Abstract: Based on analysis of the shear wave velocity data of 823 boles from the northern,eastern,southern,northeastern and northwestern areas of China,we studied the difference of the equivalent shear wave velocities calculated with the soil-and-rock depths of 20m and 30m,respectively.We also discussed the features and differences among the Chinese,American and European seismic regulations in site classification using the parameter of equivalent shear wave velocities of boles.Our results indicated that:① The equivalent shear wave velocity will increase about 10 to 60m/s when we increase the calculation depth of soil-and-rock from 20m to 30m.The average increase is about 24m/s.② Comparing with the American and European seismic regulations,the current Chinese seismic regulation(GB 50011-2001)requires the information of the equivalent shear wave velocities calculated with the soil-and-rock depths of 20m,as well as the depth of the overburden in the site when classifying the site.However,it is usually difficult to obtain the usable overburden depth in many engineering sites to serve the site classification.Therefore,it is necessary for us to use for reference of American and European seismic regulations to increase the depth of soil-and-rock when calculating the equivalent shear wave velocity so as to get a more reliable parameter to serve for the site classification.

Key words: equivalent shear wave velocity, depth of soil-and-rock for calculation, site classification

摘要： 根据中国华北、华东、华南、东北和西北等地918个实测钻孔资料的计算统计,探讨了工程场地分类中等效剪切波速计算深度取值20m和30m的实际差别,并对中国、美国、欧洲现有规范利用等效剪切波速进行场地类别划分的方法特点和具体指标进行了对比讨论。结果表明:1)计算深度由20m增加至30m时,钻孔等效剪切波速值的增大范围约为15～50m/s,平均增加值为25m/s;2)与欧美规范相比,中国现行规范(GB50011-2001)在划分场地类别时要求同时考虑20m计算深度的等效剪切波速值和覆盖层厚度,而在许多实际工程中,因较准确的覆盖层厚度不易获取而难以具体进行场地分类。因此,有必要借鉴欧美规范,通过增大等效剪切波速的计算深度至30m来强化该指标在场地类别判定中的作用。

关键词: 等效剪切波速, 计算深度, 场地分类