回填土场地强震动性质讨论

Discussion on the properties of strong ground motion on backfill sites

本文旨在讨论位于回填土场地上及回填土场地深挖基坑内的强震动观测仪所获得地震动是否是真实自由场地震动,若不是,其影响如何?结合回填土场地的强震动观测台站建设的实际情形,建立了回填土场地和回填土场地深挖基坑的有限元分析模型,基于集中质量显式动力有限元数值模拟方法,分析了回填土的波速和厚度、基坑尺寸对自由场地震动的影响.同时,提出了通过用重塑土置换回填土以降低回填土对自由场地震动影响的措施,并对重塑土置换回填土的效果进行了数值模拟分析.结果表明:回填土上和回填土深挖基坑内的地震动峰值和反应谱值与原始场地的均有明显的差异,随着回填土厚度和基坑深度的增加,其差异越大;通过重塑土置换回填土可以减小回填土对场地地震动的影响.本文所得关于回填土、基坑和重塑土的影响规律可为回填土场地上强震动观测结果的合理利用以及强震动观测台站建设提供依据.

This paper aims to quantitatively study the impact of backfill and foundation pits on free-field ground motion. A finite element model for this issue is established based on the actual situation. Using the numerical simulation method of the concentrated mass explicit dynamic finite element, we analyze the effects of the shear wave velocity, the thickness of backfill soil, and the size of foundation pit on free-field ground motion. At the same time, the remodeling soil analysis models are established to analyze the effect of remolded soil on free-field ground motion. The results show that both the backfill soil and foundation pits can affect the free-field ground motion peaks and the values of response spectrum significantly. With the increase of the thickness of backfill soil and the depth of foundation pits, the influence is more noticeable. Replacing the backfill by remolding soil can reduce the effect of the backfill on the free field. The results can provide a basis for the rational use of the strong ground motion records on the backfill site and the construction of the strong ground motion observation stations.