The dumping site is the most serious soil erosion area in an industrial and mining construction area. The development of cracks and water movement in the dumping site is the main factors that induce slope collapse. In this text, the influence of the crack width, rainfall intensity, and two simulation methods of hydrological processes are investigated under artificial rainfall conditions. The results show that the total runoff is affected by two factors, namely rainfall intensity and crack width, and the total runoff decreases with the increase in the crack width. The stable infiltration rate decreases with the increase in the crack width under the same rainfall intensities. When the rainfall intensity is greater than 90 mm/h, the contribution of leakage to the total infiltration is more than 50%. Under simulated rainfall conditions, the total runoff of the solid model was reduced by 5% to 13% compared with the equivalent model. Hence, the cumulative leakage of the solid model is 29% to 71% larger than that of the equivalent model under the same conditions. In this text, the transformation equations from the solid model of the dump site to the equivalent models of runoff, infiltration, and leakage are constructed, and then it can be corrected by the fitting equation.

There are a large number of macropores/tubular channels of a few centimeters and plant roots in reclaimed dump soils, which are the main reasons for the formation of soil macropores and soil preferential flow. To systematically study the morphological characteristics and variation of soil preferential flow for different reclaimed vegetations in a dump, a dye-staining experiment and physical and chemical analysis were carried out to investigate the formation mechanism and influencing factors of soil preferential flow in the vegetation restoration process. The results indicate that there were differences in the soil water breakthrough curves for different plots. The macropore effluent rate generally increased at first and then tended to stabilize. The soil steady effluent rate decreased with increasing soil depth, which reached the maximum and minimum values at the depths of 0∼5 cm (0.0193∼0.0315 mm s) and 50∼60 cm (0.0028∼0.0035 mm s), respectively. Furthermore, the radius of soil macropores under different types of reclaimed vegetation ranged from 0.03 to 4.71 mm, most of which ranged from 0.11 to 2.36 mm. The soil macroporosity of different reclaimed vegetation types ranged from 0.03 to 16.58%, which was significantly greater than 5%. The soil macroporosity determined 65% of the variation in the steady effluent rate and 42% of the variation in the saturated hydraulic conductivity. Furthermore, the dye coverage ratio decreased as the soil layer depth increased in different plots, and there were some differences in each plot. The maximum dye coverage ratio occurred in the 0∼5 cm soil layer, which reached 90.37%. The dye coverage ratio at a depth of 0∼60 cm in six plots followed the order of Robinia pseudoacacia (26.48%) > Ulmus pumila (20.12%) > mixed forest (17.32%) > farmland (15.06%) > shrub (13.97%) > weeds (10.07%). The soil preferential flow mostly occurred in the 0∼40 cm soil depth layer, which occupied more than 93% of the total soil profile (0∼60 cm). Moreover, a Pearson correlation was used to analyze the relationship between environmental factors (soil, water, and plant factors) and the dye coverage ratio. The dye coverage ratio of soil preferential flow under different reclamation vegetations was very significantly or significantly positively correlated with the gravel content, mean radius of soil macropores, soil saturated hydraulic conductivity, root weight density, and root length density, which promoted the formation and development of soil preferential flow. This study will provide a scientific basis for understanding the formation mechanism and perfecting the research system of soil preferential flow, vegetation restoration, and reconstruction in a dump; furthermore, this research offers significance guidance in the construction of green mines and the development of regional economics.

The dump, with the compact rock platform and high and steep loose slope that is formed during coal mining, is the most serious area of soil erosion in a surface coal mine. Ground fissures are a typical geological hazard in coal mining areas. However, the effect of ground fissures on soil erosion remains unclear. Rainfall experiments were conducted to determine the varying characteristics of wetting front, runoff and sediment production, and soil denudation rate, as well as the effects of ground fissures on these factors in a platform-slope system of a dump. Ground fissures could significantly enhance wetting front and soil erosion. Rill erosion was formed as the rainfall and runoff flushed the soil, which eventually developed into erosion gullies. Erosion failure modes with platform-slope systems in the dump could be divided into the surface erosion stage, fissure deformation stage, rill erosion stage, fissure collapse-rapid increase stage, and stable stage. Runoff power and flow shear stress had the greater influence on soil denudation rate, which indicated that erosion energy of concentrated flow had important influence on soil erosion. Moreover, shallow mudflow induced by rainfall was one of the forms of soil slope instability; it occurred in a short time with great soil erosion. Soil erosion in the dump with ground fissures was mainly shallow mudflow and rill erosion, resulting from the combined effect of hydraulic erosion and gravity erosion.

Ground fissures (GF), appearing in front of dumps, are one of the most obvious and harmful geological hazards in coal mining areas. Studying preferential flow and its influencing factors in the ground fissures of dumps may provide basic scientific support for understanding the rapid movement of water and vegetation restoration and reconstruction in mining areas. Based on field surveys of ground fissures, three typical ground fissures were selected in the studied dump. The morphological characteristics of preferential flow for ground fissures were determined through field dye tracing, laboratory experiments, and image processing technology. The results indicated that the lengths of the three ground fissures ranged from 104.84 cm to 120.83 cm, and the widths ranged from 2.86 cm to 9.85 cm. All of the ground fissure area densities were less than 10%, and the proportion of ground fissure surface area was small in the dump. The maximum fissure depth was 47 cm, and the minimum was 16 cm. The ground fissure widths ranged from 0 cm to 14.98 cm, and the fissure width and fissure width-to-depth ratios decreased with increasing soil depth. The stained area was greater than 90% in the 0–5 cm soil layers of the three fissures, and water movement was dominated by matrix flow. The stained width decreased from 90 cm to 20 cm with increasing soil depth. The preferential flow was mainly concentrated on both sides of the fissure, which was distributed as a “T” shape. The preferential flow stained area ratios were 27.23%, 31.97%, and 30.73%, respectively, and these values decreased with increasing soil depth. The maximum stained depths of the preferential flow among the three fissures were different, and the maximum stained depth of GF II was significantly larger than that of GF I and GF III (P < 0.05). The stained path numbers of the three fissures ranged from 0 to 49. With increasing soil depth, the stained path number first increased and then decreased. The stained path widths of the three fissures ranged from 0 cm to 90 cm. With the increase in soil depth, the stained path width decreased. The stained area ratio was significantly positively correlated with ground fissure width, the ground fissure width-to-depth ratio, soil saturated hydraulic conductivity, soil organic matter, and sand content and was significantly negatively correlated with soil water content and clay content. The stained path number was significantly positively correlated with ground fissure width, the ground fissure width-to-depth ratio, soil saturated hydraulic conductivity and soil organic matter. The stained path width was significantly positively correlated with the ground fissure width-to-depth ratio, soil saturated hydraulic conductivity, soil organic matter and sand content and was significantly negatively correlated with clay content. Plant roots could significantly increase the stained area ratio, stained path number, and width and promote the formation and development of preferential flow.