Effects of mining ground fissures of different shapes on soil erodibility in Northern Shaanxi coal mining area

The middle reaches of the Yellow River Basin, as a national key prevention and control area of soil and water loss, is of great significance to solve the contradiction between coal mining and soil and water conservation for the protection of ecological environment and high-quality development of mining areas. The mechanical composition and organic matter content of soil were measured, and the soil erodibility K value was calculated based on EPIC model. The spatial variation characteristics of soil mechanical composition and organic matter content under the influence of different forms of mining ground fissures were analyzed, and the soil and water loss effect of different forms of mining ground fissures on a small spatial scale was interpreted. The results showed that:① the mining ground fissures in three forms of "horizontal opening", "step type" and "combined type" led to the obvious decrease of soil clay content and organic matter content and the obvious increase of soil erodibility K value. The average decrease of soil clay content was 21.50%, 43.93% and 58.70% (p<0.05), respectively, and the average decrease of soil organic matter content was 45.72%, 61.79% and 78.66% (p<0.05), respectively. The average increase of soil erodibility K value was 12.49%, 17.82% and 32.35% (p< 0.05), respectively and the horizontal negative effect was the main effect. ② At the same horizontal distance and vertical depth, the ability of "combined" cracks to reduce soil clay content, organic matter content and increase soil erodibility K value was significantly higher than that of "open" and "stepped" cracks, and the order was "combined type" > "stepped type" > "flat type". ③ Based on the exponential function, the action range prediction models of three forms of mining ground fissures affecting the K value of surrounding soil erodibility were established respectively. It was found that the action range of different forms of ground fissures to improve the erodibility of surrounding soil was basically within 155 cm. Combined with the comparative analysis of the significance of the difference, the "flat opening", "step type" and the key action range of "combined" mining ground fissures to improve the erodibility of surrounding soil was within 40, 60 and 100 cm, which can be used as an accurate prevention and control target for the effect of water and soil loss under the small spatial scale of mining ground fissures in Northern Shaanxi mining area. The results can guide the precise prevention and control of soil and water loss in the coal mining area of Northern Shaanxi and even the middle reaches of the Yellow River Basin.