Analysis Of The Influence Of Meltwater Runoff During Spring Thaw On Sandy Slope Erosion Under Freeze-thaw Actio

The freeze-thaw erosion is widely distributed in the northeast area of China.Freezing-thawing erosion causes soil water to freeze,which makes the volume change,leads to soil expansion or contraction,and leads to soil structure destruction and property change,thus leading to soil erosion change and soil erosion increase.It has seriously affected the sustainable agricultural production,the protection of land resources and people’s production and life.At present,the lack of quantitative analysis on the erosion caused by melt water runoff in the spring thaw brings difficulties to the prediction and evaluation of soil erosion.In this paper,the change of physical and chemical properties of sand under freeze-thaw action was analyzed through the laboratory unidirectional closed freeze-thaw cycle test,and the influence of freeze-thaw action on soil erodibility was analyzed from the mechanism.Using the indoor meltwater erosion model,the erosion of soil caused by meltwater runoff in spring thawing period was studied by comparing the unfrozen slope with the freeze-thaw slope,and the erosion change of sandy soil slope in spring thawing period was studied.The following conclusions are drawn:(1)The freeze-thaw action can change the erodibility of sand by changing its physical and chemical properties such as bulk density,porosity and permeability.The freeze-thaw action can reduce the bulk density of soil and increase the porosity.The permeability of sand increases with the increase of the number of freeze-thaw cycles,and the changing trend is highly similar to that of porosity.The increase of freezing-thawing temperature difference and initial water content of soil samples will lead to the decrease of bulk density and the increase of porosity and permeability.(2)In the process of slope erosion,the erosion amount of freezing-thawing slope is larger than that of unfrozen slope.The runoff sediment content of unfreezing-thawing slope increases first and then tends to be stable,while the runoff sediment content of freezing-thawing slope increases first and then decreases,and then tends to be stable.Soil erosion resistance is greatly affected by temperature and time,and different slope lengths have significant differences on soil erosion resistance.Under the same slope height,the thicker soil layer is,the better its erosion resistance is.The erosion modulus of both unfrozen and frozen slopes increases with the duration of erosion.Under the same slope condition,the growth rate of erosion modulus k increases with the increase of initial discharge.The anti-scourability coefficient of soil samples decreased with the increase of slope.(3)The existence of temperature difference provides the necessary conditions for freeze-thaw erosion,and the slope erosion increases with temperature difference.Similar to the influence of temperature difference on slope erosion,slope erosion increases with the increase of water content,and the increase has a tendency to expand with the increase of the number of freeze-thaw cycles.