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Abstract Analytical solutions in homogeneous half-space are joined as initial conditions in almost all the forward of transient electromagnetic method(TEM)，no problem when the model has an analytical solution. However，it is not suitable for TEM advanced geological prediction in tunnels with a homogeneous whole space because of the excavation. According to Maxwell equations and on the basis of 3D transient eddy current field equations and circuit equation，we establish a field-circuit coupling model based on vector magnetic potential formulation. Node method is used during the time discretization；and a Galerkin form time discrete equation is established. The model achieves the goal of using voltage as excitation source in 3D forward of TEM，which makes the 3D forward much nearer to the actual situation. The famous smoking effect in TEM is simulated based on the field-circuit coupling method. Comparison between the simulation results and the analytical values show that the numerical simulation is consistent with the practice. Two models with and without consideration of effects of seawater are established and analyzed according to Qingdao subsea tunnel. The field-circuit coupling method is used and the effects of the seawater above the tunnel are collected.
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Received: 14 February 2011
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2011, Vol. 30 
