| The use of heavy machinery during the process of dumping can result in the issue of severe soil compaction in opencast coal-mine area.Compaction affects soil coordination capacity for hydrological processes and increases the risk of soil erosion in mine areas.Simultaneously,rainfall intensity related to soil surface sealing is also one of the important factors affecting water transport.In this study,the effects of compaction and rainfall intensity on water transport from opencast coal-mine soil were analyzed by indoor soil column experiments.The soil used in the study was drawn from the Inner dumping site of Antaibao opencast mine,Shanxi Province,China.Four soil columns with different bulk density(1.4 g cm-3?1.5 g cm-3?1.6 g cm-3?1.7 g cm-3)were designed and each column was supplied water five times at rainfall intensities of 23.12 mm h-1?28.91 mm h-1?38.54 mm h-1?57.81 mm h-1?115.62 mm h-1,respectively,with a time interval of 10 days.HYDRUS-1D software was used to simulate the one-dimensional vertical unsaturated water transport.The results showed that,?1?During the saturation of the soil column,the order of capillary rate was:1.4 g cm-3>1.5 g cm-3>1.6 g cm-3>1.7 g cm-3.The order of time used for saturation was:1.7 g cm-3>1.6 g cm-3>1.5 g cm-3>1.4 g cm-3.The soil column with high bulk density exhibited the longest saturation time and the lowest capillary rise rate due to its lower capillary porosity.?2?Under the same compaction treatment,the order of change magnitude in the volumetric water content at all depths was:23.12 mm h-1>28.91mm h-1>38.54 mm h-1>57.81 mm h-1>115.62 mm h-1.The low rainfall intensity increased the volumetric water content of the soil bottom layer,while the high rainfall intensity only affected the volumetric water content of the surface layer,and it is difficult for water to infiltrate to the deep soil.High rainfall intensity reduced water infiltration,increased runoff and shortened the time to runoff.?3?Under the same rainfall intensity,the order of change magnitude in volumetric water content at all depths was as follows:1.4 g cm-3>1.5 g cm-3>1.6 g cm-3>1.7 g cm-3.The soil column of 1.6 g cm-3,1.7 g cm-3 bulk density exhibited low permeability.The soil with high bulk density reduced infiltration,increased runoff,and shortened the time to runoff.?4?The model efficiency coefficient?NSE?close to 1 and the root mean square error?RMSE?close to 0,which verified that HYDRUS-1D can be used to simulate the vertical unsaturated water transport under different rainfall intensities and bulk density.However,when the soil bulk density reached 1.6 g cm-3,the error measurement was recommended to use the NSE.?5?Engineering and vegetation measures are useful for improving the soil quality of opencast coal-mine dumps.This study can provide a theoretical basis for compacted soil reclamation and ecological reconstruction in opencast coal-mines. |
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