基于软土场地实测记录的三种土层地震反应分析方法可靠性研究

Reliability comparison of three kinds of seismic response analysis methods for soil layers in soft soil site

软土场地地震反应计算分析方法是公认难题。以日本KiK-net强震观测台网中所有软土场地井下记录为样本,对传统等效线性化方法SHAKE2000、时域非线性方法DEEPSOIL和频率一致等效线性化方法SOILQUAKE三者在软土场地地震反应分析计算中的可靠性进行对比检验。检验工况包括KiK-net井下台网中地表峰值加速度不小于0.05 g的所有水平软土场地的总计309台次的加速度记录,涉及24个台站,土层厚度28 m～240 m,地表峰值加速度范围0.050 g～0.580 g。对比结果表明:烈度6度和7度偏下(地表PGA在0.12 g以下)的较弱地震动下,对三类、四类和巨厚场地,SOILQUAKE、SHAKE2000和DEEPSOIL三个方法计算结果相差不大,与实际记录较为接近,皆可采用;烈度7度中上以上(地表PGA在0.12 g以上)的较强地震动下,无论是三类、四类和巨厚场地,DEEPSOIL和SHAKE2000计算出的地表PGA和反应谱较实际记录偏小,且随地震动强度增加差距急剧增大,甚至小于井下输入,而SOILQUAKE计算出结果与实际记录基本相当,可体现出软土场地放大作用,也证明了频率一致等效线性化方法的有效性。

Seismic response analysis of soft soil site is a difficuh problem in seismic response analysis of soil layer. Using the 309 times records of underground seismic observation of Japanese KiK-net strong motion of network data- base, the three methods for calculating one-dimensional earthquake response analysis of soil layers in soft sites are verified. One of the methods is SOILQUAKE16 recently developed and the others are SHAKE2000 and DEEP- SOILS. 0 used worldwide. The test conditions include seismic acceleration records of all soft soit sites with a surface peak acceleration of not less than 0.05 g in the KiK-net network. The peak ground acceleration of these records belonging to 24 stations range from 0.05 g to 0. 580 g. The results indicate that there are similar accuracies of the calculated values by the above three methods under weak ground motion and the calculated values are near to the measured values both in the peak ground acceleration and surface acceleration response spectra. In the moderate and strong ground motion, however, the calculated values by SHAKE2000 and DEEPSOILS. 0 are obviously lower than the measured values and the gap between the calculated ones and the measured ones increase with the increasing of ground motion intensity. By the contrast, the result of peakground acceleration and surface acceleration response spectra by SOILQUAKE16 is close to the measured values, and can reflect the amplification effect of seismic ground motion in soft sites.