【作者】 黄群贤；

【导师】 林建华；

【作者基本信息】 华侨大学 ， 结构工程， 2003， 硕士

【摘要】 地震过程中由于饱和砂土液化诱发的小坡度地面侧向永久位移即地面大位移对结构的破坏，是液化区公路、铁路、桥梁、码头、堤坝、房屋、地下结构与生命线工程震害的主要形式之一，近十几年来，人们越来越重视对这种新的液化破坏形式的研究。由于砂土液化诱发地面大位移机理比较复杂，且对其研究历史较短，目前对这个问题的研究还不够深入。本文主要做了以下工作： 1、本文总结了以往地面大位移计算方法的不足，提出了计算砂土液化诱发地面大位移的一种新方法。通过对土体进行非线性地震反应分析，引入地震过程中饱和砂层中孔隙水压力生成的经验公式，利用这一公式在各时段内对土的抗剪强度进行修正，假定每一时段内土的应力-应变关系为刚塑性，求出该时段内的地面加速度时程和屈服加速度时程，然后根据Newmark刚性滑块的基本原理，计算地震过程中由液化产生的地面侧移值，并对影响地面大位移的各种可能因素进行了详细的研究。计算结果表明：与经验方法相比较，本文提出的计算地面大位移的方法在物理机制上更加合理，能够较真实地揭示地面大位移产生的规律，且计算结果与宏观震害现象十分吻合，具有较强的工程适用性。 2、本文运用ANSYS有限元分析软件，建立桩基在侧向力作用下的有限元计算模型，并通过工程算例验证该方法是正确的、可行的，在选取合理的单元大小，其计算结果与理论结果吻合较好；利用该计算模型考虑桩土共同工作的非线性关系，对土弹簧单元施加侧向位移模拟在液化侧扩地基中土体产生的侧向位移，对液化侧扩地基中的桩进行非线性有限元分析。计算结果表明地基的侧向位移是与液化有关的桩基震害的主要原因之一，在软硬交界处桩可能承受了超出桩本身极限抗弯能力的弯矩，容易发生弯剪破坏，在有液化侧扩地基中桩基的设计不能仅考虑上部结构震动的影响，地基的水平侧向位移对桩基的影响不容忽视。所得结果对今后桩基的抗震设计具有一定的指导意义。 3、本文根据地震液化诱发地面大位移产生的机理，针对自由场地、已建结构场地以及地面大位移对桩基破坏的特点，归纳总结了防治地面大位移的措施。更多还原

【Abstract】 Catastrophic damages to structure can be made by lateral permanent displacement, namely large ground displacement, on gently sloping ground induced by liquefaction of saturated soil deposits during earthquake, which is the main type of seismic damages of highways , railways, bridges, docks, embankments, buildings, underground structures and lifeline engineering in liquefied area. In recent ten years, studies on the new type of failure made by liquefaction have been carried out. Because of the complex mechanism and the limited research, progress on this subject is quite limited. The paper is made up of three aspects:1 , In this paper the disadvantages of calculation methods of large ground displacement are discussed, and the new method used to calculate the large ground displacement is presented. Nonlinear earthquake respond analysis of soil is carried out to obtain ground acceleration and yield acceleration time history, in which the law of pore pressure in saturated sand is used to revise the yield strength of soil and the strain-stress relationship of soil is assumed to be rigid plastic in every time-internal. Appling the model of Newmark’s rigid slide block, the lateral displacement induced by liquefaction during earthquake is calculated and the possible factors which may influence the large ground displacement are well studied. The numerical results show that the method presented is more reasonable in physical mechanism than empirical methods, which can authentically disclose the mechanism of the large ground displacement and coincide with macroscopic earthquake damages.2, Using ANSYS, a finite element analysis model is established to deal with pile-soil interaction under lateral load, and the model is proved to be correct and realizable. With the reasonable size of element, the results can well coincide with theoretical results. Using the model, nonlinear finite analysis of pile in lateral spreading ground is carried out, in which the nonlinear relationship of pile-soil interaction is considered and lateral displacement is subjected to soil springs to simulate the ground displacement in lateral spreading ground. The numerical results show that the lateral ground displacement is one of factors that cause pile failures in liquefied ground. At the soft-hard interface, pile may overbear the ultimate moment which leads to bending and shearing failures. Therefore, except the effect of large inertial loads from superstructure, the influence of the lateral ground displacement onpile foundation cannot be neglected in a seismic design of pile foundation in lateral spreading ground.3. According to the mechanism of large ground displacement, different measures of ground improvement against large ground displacement suited to different conditions are concluded.更多还原