摘要
通过在一工程场地进行的地脉动台阵观测和速度结构反演,从地脉动观测系统、面波频散曲线的提取和反演方法等关键环节探讨反演浅层速度结构的可能性。研究结果表明:(1)用空间自相关法提取瑞利波频散曲线,进而借助基于遗传算法的混合智能算法反演的场地浅部剪切波速度结构与钻孔法测试结果的平均相对误差在20%左右。(2)覆盖层平均波速的结果计算与频率–波数法的分析结果几乎完全相同,但频率–波数法对上部20m土层只得到一平均波速。(3)方法精度与目前国际同类研究——表面波谱分析方法的精度基本相当。在岩土工程和地震工程领域,波速结构测试最直接的目的是评价场地土层的动力性能。进一步从对地震地表反应影响的角度,用一维土层的等效线性化方法分析地脉动台阵方法的有效性。分析结果表明,使用地脉动反演波速结构模型的误差远小于仅用覆盖层平均等效波速的单层模型对地表反应谱影响。仅用一平均等效波速进行抗震设计是不够的,探测浅层速度结构是非常必要的,地脉动台阵方法有潜力作为探测场地浅部剪切波速度结构的一种有效手段。
By the microtremors array observation and velocity structure inversion in the field of an engineering project, the accuracy of microtremors array methods（MAM） for exploring the detailed shallow velocity structure is studied with observation system, dispersion curve extraction and inversion methods. The shallow S-wave velocity structure is inversed by the hybrid method of genetic algorithm（GA） and simplex algorithm（SA） from the surface wave dispersion curve, which is inferred by the spatial auto-correlation method（SAC） from microtremors array records. The studies show that the relative average error of each layer is about 20% compared with that detected by borehole method. The average velocity obtained by SAC method and frequency wave-number method（F-K） is almost the same. However, F-K method only gives an average velocity for the upper 20-meter layer. The accuracy is compared with that of spectral analysis of surface wave（SASW） method. In the fields of geotechnical engineering and earthquake engineering, the direct goal of velocity structure exploration is site dynamic characterization. From the viewpoint of site seismic responses, the accuracy of MAM is further validated by 1D equivalent linearized analysis. The analytical results show that the difference between the response spectra from inversed velocity structure and that measured in borehole is really acceptable, whereas that for the simplified single layer model with the average velocity is quite large. The study suggests that it is not a good idea in seismic design to characterize site condition only by the average velocity; and the MAM has the potential to be an effective method for the shallow velocity structure exploration.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2006年第8期1683-1690,共8页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(50378032)
地震科学联合基金资助项目(604034)
关键词
地震工程
剪切波速结构
浅部
地脉动
台阵观测
场地反应
earthquake engineering
S-wave velocity structure
shallow layer
microtremors
array observation
site response
