不同地震动强度下珊瑚礁砂地基中桩-土-结构地震响应试验研究

Seismic response of pile-soil-structure in coral sand under different earthquake intensities

珊瑚礁砂在地震作用下的场地响应受其特殊的工程性质影响。为揭示珊瑚砂场地桩基-地基-上部结构在地震作用下的动力响应特性,开展了不同地震动强度下珊瑚砂地基上3层框架结构群桩基础的振动台模型试验,对地基土和结构物的动力响应进行测试与分析,同时与可液化福建砂场地进行对比研究。结果表明:0.1g正弦波激励下,两种砂模型地基内各处超孔压比均远小于1,模型地基未发生液化;0.2g正弦波激励下,两种砂模型地基发生液化,珊瑚砂场地液化程度小于福建砂场地,液化后的珊瑚砂场地模型地基相比福建砂场地仍具有一定的剪切传递能力和刚度。0.1g和0.2g振动强度下珊瑚砂场地建筑物沉降、水平位移和立柱动弯矩相比福建砂场地较小。不同振动强度下桩基础出现动弯矩峰值的位置不同。

The dynamic field response to earthquake in the coral sand is affected by its special engineering properties.In order to reveal the seismic response characteristics of the pile-soil-superstructure in the coral sand site,the shaking table tests of pile groups with three-storey frame structure in coral sand under different earthquake intensities are carried out.The dynamic responses to soil and structure are analyzed and compared with those in the liquefied quartz sand of Fujian.The results show that the excess pore water pressure ratios in both coral and quartz sands are far less than 1 under 0.1 g seismic intensity,demonstrating that no liquefaction occurs in both sites.However,both coral and quartz sands are liquefied under 0.2 g seismic intensity,and the liquefaction degree of coral sand is less than that of quartz sand.Compared with the quartz sand site,the coral sand site still has some shear strength and stiffness after the liquefaction.The settlement,horizontal displacement and column bending moment of coral sand site under 0.1 g and 0.2 g seismic intensities are smaller than those of quartz sand site.The position of peak bending moment of pile foundation under different seismic intensities is not the same.