Variability in reconstructed soil bulk density of a high moisture content soil: a study on feature identification and ground penetrating radar detection

The complex formation process of reconstructed soil triggers the high spatial variability of soil physical properties, for which traditional soil sampling methods are not applicable due to the destructive and time-consuming modes. Ground penetrating radar (GPR) can collect continuous and high-resolution data flexibly, but the technology has rarely been employed to detect reconstructed soil properties in opencast coalmine regions. This study explored the applicability and accuracy of GPR in measuring reconstructed soil bulk density (RSBD) in southern dump, expanded western dump, and internal dump of the Antaibao open-pit mine, China. The variations of RSBD and the relationships between the dielectric constant and RSBD were analyzed based on ring knife sampling weighing, GPR detection, variance analysis, and fitting analysis. The results showed that (1) RSBD exhibited significant variations in different dumps and at different depths of the same profile. (2) RSBD differences in different dumps could be qualitatively analyzed based on the large-amplitude signals in GPR images. (3) When the soil volume moisture content ranged from 15 to 25%, RSBD was found to be negatively correlated with the dielectric constant. GPR has the potential to be widely employed to detect RSBD in reclaimed lands, which can contribute to the development of non-destructive quality testing of land reclamation.