Simulation Study On Soil Hydrological Effect Of Opencast Coal Mine Dump In Micro Topography Shaping

Long-term mining in opencast coal mines will be piled up to form a dump.The soil structure of this artificial landform,which has been stripped and piled in large quantities,has undergone major changes.Under the action of repeated compaction by large machinery,the loose soil body undergoes non-uniform settlement,and the number of soil pores is drastically reduced.To a certain extent,it hinders the nutrient transportation of the soil to vegetation and microorganisms,resulting in varying degrees decline of soil water storage capacity and soil fertility,and soil erosion is serious.Affected by rain erosion for a long time,soil erosion is serious and secondary disasters occur frequently.Therefore,it is necessary to take effective measures to alleviate these situations.The reasonable layout of micro-topography can effectively adjust the distribution of water resources and play an important role in the control of soil erosion in the dumping site of the mining area.In this study,based on the data of the soil physical and chemical properties of the dumping site of Antaibao Opencast Mine in Shuozhou City,platforms(water retaining ridges,low-lying land)and slopes(horizontal trenches,horizontal steps,horizontal steps and horizontal trenches,with a spacing of 3 m or 5 m)micro-topography dumping sites were constructed in the Hydrus-3D numerical simulation software.The same rainfall and initial conditions were set for simulation,and natural,economic,and technical benefit indicators were selected to build a comprehensive micro-topography evaluation system.The main results are as follows:(1)Under the same rainfall condition,the change range of water content of dump platform is larger than that of slope.The influence of rainfall intensity on soil moisture content is different in different soil depth.The influence of surface soil is greater than that of deep soil.(2)In the same platform layout type,the order of cumulative infiltration of different micro-topography on the side slope is: horizontal trench 3 m> horizontal trench 5 m,horizontal step and horizontal trench 3 m> horizontal step 3 m,horizontal step and horizontal trench 5 m>horizontal step 5 m,while the cumulative runoff shows the opposite result.In the same slope micro topography layout plan,there is no significant difference in runoff and infiltration between the water retaining ridge and the low-lying land.(3)Among the 12 micro topography layout plans,the cumulative infiltration of retaining ridge and 3 m horizontal ditch increased by 32% and runoff decreased by 44.83% compared with the original dump.Considering the natural,economic and technical comprehensive benefits of the micro-topography consolidation measures,the water retaining ridge and horizontal trench3 m layout plan can be optimized for the control of soil erosion.The development of this research can provide a theoretical and scientific basis for the management of land reclamation and soil erosion in mining areas.