【摘要】 针对苏州城区典型地层剖面,建立大尺度深软场地的二维精细化非线性有限元分析模型,研究了大地震远场地震动作用于深软场地的设计地震动参数。结果表明:①大地震远场地震动作用时的深软场地地表地震动峰值加速度(PGA)明显大于人工波作用时的地表PGA,输入地震动特性、土介质的横向不均匀性及其非线性,使不同地表位置的PGA存在明显的变异性;②深软场地的地表设计地震动参数max,max和g T值远远大于现行国家规范或标准的取值,且max随地震动水平的提高而增大;③沿土层深度的PGA折减系数,对深度5 m以浅土层可取1,对深度35 m以深土层可取0.65,对中间深度土层可线性内插;④苏州深软场地土的最大剪应变幅值出现在土层深度10 m附近的窄带区域内,且中震、大震水平时,深度10～20 m的土介质处于弹塑性变形到大变形的过渡阶段,对该深度的地下结构,尤其是细长地下结构的抗震不利。对于类似苏州城区的深软场地,应充分考虑远场大地震效应的影响。更多还原

【Abstract】 Based on the typical stratigraphic section in the downtown area of Suzhou City,large-scale refined two-dimensional(2D) finite element(FE) nonlinear analytical models for deep soft site are established.Ground motion design parameters of the deep soft site under far-field large earthquake are investigated.The results indicate that:(1) The peak ground acceleration(PGA) under far-field large earthquake is significantly larger than that under artificial wave.The characteristics of input ground motion as well as inhomogeneity and nonlinearity of ground soils which make PGA at different ground positions have obvious variability.(2) The seismic design parameters,αmax,βmax and Tg T,of the deep soft site are far greater than those according to the existing national code.Moreover,the value of βmax increases as the ground motion level grows.(3) The PGA reduction factor with depth can be obtained as follows: to the soils with depth smaller than 5 m,it is 1.0,while to the soils 35 m in depth,it is 0.65,and it can be obtained by means of the linear interpolation when the soils are between 5 m and 35 m in depth.(4) The maximum shear strain appears at a narrow-band area around 10 m in depth.Under large and medium earthquakes,the soils between 10 and 20 m in depth behave from elasticoplastic deformation to large one,which may bring adverse influence on the underground structures within this band,especially on the slim-lined underground structures.更多还原