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How to solve the contradiction between coal mining and soil and water conservation is the key scientific problem to realize the ecological environment protection and high-quality development in the middle reaches of the Yellow River. In this paper, taking the coal mining subsidence area in loess gully of northern Shaanxi as the research object, aiming at the typical geological occurrence characteristics of the main coal seam, and taking the underground mining thickness (9, 7, 5 m), the natural slope shape (straight slope, concave slope, convex slope, compound slope) and slope (5°, 15°, 25°, 35°, 45°) of the surface loess as variables, a total of 60 numerical models are constructed. In this paper, based on FLAC3D numerical simulation software, the evolution process and law of slope morphology under the coupling effect of loess natural slope morphology and mining thickness are studied. Then, based on China soil erosion equation (CSLE model) and empirical model, the soil erosion effect of subsidence slope is calculated and analyzed. The results show that: ① Coal mining subsidence will lead to the increase of the slope of the surface loess slope, and the greater the mining thickness, the greater the slope increase. Significant Amplification Effect of Large Mining Thickness on Slope Gradient Increase of Surface Loess Caused by Coal Mining Subsidence. The concave slope generally has a significant effect on the slope of the subsidence slope, especially under the conditions of “ mining thickness 5 m, natural slope > 5 ° ”, “mining thickness 7 m, arbitrary natural slope ”, “ mining thickness 9 m, natural slope ≤ 35°”. No matter what kind of mining thickness and natural slope shape, the natural slope of ≤ 5 ° has the greatest influence on the increase of subsidence slope. ② Coal mining subsidence will lead to the increase of M1 on the surface loess slope under the scale of “ annual erosion rainfall ”, and the greater the mining thickness, the greater the increase of M1. When the mining thickness increases from 5 m to 9 m, M1 increases by about 1 time. The concave slope of four slope shapes has the greatest influence on the increase of M1 on the subsidence slope. The natural slope of ≤ 15° has a great influence on the increase of M1, which is more than 20% under the condition of “ mining thickness 9 m, concave slope ”. ③ Coal mining subsidence will lead to the increase of M2 of surface loess slope under the scale of “ typical erosion rainfall ”, and the greater the mining thickness, the greater the increase of M2 ; when the mining thickness increases from 5 m to 9 m, the increase of M2 increases by about 1 times. The concave slope of the four slope shapes has the greatest influence on the increase of M2 on the subsidence slope. The natural slope of ≤ 15° has a great influence on the increase of M2, which is more than 17 % under the condition of “ mining thickness 9 m, concave slope ”. The results can provide scientific basis for accurate prevention and control of soil erosion and high-quality development in the mining area of northern Shaanxi and even the middle reaches of the Yellow River Basin.

The destruction of shallow aquifers by water-conducting fractures of overlying strata caused by underground coal mining is the most representative form of mining-induced damage in the Yushenfu mining area. It has become an important factor restricting the green mining of coal in the Yushenfu mining area and even the ecological protection and high-quality development of the middle reaches of the Yellow River. As the key scientific problem of water-preserved coal mining, the scientific understanding of the development law and main influencing factors of water-conducting fractures in overlying strata has attracted great attention. Taking the geological occurrence characteristics of the main coal seam in Yushenfu mining area as the prototype, 24 different types of numerical models are constructed with the key characteristics of the overburden structure, such as the number of layers of sandstone in the overburden (sand layer coefficient) and the thickness ratio of sandstone and mudstone in the overburden (sand–mud ratio), as the main variables. By means of numerical simulation experiment and theoretical calculation, combined with field measurement and comparison, the influence of the key characteristics of overburden structure on the development height of water-conducting fracture is studied and revealed. It is proposed that the effective area for the study area to achieve water-preserved coal mining by using the height-limited mining method must conform to the coal seam overburden structure characteristics of "sand–mud ratio 6:4 and sand layer coefficient less than 70%" and "sand–mud ratio 8:2 and sand layer coefficient less than 80%". The results not only enrich and deepen the research on the influence of geological factors and the law of controlling the development of water-flowing fractures in overlying strata, but also provide theoretical support for the precise protection of groundwater resources in the Yushenfu mining area in the middle reaches of the Yellow River. [ABSTRACT FROM AUTHOR]