Study on forward modeling of tunnel IP 3D advanced detection technology

Aiming at the key technology of tunnel advance detection, fast forward modeling on 3D complex conditions of tunnels was realized by 3D finite element numerical simulation t echnique .Based on 3D fast forward modeling and program, this paper analysed and calculated the influence laws of tunnel itself and lateral abnormal bodies on induced polarization ( IP) dete ction of tunnel floor.The least squares ftting formula was aplied to deduce the approximate correcting formula which could correct the the inference of super high resistivity of the tunnel itsel f.Results of research showed that the approximate correcting formula had a good ftting effect on the influences of tunnel itself, the ftting error was less than 3%, and could be used for actual t unnel influence correction.For tunnel front advanced detection, compared to the abnormal of resistivity, apparent polarization abnormal gained by three electrode method has better effects of a . dvanced detection, for advanced detection of tunnel floor and side wall, three electrode method is usually applied to reflect geo-electric information on the outer direction of the line surface.