Non-destructive detection of soil volumetric water content in reclaimed soils in an opencast coal mine using hyperbolic reflection in GPR images

The mining and reclamation of opencast coal mines affect the soil volumetric water content (SVWC¹). An accurate measurement of the SVWC is critical for land reclamation. However, traditional methods often damage the soil structure and are time-consuming. Thus, a rapid and non-destructive method is required to measure the SVWC in reclaimed mining areas. This study aimed to evaluate the feasibility and effectiveness of using ground penetrating radar (GPR) for estimating SVWC in reclaimed mining areas. We obtained GPR data and collected soil profile samples from the South Dump of the Antaibao opencast coal mine in Pinglu District, Shuozhou City, Shanxi Province. Random Hough transformation and inverse distance weighted interpolation were used to analyze the two-dimensional soil water layer thickness (SWLT) and SVWC in different soil layers and profiles. The radar estimated and the sampling measured value of SVWC were consistent with the soil depth. The Pearson correlation coefficient (r) between the radar estimated and the sampling measured values of SVWC was 0.850 in different soil layers, the lowest root mean squared error (RMSE) was 0.43%, and the lowest relative root mean square error (RRMSE) was 3.80%. The r was up to 0.959, the lowest RMSE was 0.58% to 0.90%, and the lowest RRMSE was 1.46% in different profiles. These results demonstrate the method’s feasibility and effectiveness, enabling the precise non-destructive estimation of SVWC. The results provide valuable technical support for the efficient reclamation and restoration of mining areas.