Optimum Combination Test of Erosion Gully in Black Soil Regions by Coal Gangue Reconstruction Soil

The black soil area in northeast China is greatly affected by hydraulic erosion. To inhibit the development of gully cutting and the secondary erosion on farmland, different size coal gangues and covering soils with change thicknesses combinations were selected to fill in-situ gully for hydraulic performance experiment. The hydraulic performance indexes of different combinations of large and small size gangue thicknesses and covering soil thicknesses were analyzed by the extreme learning machine（ELM） and particle swarm optimization（PSO）. The results showed that the structure of large and small size coal gangues and surface soil under different thicknesses was affected by hydraulic and gravity. With the change of the thicknesses of coal gangue and covering soil, its effective channel and vertical infiltration process became more and more stable with the increase in drainage time, while the structure of small size coal gangue was the main hydraulic factor in reconstructed soil structure（p=0.016）. The overall drainage performance showed a single peak trend, the optimal combination of drainage parameters and structure thickness was relatively concentrated; the drainage time parameters of different composite structures were found to have a certain linear relationship; the Pareto optimum of drainage performance was determined. The optimum thickness was 30-40 cm for large-sized gangue, 30-60 cm for small-sized gangue, and 50-70 cm for covering soil, to meet the relatively good drainage performance and to ensure that secondary erosion was reduced, so as to achieve the purpose of controlling the gully.