Influence of Different Mining Damage Types on Soil Erodibility in Coal Mining Areas of Northern Shaanxi in the Middle Reaches of the Yellow River in China

Abstract

The middle reaches of the Yellow River basin are not only rich in coal resources in China, but are also a typical experimental field for studying the law and mechanism of soil erosion caused by coal mining in the area. Grasping the differences in soil’s physical and chemical properties caused by different types of mining damage and then analyzing the differences in soil erosion is conducive to achieving ecological environmental protection and high-quality development in coal mining areas, thus improving soil and water conservation efficiency and saving costs. In this study, we took the typical loess subsidence slope of Ningtiaota mine field in the northern Shaanxi coal mining area as the research object, collected the soil samples at different slope positions, and measured the soil mechanical composition and organic matter mass fraction using an MS2000 laser particle size analyzer and a total organic carbon analyzer, respectively. Based on the EPIC model, the soil erodibility K value was further calculated, the spatial variation characteristics of the soil’s mechanical composition and organic matter mass fraction were analyzed, and the soil erosion effect under different mining damage types was interpreted. The results are as follows: ① The subsidence of loess slope and the development of mining ground fissures will reduce the clay mass fraction and increase the sand mass fraction in the shallow soil on the slope. The clay mass fraction of the whole slope will decrease by 4.50–30.30%, and the soil sand mass fraction will increase by 6.83–23.67%. The shallow soil at the top and middle of the slope has obvious sandy characteristics, and the amount of sandy soil in the crack area of the same slope is obviously higher than that in the non-crack area. Slope position is the main reason to control the shallow soil sand on the slope of loess subsidence in the northern Shaanxi coal mining area. ② The subsidence of loess slope and the development of mining ground fissures will lead to a decrease in organic matter mass fraction in shallow soil in different amounts. The decrease in organic matter mass fraction in the whole slope is 12.68–35.46%, and the decrease in organic matter mass fraction in shallow soil at the top and middle of the slope is significant, and the loss of organic matter in the crack area of the same slope is obviously higher than that in the non-crack area. The greater the width of the mining ground fissures and the smaller the horizontal distance from ground fissures, the more organic matter mass fraction in shallow soil will decrease. Mining ground fissures are the main factors when it comes to controlling the loss of organic matter in the shallow soil on the loess subsidence slope in northern Shaanxi coal mining area. ③ The negative correlation coefficients of shallow soil erodibility K value with the soil clay mass fraction and organic matter mass fraction all exceeded 0.6, a significant level, and there is a high degree of consistency in the change characteristics of the slope scale. The subsidence of the loess slope and the development of the mining ground fissures will have the effect of improving the erodibility of shallow soil in all parts of the slope. The erodibility of shallow soil at the top and middle of the slope increases significantly, and the erodibility of shallow soil in the crack area of the same slope is obviously higher than that in the non-crack area. The larger the width of the mining ground fissures and the smaller the horizontal distance from the ground fissures, the higher the erodibility of the surrounding shallow soil. After calculation, it was found that the maximum boundary of the mining ground fissures developed on the loess subsidence slope in northern Shaanxi coal mining area to improve the erodibility of the surrounding shallow soil was 115 cm, and the main action range was concentrated within 90 cm. These research results can provide a scientific basis for accurate prevention and control of the soil erosion effect of mining subsidence in loess coal mining in the area of northern Shaanxi, thus saving costs.