【作者】 刘林超；

【导师】 杨骁；

【作者基本信息】 上海大学 ， 固体力学， 2010， 博士

【摘要】 桩基由于具有抗震性能好、沉降量小、承载力高、以及能适应各种复杂地质条件等优点而被作为一种重要的深基础形式广泛应用于海洋平台、桥梁工程、铁路公路工程、大型厂房、高层建筑等众多工程领域。在动荷载作用下桩基础的承载力取决于桩的工作性能,而桩的工作性能是桩与桩周土之间动力相互作用的结果;同时,桩—土动力相互作用伴随有能量在土体中的传播和耗散,进而引起相邻桩的振动。所以,研究桩—土动力相互作用问题是研究单桩和群桩振动特性以及桩—土—结构动力相互作用的关键和基础。饱和土中孔隙水的流动特性以及桩基与土体的不同渗透率,饱和土—桩相互作用与单相土—桩相互作用的力学行为,尤其是动力学行为在性态上存在很大差异。将固、液、气三相介质组成的土体视为单相介质与实际的工程地质性能不符,将利用单相土中桩基振动特性的理论和方法研究饱和土中桩基振动特性以及饱和土—桩—上部结构耦合动力响应势必造成一定的差异。本文将土体视为饱和两相多孔介质,运用多孔介质理论描述饱和土体的宏观力学性能,将Novak平面应变模型推广到饱和土介质,借助于势函数得到了饱和土层的纵横向动力阻抗,在Novak薄层法的基础上对饱和土中单桩的纵横向振动进行了研究;将单桩动力阻抗和动力响应的研究推广到群桩,基于群桩动力相互作用因子的定义,分别对饱和土中桩—桩竖直和水平动力相互作用因子进行了研究,并分析了主要桩土力学参数的影响;运用基于动力相互作用因子的叠加原理对考饱和土中群桩的竖向和水平动力响应进行了分析,并以3×3桩为例对群桩动力阻抗的主要影响参数进行了分析,发展了一种分析饱和土中桩—桩动力相互作用和群桩动力阻抗的新理论。同时,将上部结构视为梁单元模型,考虑饱和土—桩—上部结构的耦合作用,研究了简谐SH地震波作用下的饱和土—桩—上部结构的动力相互作用问题,对建筑结构的抗震设计提供了理论基础和参考依据。更多还原

【Abstract】 With the advantages of good seismic performance, small settlement, large capacity and broad applicability to complicated geological conditions, pile as an important deep foundation has been widely used in many engineering fields, including offshore platforms, bridges, railways and highways, large-scale plants, high-rise buildings and so on. The carrying capacity of a pile under dynamic load is related to its field performance, which is dependent on the interaction between the pile and surrounding soils. The pile-soil dynamic interaction goes along with the propagation and dissipation of energy in soil, and leads to the vibration of adjacent piles. Therefore, the study on pile-soil dynamic interaction is the key issue for studying the dynamic properties of single pile and pile groups in soil, and the dynamic interaction of pile-soil-structure.The mechanical properties, especial dynamic behaviors of a pile in saturated soil and single-phase soil make a great difference, due to the flow quality of pore water in saturated soil and the difference permeability of the soil and the pile. It is inconsistent with the actual performance of engineering geology for assuming the soil which consists of soil, fluid and gas as single phase medium. The assumption will certainly result in discrepancies when applying the theories of dynamic performances of pile in single phase soil to the pile and piles in saturated soil and the dynamic interaction of the saturated soil-pile-structure.In this study, the soil around the pile is regarded as saturated porous medium, the macro-mechanical properties of saturated soil is described by the theory of porous medium. Appling the Novak plain strain model to saturated soil, the vertical and horizontal dynamic impedance of soil layer is obtained using potential functions, and the vertical and horizontal vibration of single pile in saturated soil are investigated by means of the Novak layer method. The study of dynamic impedance and response of single pile is extended to pile groups in saturated soil. The vertical and horizontal dynamic interaction factors and the effects of main mechanical parameters of pile and soil are investigated. With the principle of superstition based on interaction factor, the vertical and horizontal dynamic response of pile groups in saturated soil is analyzed; the influences of main parameters on dynamic impedance is investigated taking the 3×3 pile group as an example. A new theory for studying the pile-pile dynamic interaction and dynamic impedance of pile groups in saturated soil is proposed. The saturated soil-pile-structure dynamic interaction under harmonic SH wave is also investigated by regarding the superstructure as a beam model and considering the coupling effect of soil-pile-structure. Some theoretical foundation and reference for seismic design of building are provided.更多还原