Experimental Study On Influencing Factors Of Soil Wind Erosion And Its Movement Characteristics In Northern Foot Of Yinshan Mountain

In recent years, the global climate is becoming warmer, the desertification of the soil in the northern Yinshan Mountain of Inner Mongolia is increasingly getting worse and sandstorm happens more frequently. To prevent the soil from further encroaching and ensure the stability of the economy in that region, the paper makes a study, based on the characteristics of soil desertification, to investigate the influencing factors of wind erosion of soil and its movement characteristics in the northern Yinshan Mountain of Inner Mongolia from the perspectives of moisture content, quality, gravity, mechanical stability and vegetation coverage of surface soil, and wind velocity, sand kinematics and hydrodynamics.The article deals with the following problems and fundamental results have been achieved.1. From the observation of the sandstorm, an analysis is made for the particles with the diameters of 0.05～1 mm with a unit of 0.025 mm collected by sand instrument. It is concluded that the wind erosion mass changes along with the height, that the mass percentage of different particle diameters changes along with the height, and that the percentage of different particle diameters changes regularly at the same height. It is shown how the soil particles of wind erosion are distributed in that region.2. Analysis of wind erosion matters shows, either in dry cultivated land or in common grass land, the diameter of wind erosion matters is graded into four degrees: the diameter less than 0.1 mm, most easily eroded; the diameter between 0.1～0.25 mm, more easily eroded; the diameter between 0.25～1 mm, easily eroded; and the diameter over 1 mm, not easily eroded.3. The surface of experimental area is covered by crust. It's observed, microscopically, that the crust in ordinary grassland is structured in sheet and in layer, like a compact plate; that the surface of the crust is smooth, however, the crust will become creviced but never friable when an external force is vertically acted on the crust by a man or animal. As to the cultivated land, the diameter of the crust particles increases, with fewer small particles, wider and more crevices. The crust is totally loosened and cracked by external forces.4. In light of dynamics theory and the forces acting on the single soil particle in air stream, the maximal saltation height(Hm) is calculated by four-fifth Runge-Kutta-Felhberg(RKF) method from the diameter of wind erosion matter(D) and its vertical initial speed (v0): H_m =( 3.7×10^-4 D^-1.1869) v₀^{0.2162lnD+1.7250}; at the specific swirl angular velocity (ω) and friction velocity(u^*), the maximal saltation length(Lm) is calculated: L_m = [a₁×10^-4D³+a2×10^-4D²-a3×10^-4D + a4×10^-4] v₀² +( b₁×D3- b₂×D² + b₃×D-b₄×10^-3) v0 -(c1×10³D³-c2×10³D² + c3×10³D-c4×10³). In contrast with the actual calculating results, the relevant coefficient is more than 0.99. These calculations are helpful to figure out the movement path of sands of different diameters.5. From theoretical calculation of the movement path of single soil particle, the particles with the diameter less than 0.075 mm are apt to drift. In the wind erosion matters collected by sand instrument, the percentage of those soil particles with the diameter less than 0.075 mm grows with the increasing height. It is indicated that the particles with the diameter less than 0.075 mm tend to flow away from the ground and drift high in the sky.