脉冲型地震动作用下典型珊瑚岛礁的场地放大研究

Seismic response analysis of coral reef under pulse-like ground motions

为研究南海地区珊瑚岛礁场地对地震动的放大作用特征,基于南海珊瑚岛礁几个代表性场地钻孔资料和60条近断层脉冲型强震记录,结合强震数据和土层地震反应分析结果讨论了地震动幅值水平和场地条件对场地放大的影响。根据地貌单元特性、地层岩性、成因和分布规律,得到4类工程地质场地,建立了一维土层地震反应分析模型并选取了土体动力参数,讨论了其在脉冲型地震动作用下地震反应特征。结果表明:从土层剪切波速来看珊瑚礁场地属于我国国家《建筑抗震设计规范》中的Ⅱ类场地;珊瑚礁场地对脉冲型地震动的放大倍数在1.6~2.4之间,放大明显的周期在0.2~0.8s之间。另外,对珊瑚礁礁坪区、泻湖区、沙洲区和灰沙岛区4类场地的地震反应分析表明:在脉冲型地震动作用下沙洲区场地放大倍数小于其他区;灰沙岛区在周期为0.3s左右时场地放大倍数明显大于其他区。研究结果整体反映了珊瑚礁场地对脉冲型地震动的场地放大特征,可对珊瑚礁的开发建设提供参考。

In order to study the site effect of coral reef in the South China Sea under pulse-like ground motion, several representative soil drilling data and 60 near-fault pulse-like ground motions were selected in this paper, based on the seismic data and equivalent linearization analysis method, the effect of PGA value and site condition on amplification were discussed. The coral reefs are divided into four types, and the physical, mechanical parameters and dynamic nonlinear parameter model were established. The seismic response of coral reef site under pulse-like ground motions were discussed. Results show that ： According to the soil shear wave velocity, the coral reef site can be classified as category Ⅱ in the Code for seismic design of building in China ; the amplification ratio of the ground motion is 1.6 - 2.4, and the obvious period of for amplification is between 0.2 - 0.8 s. In addition, analysis of seismic response of the reef flat zone, lagoon zone, reef crest zone and sand island zone of coral reef indicate ： The amplification under pulse-like ground motions of reef crest zone is smaller than the other zone ; the amplification of sand island zone is greater than the other zone at the period around 0.3 s. The results of this study reflect the site amplification characteristics of the ground motion on the coral reef, which could provide reference for the development and construction of coral reef sites.