砂土液化夹层既会造成地基失效破坏，又会对上部建筑起到减震作用，而覆盖层可以减小建筑沉降，却会放大地震作用，因此，有必要探讨结构与土相互作用下液化夹层和覆盖层对建筑的隔震耦合影响。基于Biot两相饱和多孔介质动力耦合理论，采用有限元和有限差分耦合动力分析方法，分析不同地震强度、砂土密实度D_r和液化层厚深比K（考虑液化夹层和覆盖层耦合作用）对上部结构隔震的影响。结果表明：结构加速度反应谱比随震动强度增加先减小后趋于稳定，当震动强度超过某阈值时，液化层隔震效果不再增加；松砂（D_r=30%）的隔震效果优于中密砂（D_r=50%）和密砂（D_r=70%），但会产生不可忽略的沉降危害；密砂虽然能更好地抑制建筑沉降量，但在短周期内会起到加震作用；考虑覆盖层和液化层的耦合作用，发现K值在0.3~0.5区间内时，既能减小建筑沉降，又能起到减隔震作用。

A sandy soil liquefaction interlayer can cause both foundation failure and damping effects on the superstructure, while the overburden would reduce building settlement but increase seismic effects. Therefore, it is necessary to consider the seismic coupling effects of the liquefied interlayer and the overburden on the building under the structure-soil interaction. Based on the Biot two-phase saturated porous medium dynamic coupling theory, the effects of seismic intensity, sand compactness D_r and liquefied layer thickness-to-depth ratio K (considering the coupling effect of liquefied interlayer and overburden) on the seismic isolation of the superstructure are analysed using finite element and finite difference coupled dynamic analysis methods. The results show that the structural acceleration spectrum ratio first decreases and then stabilises with increasing seismic intensity, and the damping effect of the liquefied layer no longer increases when the seismic intensity exceeds a certain threshold; the damping effect of loose sand (D_r=30%) is better than that of medium-density sand (D_r=50%) and dense sand (D_r=70%), but it would cause a non-negligible settlement hazard, while dense sand, although it will better suppress the settlement amount of the building, would lead to amplification of vibration; considering the coupling effect of overburden and liquefied layer, it is found that there is a K-value interval (0.3<K<0.5), which can both reduce building settlement and act as shock absorber.

TU435

土木工程防灾减灾湖北省引智创新示范基地（2021EJD026）