Prediction of the soil water characteristic curve in an opencast coal mining area based on CT scanning technology

With the rapid increase of mechanization, the compaction caused by repeated mechanical operations and waste accumulation in open-pit coal mine areas will cause the destruction of land resources, resulting in soil degradation and ecological imbalance. Clarifying the impact of compaction on soil hydraulic characteristics is of great practical significance for land reclamation, and water and fertilizer management. In this study, the surface soil was collected from the dump of Antaibao opencast coal mine in Pingshuo mining area, Shanxi Province, and two groups of experimental soil samples were prepared in the laboratory. The bulk density range was 1.3-1.8 g/cm³,and the bulk density interval was 0.1 g/cm³. One group of samples was used to determine the water characteristic curve by centrifugation in the laboratory, and the other group was based on the CT scanning technology combined with three-dimensional reconstruction technology of soil macropores to predict the water characteristic curve within the compaction range. By comparing the difference between the predicted value and the measured value based on statistical method, the prediction performance of the physical empirical model was verified, and the influence mechanism of compaction on soil water characteristic curve was analyzed. The results showed that the CT scanning technology can quickly and easily obtain the distribution characteristics of soil macropores, and with the increase of compaction degree, the number of soil macropores and macro-porosity significantly decreases, effectively reducing the connectivity between soil pores. For the predicted value of the soil moisture characteristic curve, it is found that in the predictable range of bulk density, the soil water content decreases rapidly with the increase of compaction, which is mainly due to the compaction's alteration on the distribution characteristics of soil macropores, the internal compaction of the soil, and the reduction effect of water storage. The predicted value and the measured value vary with the bulk density in the same way, and the prediction accuracy of the model is higher.