典型模型瑞雷波椭圆率曲线形态特征分析

The analysis of rayleigh wave ellipticity for typical models

瑞雷波椭圆率(χ)被定义为瑞雷波椭圆极化质点运动水平与垂直轴之间的比率。在工程中计算瑞雷波椭圆率的简单方法,是求取微动信号水平与垂直振幅谱比值。基于微动的H/V技术已经越来越流行,并且广泛用于估计场地的基本周期。H/V曲线与瑞雷波频散曲线联合使用,在反演地层剪切波速、岩土地层划分、孤石探测等岩土工程勘察中均有较成功的案例。微动H/V技术理论尚不完备,目前主要有两个前沿理论研究方向:利用整个环境振动波场来描述H/V曲线和瑞雷波椭圆率分析。这里主要研究瑞雷波椭圆率,通过对与岩土工程相关的几种典型模型进行数值计算,更深入地分析瑞雷波椭圆率曲线的特性。对3个有代表性的工程场地的6个钻孔进行了微动测试,得出微动H/V谱曲线与理论瑞雷波椭圆率曲线具有相同的趋势,但由于Love及体波的影响,两者曲线形态在细节部位表现并不一致。

Rayleigh wave ellipticity indicates the ratio between the horizontal and vertical axes of the Rayleigh waves.In engineering,the Rayleigh wave ellipticity is simply calculated by the spectral ratio between the horizontal and vertical components recorded by a single seismic sensor.In the last decade,the H/V of the microtremor is more popular especially in the estimation of the site predominant frequency.The H/V curve is successfully used together with Rayleigh dispersion curve in the geotechnical engineering investigation,such as the inversion of shear wave velocity,geotechnical stratigraphic classification and boulder detection etc.The theory of the H/V is still not well understand.At present,there are two main leading research directions:Rayleigh wave ellipticity analysis and H/V curve based on the whole environmental vibration wave field.This paper is focused on the former.The characters of Rayleigh wave ellipticity are analyzed deeply through several typical models related to geotechnical engineering.For application the microtremor data is collected at the same location of six boreholes from three typical engineering sites.The H/V curves are calculated and analyzed.In conclusion the H/V curve has the same tendency of the Rayleigh wave ellipticity.The difference in the detail parts is caused by the Love wave and body wave.