Abstract:

The integrated engineering geological investigation in shallow waters has disadvantages such as low exploration precision and resolution. Therefore, the transient electromagnetic method is introduced into the engineering geological investigation in shallow waters. The research results of existing achievements of the transient electromagnetic method are analyzed. Based on the Maxwell equations, a highprecision transient electromagnetic field response formula based on multiturn rectangular and small frame current source in shallow water is derived, and the induced voltage expression is obtained. The simulation model of shallow water layer and water bottom half space is designed to calculate the transient electromagnetic response of shallow water layer. The optimal inversion technique of highprecision transient electromagnetic in shallow waters is studied, and the feasibility and effectiveness of the forward inversion method are verified by practical projects. Through the comparison and analysis of simulation model calculation and measured data, it is proved that the forward and inversion method is fast and accurate, which can effectively solve the geological problems such as soil and water boundary, soil and rock boundary, karst and fracture in engineering investigation.

Key words: transient electromagnetic method, shallow water area, integrated engineering geological survey, forward modeling, inversion calculation