【作者】 孟凡超；

【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， 2009， 博士

【摘要】 近来的大地震一再表明,地震下软弱土地基和土体的大变形是造成工程结构破坏的重要因素。地基基础和土工结构抗震设计的指导思想也已从传统的强度分析为主逐步向以变形控制为主的设计原则过渡,土体变形分析越来越受到重视。土动力学和岩土工程抗震研究的基本课题之一是研究地震荷载与土动力响应之间的关系。而土体变形与地震动特征间关系的认识是其基础,但目前二者关系的研究上明显缺少两方面的工作:一是对地震波的不对称和不规则性特征的认识尚少;二是地震波的不对称和不规则性对土变形响应影响的认识还不充分,分析方法也有不少缺欠。本文对国内外相关研究进行了系统的总结和深入的分析,指出了主要缺陷和应努力的方向。在此基础上,以实验和实际记录分析为主要手段,对地震荷载与土动力学性能关系中的几个关键问题进行了研究,主要工作和成果如下:1.以饱和土-结构动力相互作用这一典型问题为出发点,借助正弦波输入下小型振动台和地震波输入下大型振动台试验,建立了输入波形、建筑物基底动应力、动孔隙水压力、建筑物沉降和土体永久变形间的联系,发现了它们之间的相互关系及其规律。2.提出了截断比、峰值不对称比、幅值不对称比和作用次数不对称比的概念,通过实际地震记录的统计分析,给出了地震荷载峰值、幅值和作用次数不对称性特征以及波序和荷载类型等不规则性特征的统计规律;3.提出了应变门槛值和有效荷载的概念,通过粘土和砂土两种土类的一系列动三轴试验,明确了地震荷载下土体变形响应的特征,揭示了粘土和砂土应变门槛值与有效荷载下限值的关系,提出了有效荷载的计算公式和推荐值;4.通过系统的动三轴试验,研究了不规则地震荷载与定次数等幅荷载作用下土体变形间的相互关系,提出了一个估计地震荷载下土单元变形的简化方法,给出了地震荷载和土性参数对修正系数的影响规律。更多还原

【Abstract】 In terms of recent catastrophic earthquakes, the earthquake-induced settlement and large deformation of soft subsoils contribute significant effect on the engineering structural damage. The traditional seismic design of structures and foundations has gradually transferred from strength-based philosophies to deformation-controlled philosophies. The analysis of soil deformation has become more and more important.The fundamental task of soil dynamics and geotechnical earthquake engineering is to constitute the relationship between earthquake loading and dynamic stresses in the soil, i.e. the constitution of the relationship between the soil deformation and the parameters of ground motions. However, the current research work seldom considers two aspects, i.e. (1) the acquaintance of the asymmetry and irregularity of seismic waves; (2) the influence of the asymmetry and irregularity of seismic waves on the soil dynamic properties and the corresponding effective analytical methods.In this thesis, the author systematically summarizes and analyzes the previous research and obtained achievement in China and other countries on the subjects and shows the existing limitations and the direction for future research. Based on the laboratory results and the analyses of actual seismic recordings, moreover, some salient points on the conclusive and creative work can be outlined, including:1. In terms of dynamic interaction of saturated soil and structure, using small shaking table tests with sine wave inputting and large shaking table tests with actual seismic wave inputting, the relation of wave shape, dynamic stress under the bases of structure, dynamic pore water pressure, structure settlement and soil permanent deformation has been revealed and developed. The acquaintance of the relationship of soil deformation and ground motion properties comes more and more distinct.2. The concepts of cut-off ratio, peak value asymmetry ratio, amplitude asymmetry ratio and loading number asymmetry ratio are proposed. Through statistical analyses of the actual seismic recordings, the asymmetrical and statistical properties of amplitudes, peak values and loading times of seismic waves, loading types and wave series are presented.3. The concepts of strain threshold and effective loading have been proposed. According to the results of series of dynamic triaxial tests on clays and sands, the dynamic response of soil deformation to seismic loading is discussed herein. The relationship between the strain thresholds and the lower limits of effective loading for clay and sand is proposed. The formula and recommendation values for effective loading are given.4. Through series of dynamic triaxial tests, the soil deformation response under irregular seismic loadings and certain number of uniform-amplitude cyclic loadings has been discussed. A simplified method for evaluating the deformation of soil element under seismic loading and the influence of seismic loading parameters and soil properties on the modified coefficient are presented.更多还原