Transient electromagnetic S-inversion in tunnel prediction

This paper presents S-inversion method to tunnel prediction to forecasting water-filled faults or fracture zones ahead of the front wall of a tunnel during tunnel excavation. S-inversion is an interpretation method of transient electromagnetic (TEM) data using the second derivative of the conductivity parameter based on the moving thin sheet approach. It is suggested for the technology of second derivative of vertical apparent conductivity, which is traditionally used in surface TEM data interpretation, the theoretical analyses and the method of numerical calculation in detail are also given. Finally, a real tunnel forecasting is studied for TEM surveys, and results show that the proposed method is effective and successful for exploring and predicting unfavorable geology during tunnel construction. Citation: Xue, G. Q., Y. J. Yan, X. Li, and Q. Y. Di ( 2007), Transient electromagnetic S-inversion in tunnel prediction, Geophys. Res. Lett., 34, L18403, doi: 10.1029/2007GL031080.