Three-dimensional Forward Modeling Of Urban Comprehensive Shallow Electric Ground Exploration

Due to the rapid development of urbanization in China,the situation of urban groundwater pollution is increasing,and the prediction of shallow groundwater in cities has become an urgent problem for major cities.Geophysical electrical exploration is extremely sensitive to geological body resistivity differences and has significant advantages for groundwater detection.By providing a stable DC electric field or a transient electromagnetic field,electrical exploration can detect the extent of the groundwater low-resistance anomaly zone and speculate on the occurrence characteristics of the groundwater body.This paper proposes to use the long electrode resistivity method to survey groundwater.Since the long power supply electrode can be buried deep underground and provide more current into the deep stratum,its geoelectric field reflects more deep information.Transient electromagnetic method is a mature geophysical survey method.Pulse current is used to excite transient electromagnetic field through grounding wire or ungrounded return line.In the process of electromagnetic field propagation,an induced current is formed in a low-resistance anomaly.In the secondary field,by accepting the secondary field,the transient electromagnetic method can obtain the geological information of the underground space.In this paper,the transient electromagnetic method and resistivity method are used to simulate the shallow groundwater in the city.The finite element numerical simulation software COMSOL is used to simulate the electromagnetic field anomaly characteristics of shallow groundwater in urban areas.