综合物探方法在城市地质调查中的应用研究:以湖南省常德市鼎城区隐伏基岩探测为例

Study on application of comprehensive geophysical prospecting method in urban geological survey:taking hidden bedrock detection as an example in Dingcheng District,Changde City,Hunan Province

为在湖南省典型湖相盆地城市低阻覆盖区查明隐伏基岩及其空间分布状态,以常德市鼎城区G4线地质调查剖面为例进行了多方法综合试验研究。首先,介绍了研究区内地质、地层、构造等区域特征;其次,在使用高密度电阻率法和可控源音频大地电磁法进行野外探测试验基础上,引进了广域电磁法和微动勘探等新方法、新技术进行综合探测试验研究;最后,利用多方法探测结果推断了隐伏寒武系灰岩、断裂构造和地层垂向分布情况,并在靶区位置上进行了钻探验证,效果良好。本次调查研究表明:广域电磁法相比传统近地表探测方法,具有高抗噪、探测深度大等其他方法无法比拟的优点,是城市地质调查工作中探查基岩、隐伏构造等目标体的有效方法,而对于地表下百米以内的白垩系和第四系粉砂质地层划分,微动勘探具有明显的效果,值得推广。

In order to ascertain the hidden bedrock and its spatial distribution in the urban low-resistance coverage area of a typical Huxiang basin in Hunan Province,a multi-method comprehensive experimental study is performed using the G4 geological survey profile in Dingcheng District,Changde City as an example.Firstly,the geological,stratigraphic,and structural characteristics of the study area are introduced. Secondly, based on the use of high-density resistivity method and controllable source audio magnetotelluric method for field exploration experiments, new methods and technologies such as wide-area electromagnetic method and micro-motion survey are introduced for comprehensive exploration experimental research. Finally, multiple detection methods are used to infer the vertical distribution of hidden Cambrian limestone, fault structures, and strata, and drilling verification is carried out at the target area, with good results. This survey study indicates that compared with traditional near- surface detection methods, the wide-area electromagnetic method has advantages that are unmatched by other methods such as high noise immunity and large detection depth. The method has obvious effect on the detection of the Cretaceous and Quaternary silty strata within 100 meters, and it is worthy of promotion.