Study on Application of Comprehensive Geophysical Prospecting Method in Urban Geological Survey—Taking Concealed Bedrock Detection as an Example in Dingcheng District, Changde City, Hunan Province, China

Abstract

In order to ascertain the concealed bedrock and its spatial distribution in an urban low-resistance coverage area of a typical lacustrine basin in Hunan Province, a multi-method comprehensive experimental study was carried out in Dingcheng District, Changde City where there are multiple sets of strata and fault structures. In this study, the wide-area electromagnetic method and microtremor survey were utilized on the basis of traditional methods, including the high-density resistivity method and controlled-source audio-frequency magnetotelluric method, to infer the concealed Cambrian limestone, fault structure, and vertical distribution of strata and the results were verified by drilling. The results indicate that the wide-area electromagnetic method is effective to explore the bedrock and concealed structure in urban geological survey. The microtremor method has an obvious effect on the detection of the Cretaceous and Quaternary silty strata within 100 m. The study may provide references for similar projects in this area.

Detection of Landfill Leachate Leakage Based on ERT and OCTEM

“…Electrical methods lay detection electrodes or conductive gridlike fibers under the impermeable layer, and determine the leakage location according to the electromotive force distortion or short circuit of conductive fibers. However, they have a low safety factor, and conductive fibers are prone to misalignment [32][33][34][35][36]. Acoustic methods lay multiple vibration sensors under the impermeable layer that are used to locate and receive the instantaneous damage signals of the HDPE film.…”

“…The disadvantage of the dipole method in the direct electric current method detection system is that the current significantly attenuates with an increase in measurement distance, that is, the covering the thickness and conductivity of the waste layer affects the potential distribution. The thicker the garbage layer is, the weaker the surface potential distribution, and the lower the detection sensitivity are, and, thereby, the greater the error is in determining the location and number of holes [32][33][34][35][36]. The potential distribution of the current field in the electrode grid method is directly related to the layout of the detection electrodes under the film [44].…”