软夹层和硬夹层对地表地震动特性的影响

Effects of Soft and Hard Interlayers on Ground Motion Characteristics

摘要:

利用日本KIK台网地表和井下地震记录验证了一维等效线性化土层地震反应程序，结果表明在土体小变形范围内，对于刚度递增型场地，程序计算结果与实际相符；而对于含软夹层或硬夹层的场地，程序计算结果与实际相差较大。据此，本文提出了一种研究软夹层和硬夹层对地表地震动影响的方法。为得到参照标准，将真实土层剖面中的夹层替换为正常土层，以满足刚度递增条件，采用土层地震反应程序计算在井下地震记录激励下的地表反应。将其与该场地地表实际地震记录进行对比分析，可得到软夹层和硬夹层对地表地震动的影响结论。本文对几个典型场地进行计算分析后得到如下结论：软夹层与硬夹层对地表地震动的影响是一致的；当夹层处于覆盖层上部时对高频地震动有较强的放大作用；当夹层处于覆盖层下部时对高频地震动有隔震作用。

Abstract:

The program for one-dimensional equivalent linear soil seismic response is verified using the underground and surface seismic records of the KiK network in Japan.The results show that，in the range of small soil deformations，the calculated ground motions are consistent with the actual motions for the sites where the stiffness of soil layers increase with depth，but not for the sites with soft or hard interlayers.Accordingly，this paper presents a method to study the effects of soft and hard interlayers on ground motions.As a reference，the interlayer is replaced by a normal soil layer to meet the condition of increasing stiffness.Then，the surface seismic response excited by the actual underground motions is computed using the program.Comparing the computed motions and the actual motions on the surface，conclusions can be drawn.Some representative sites are studied in this paper.The results show that the effects of soft and hard interlayers on ground motions are consistent；there is an amplification of high-frequency motions if the interlayer is shallow，but there is an action of seismic isolation to high-frequency motions if the interlayer is deep.