土层剪切波速测试中的不确定性对场地地震动参数的影响分析——以Ⅲ类场地为例

Analysis of Ground Motion Parameters Impact on Soil Shear Wave Velocity at Different Depths——A Case of Site Class Ⅲ

本文选取山东地区2个Ⅲ类场地的工程地质勘探及土层剪切波速等资料,将土层厚度按5个深度段,每个分段给出了4个土层剪切波速的改变量,通过改变不同深度段土层剪切波速,建立了19种土层地震反应分析模型,分析了不同深度段,不同概率水平下土层剪切波速的变化对场地地震动参数的影响。研究表明,不同深度段土层剪切波速的变化对场地地震动参数的影响有差异。具体表现为,土层剪切波速的改变在1—10m、11—40m和地震输入界面处三个深度段对地震动加速度峰值影响较大;其中,41—70m和71—100m两个深度段剪切波速的改变对地震动加速度峰值影响小;在土层深度1—10m时,剪切波速降低,峰值变大,剪切波速的改变与峰值的改变呈负相关;在其它深度段,剪切波速降低,峰值变小,剪切波速的改变与峰值的改变呈正相关。剪切波速的改变在1—10m和11—40m两个深度段对地震加速度反应谱影响较大;在41—70m、71—100m和地震输入界面三个深度段对地震加速度反应谱影响很小。

We selected data of engineering geological exploration and soil shear wave velocity from two class Ⅲ sites in Shandong,and divided the depth of soil thickness into five segments,in which each segment is given four values of soil shear wave velocity.By changing the soil shear wave velocity at different depth,we established 19 kinds of soil seismic response analysis models,and analyzed influence on segments at different depths and different probability levels change on soil shear wave velocity of ground motion parameters.Our results show that the change soil shear wave velocity at different depth has different impact on ground motion parameters.Particularly,changes in soil shear wave velocity at 1-10m,11-40m and interface where seismic wave input have the greater influence on peak ground acceleration.Whereas,the changes of shear wave velocity at 41-70m and 71-100m depth have the less influence on the peak ground acceleration.In soil at depth 1-10m,with the decrease of shear wave velocity the peak acceleration increases,and vice versa at the other depths.Changes of shear wave velocity have great influence on acceleration response spectra at 1-10m and 11-40m depth,and small influence at 41-70m and 71-100m depth.