Soil erosion effect of subsidence deformation superimposed freeze-thaw action on loess slope in coal mining area of northern Shaanxi in the middle reaches of the Yellow River

Deeply understanding and scientifically resolving the contradiction between coal mining and soil erosion is an important cornerstone for achieving ecological protection and high-quality development in the middle reaches of the Yellow River. Taking the loess mining subsidence area in northern Shaanxi as the research area, from the perspective of “coal mining subsidence + freeze-thaw action” coupling, taking mining thickness, natural morphology of surface loess slope and freeze-thaw action as research variables, through numerical simulation test, freeze-thaw cycle test, soil loss model calculation and other methods, the influence of freeze-thaw action on soil mechanical composition, organic matter mass fraction and soil erodibility K value is revealed, and the soil erosion effect of slope subsidence deformation superimposed freeze-thaw action is clarified.The results showed that: Under the condition of any initial soil moisture content and freeze-thaw times, the texture type of slope soil would not change, but the mass fraction of soil clay, sand and organic matter was negatively correlated with the initial soil moisture content and freeze-thaw times, with the decrease of 3.72%−31.69%, 1.05%−16.52% and 4.62%−13.06%, respectively. The erodibility K value of the slope soil was positively correlated with the initial water content and the number of freeze-thaw cycles, and the increase was between 1.19% and 8.03%. Under the condition of the initial water content of the soil, the increase of the erodibility K value of the slope soil reached the maximum and remained stable after 9 freeze-thaw cycles. For every 1% increase in soil initial water content, the increase of erodibility K value increased by 2.917%−12.187%. Compared with the natural slope, under the same initial water content and freeze-thaw cycles, the effect of “subsidence + freeze-thaw” has the effect of increasing the soil erosion modulus, and the increase of soil erosion modulus(M₁^*) is between 4.17% and 31.93%. The greater the mining thickness, the greater the increase of soil erosion modulus(M₁^*); under any mining thickness and slope shape, when the natural slope is 5°−15°, the increase of soil erosion modulus(M₁^*) is obvious. When the mining thickness is 7−9 m + concave slope of any natural slope, the increase of soil erosion modulus(M₁^*) is the most significant. The increase of soil erosion modulus(M₁^*) was positively correlated with the initial soil moisture content and the number of freeze-thaw cycles. Among them, the increase of soil erosion modulus(M₁^*) reached the maximum and remained stable after 9 freeze-thaw cycles. Under the given number of freeze-thaw cycles, the increase of soil erosion modulus(M₁^*) increased by 3.00%−62.50% for every 1% increase of initial soil moisture content. The ' subsidence + freeze-thaw ' will amplify the soil erosion modulus(M₁^*) increase of the surface subsidence slope, and the increase magnification is between 1.06 and 3.79 times. The magnification of the soil erosion modulus(M₁^*) increase is negatively correlated with the mining thickness. When the mining thickness is 5−9 m + natural slope is 45°, the amplification effect of soil erosion modulus(M₁^*) is the most obvious. The magnification of soil erosion modulus(M₁^*) increase was positively correlated with the initial moisture content and the number of freeze-thaw cycles. Among them, the magnification of soil erosion modulus(M₁^*) increase reached the maximum and remained stable after 9 freeze-thaw cycles. Under the given number of freeze-thaw cycles, for every 1% increase in the initial soil moisture content, the magnification of soil erosion modulus(M₁^*) increases by 0.25% to 3.21%. It can provide scientific basis for the precise prevention and control of soil erosion in the coal mining subsidence area of northern Shaanxi in the middle reaches of the Yellow River.