GPR-based depth estimation of ground interfaces in permafrost region: Electromagnetic method and cone penetration assessment

•An assessment method using electromagnetic waves and cone penetration is proposed.•The interface depths in active layer are estimated using the proposed method.•The ground conditions including cavity, groundwater level, and permafrost are predicted.•The prediction results are visually verified using an endoscope.•The proposed method can be a powerful tool for characterizing active layers. This study aims to estimate the interface depth in the active layer using nondestructive electromagnetic methods and cone penetration assessment. Ground penetrating radar (GPR) surveys, time domain reflectometry (TDR) measurements, and dynamic cone penetrometer (DCP) tests are conducted on the active layer. Ny-Ålesund in Svalbard is selected as the study area because of its distinct freeze–thaw cycles. The GPR survey detects the underground interfaces, and the relative permittivity of the ground is estimated using TDR measurement. Ground conditions are predicted using the depth-dependent relative density acquired from the DCP test. The results show that the interface depths estimated by GPR and TDR match well with the actual depths. The predictions of the cavity, groundwater level, and frozen layer using GPR polarity comparison are verified using an endoscope to match the actual ground conditions. This study demonstrates that GPR, TDR, and DCP tests may be robust tools for characterizing active layers.