深厚软土场地中透镜体对上部结构地震响应的影响

Effect of lenticle in deep soft site on seismic response of structures

工程场地中透镜体对地震动具有重要影响,但目前对该问题的研究比较少,尤其是深厚软土场地中的透镜体问题还鲜有研究。本文采用有限元-间接边界元耦合法,建立非线性土-结构动力相互作用模型,并对方法计算精度进行了验证。论文首先比较了弹性基岩模型和刚性基岩模型的差别,建议采用更接近实际的弹性基岩模型研究深厚软土场地中的透镜体问题。然后在考虑场地土体和透镜体介质非线性的基础上,系统地研究了深厚软土场地中透镜体宽度、厚度和埋深对上部结构地震响应的层间位移角、加速度及基底剪力的影响。研究表明,透镜体的存在可能会明显改变上部结构的动力响应,上部结构的动力响应可能会明显放大。透镜体宽度、厚度和埋深对结构动力响应均有很大影响。

A lenticle existing in engineering site has significant effect on the earthquake ground motion, however,there is few studies in literature up to now, and it is rare to see the study especially for a lenticel in deep soft site.This paper proposes a finite element and indirect boundary element （FEM-IBEM） coupled method for the nonlineardynamic soil-structure interaction model, and validates the accuracy of the method. First, the paper makes compar-ison between the models with rigid bedrock and that with elastic bedrock, and suggests to use the model with elasticbedrock for the deep soft site. The paper then systematically investigates the effect of width, thickness, embeddeddepth of a lenticle in deep soft site on the story drift, floor acceleration and base shear force of the structure by con-sidering the nonlinearity of the soil and lenticle. It＇ s shown that the lenticle has evident influence on the dynamicresponse of the structure and the response may be amplified significantly. The lenticle width, thickness and embed-ded depth all have a great influence on the response of structure.