis, the feature of the liquefied soil motion is found, including the influence of liquefied layer on design response spectrum and site classified and the knowledge of effect of liquefaction on the long period of response spectrum. The liquefaction increment response spectrum and the liquefaction modified response spectrum are presented.4. The liquefaction on the ground dynamic displacement is investigated through earthquake records, shaking table test and numerical analysis. The characteristic of liquefied ground displacement is found and the liquefaction increment displacement response spectrum and liquefaction modified displacement response spectrum are present.5. For the theory shortage of detecting liquefaction from earthquake records, the physical nature is analyzed and a new method of the frequency decrease rate for fast identification of site liquefaction from surface acceleration records is presented. The liquefiable site is simplified as a double-degree-freedom model l and the formula for calculating the reduction of horizontal natural frequency induced by liquefaction is attained. And then the lower limit of frequency decrease rate is derived and based on it, the fast identification method of site liquefaction from surface acceleration records is proposed. The reliability of the method is examined by actual earthquake records更多还原