基于微动H/V谱比法的土石分界面探测研究——以济南中心城区为例

土石分界面对城市抗震设防和地下工程建设具有重要意义.城市中复杂的干扰限制了常规地球物理勘探方法的使用,本文选用环境友好且抗干扰能力强的微动H/V谱比法对济南中心城区的土石分界面展开研究.在济南中心城区开展三分量微动测量,得到了400多个测点的微动数据,计算了对应的H/V谱比曲线.将得到的H/V曲线划分成单峰、宽峰、双峰和无峰四种类型,分析了不同类型曲线与地质结构的关系.根据基岩性质不同,将研究区的基岩划分为灰岩和岩浆岩两种类型,总结出了基岩为灰岩时的深度-频率关系式,同时发现当基岩为岩浆岩时无法得到可靠的关系式.根据关系式计算得到了济南部分测线的土石分界面深度分布,另外,关系式的计算结果与钻孔资料十分吻合,能满足工程探测的精度要求.本方法为在城市强干扰环境中确定土石分界面深度提供了快速准确的解决方案.

Detection of the soil-rock interface based on microtremor H/V spectral ratio method: a case study of the Jinan urban area

The soil-rock interface plays an important role in urban earthquake resistance and engineering construction of the underground. The various interference in the city limits the use of traditional geophysical exploration methods. This paper presents a study on the soil-rock interface of the Jinan urban area using the microtremor H/V spectral ratio method,which is environmental friendly and has strong anti-interference ability. Microtremor measurement was carried out in the downtown area of Jinan,and the microtremor signals of more than 400 measuring points were obtained,and the corresponding H/V spectral ratio curves were calculated. These H/V curves are divided into four types:single peak,broad peak,double peak and flat curves. The relationship between different types of curves and geological structure are analyzed. The bedrocks of the study area are divided into two types according to its characters,limestone and magmatic rock. The depth-frequency relationship of bedrock limestone is summarized. It is also found that when the bedrock is magmatic rock,such a relationship cannot be obtained. According to this relationship,the depth of the soil-rock interface of some lines in Jinan is calculated. In addition,the calculation results are in good agreement with the borehole data,which can meet the accuracy requirements of engineering detection. This method provides a fast and accurate solution for determining the depth of the soil-rock interface in urban areas with strong disturbance.