A time-domain feature-based discrimination method for leakage-channel structural locations under leakage-current coupled excitation

To discriminate the structural locations of leakage channels in the seepage-control system of earth-rockfill dams, this study proposed a non-destructive testing scheme based on transient electromagnetic responses under leakage-current coupled excitation. A realistic dam model, including the core wall, cut-off wall, deep overburden layers and conductive leakage channels, was developed to analyse the spatiotemporal characteristics of the magnetic flux density time derivative (dB/dt). The results indicated that all three dB/dt components in the early transient stage reflected the horizontal features of leakage channels. Zero-crossing features dominated the x- and z-components, whereas the y-component was controlled mainly by peak-amplitude features and yielded more stable discrimination. Along the depth direction, the peak time of the y-component was delayed as the burial depth increased and remained indicative within the cut-off-wall-related depth range. When the half-decay time parameter was introduced, the leakage channels in different structural zones exhibited distinct linear time–depth relationships during the decay stage. By integrating early-stage spatial features with time-domain characteristics, a time-domain-feature-based scheme was established for the rapid non-destructive discrimination and quantitative evaluation of leakage structural locations in earth-rockfill dams.