综合物探方法在古河道型地下水库工程建设中的应用研究

Application and research of integrated geophysical method in construction of paleochannel groundwater reservoir

以古河道为调蓄空间修建地下水库是有古河道分布的沿海地区防治海(咸)水入侵的重要措施之一.为了查明研究区古河道砂层分布特征,确定地下水库库址及库区信息,防止咸水入侵加剧,本文在分析研究区地层成因等地质条件的基础上,采用一维电测深法与高密度电阻率成像法相结合的地球物理方法对区内古河道进行勘探研究.结合钻探资料,从地层的电阻率这一综合物理参数角度分析研究勘探区域内的古河道特征.结果表明:电阻率参数能较好地反映研究区内的地层分布特征.古河道砂层整体上为高电阻率值反映,电阻率值在18~40Ω·m范围内,岩性以细砂、粉细砂为主;黏土层为低阻反映,电阻率值在5~18Ω·m范围内,构成古河道的顶底板及护坡结构.高阻体的空间结构特征较好地反映了古河道砂层的分布、埋深等信息,为古河道资源的合理开发利用奠定了基础,也为地下水库选址、确定边界条件、判别基底状况等提供了可靠的依据.

The underground reservoir by paleochannel as regulated capacity is one of the important measures to harness saltwater intrusion in coastal areas where paleochannel is distributed. In order to ascertain the distribution characteristics of sand in paleochannel,determine the location of underground reservoir and the related information about reservoir area and prevent the further deterioration of saltwater intrusion in the study area,on the basis of analyzing geological conditions of the area such as the origin of stratum,this study chose geophysical method which combined vertical electrical sounding and high-density electrical resistivity tomography is used to explore paleochannel. Compared with the drilling information,this study analyzed the paleochannel characteristics in the perspective of the stratum resistivity in exploration area. The results revealed resistivity parameter can better reflect the distribution characteristics of stratum in the research area. The sand in paleochannel is represented by the high-resistivity as a whole which is in the range of 18 ~ 40 Ω · m in the unconsolidated diagenetic zone whose lithology is mainly composed of fine sand and silty-fine sand and the clay in paleochannel is represented by the low-resistivity which is in the range of 5 ~ 18 Ω·m,constituting the top and the bottom floor and protection structure of paleochannel. The spatial structure of the high resistance can better reflected the distribution and the depth of sand in paleochannel. It will establish the foundation for rational exploitation and comprehensive utilization of paleochannel resource,can also provide reliable reference with selection of construction location, determination of boundary conditions and judgment of basement conditions of the underground reservoir in the future.