基岩面埋深是公路工程建设中的重要参考依据.本文通过福建地区两个探测实例,研究了微动H/V谱比法探测基岩面埋深的方法技术,介绍了微动H/V(Horizontal to Vertical)谱比法提取基岩面埋深的方法原理.首先对微动单个三分量检波器采集地震记录进行处理和分析,获取了测点的峰值频率F0.在钻孔较多的情况下,可根据钻孔的中风化岩深度与峰值频率F0的幂函数拟合,得到了该区的经验参数a和b,从而可以计算整个测区每个测点的中风化岩深度三维分布.在钻孔较少的情况下,可根据测区内部分钻孔的孔内剪切波值计算该区的覆盖层平均横波速度,进而根据经验公式计算覆盖层厚度和基岩面三维埋深分布.两个探测实例研究结果表明:微动H/V谱比法是一种快速获取公路工程三维基岩面的方法,在一定条件下,相对误差能够控制在5％左右,能够满足工程勘察的需求.微动谱比法具有简便性和易操作性,点位可随机布置,几乎不受场地条件限制,能够取得较好的地质效果,可推广应用.
Research and Application of Microtremor H/V Spectral Ratio Method for Extracting the Depth of Bedrock Surface
The burial depth of the bedrock surface is an important reference basis in highway engineering construction.This article studies the microtremor H/V(horizontal to vertical)spectral ratio method to detect the depth of bedrock surface through two detection examples in Fujian region,and introduces the principle when using the microtremor H/V spectral ratio method to extract the depth of bedrock surface.Firstly,the seismic records collected by a single three component microtremor detector were processed and analyzed,and the frequency peak F0 of the measurement point was obtained.In the case of a large number of boreholes,the empirical parameters a and b of the area were obtained by fitting the power function of the depth of moderately weathered rock and the peak frequency F0 of the boreholes.The three-dimensional distribution of the depth of moderately weathered rock at each measure-ment point in the entire measurement area were calculated.In the case of fewer boreholes,the average shear wave velocity of the covering layer in the measurement area were calculated based on the shear wave values in some boreholes,and then the thickness of the covering layer and the three-dimensional depth distribution of the bedrock surface were calculated based on empirical formulas.The results of two detection examples indicate that the micro-tremor H/V spectral ratio method is an efficient method to obtain the three-dimensional bed-rock surface of highway engineering.Under certain conditions,the relative error can be con-trolled within about 5％,which can meet the needs of engineering exploration.With its sim-ple and easy operation,the microtremor spectrum ratio method,with randomly arranged points that are almost not limited by site conditions,can achieve good geological effects and has wide applications.
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维普
