Soil Reclamation Models by Soil Water Infiltration for Refuse Dumps in Opencast Mining Area of Northern China

The water infiltration rules of five different homogeneously or heterogeneously-constructed soil samples were determined to select the best soil construction module for refuse dump reclamation in the opencast mines of the Shanxi-Shaanxi-Inner Mongolia energy circle. Five treatments, including three homogeneous soil samples consisting of sandy soil, Montmorillonite-enriched sandstone, and sand-Montmorillonite-enriched sandstone mixture, together with two heterogeneous soil samples composed of sandy soil + Montmorillonite-enriched sandstone + sandy soil and sandy soil + sandy − Montmorillonite-enriched sandstone mixture (7:3) + sandy soil. Three replicates of each treatment were prepared in the indoor pillars to measure the infiltration process by auto-recording geometry, to investigate the infiltration features of various soil configurations by testing their infiltration rate, cumulative infiltration capacity, wetting front migration, and profile soil content, and to evaluate the infiltration of newly constructed soil in the natural conditions of the research area. The experiment demonstrated that the addition of Montmorillonite-enriched sandstone into sandy soil significantly slowed down soil water infiltration, especially in the heterogeneous soils. Traditional models perfectly simulated the soil water infiltration in the three homogeneous soils in which soil infiltration capacity could be segmentally fitted by Kostiakov model and linear model, and wetting front could be fitted by a power function. Compared with the homogeneous soil samples, heterogeneous soil could reduce the direct surface runoff and deep percolation, and is an idealized structure for soil reconstruction in opencast coal mine dump