| The fragile ecological environment of arid desert open-pit mining area is an important problem to be solved in production and development.The arid area of Northwest China is one of the main areas with active sandstorm.In addition to the influence of coal mining industry and human disturbance,the destruction of vegetation and material structure accelerates the sandstorm activity,resulting in the further deterioration of fragile ecological environment,Therefore,the dust prevention and control in the mining area is an urgent problem in the ecological restoration.In order to study the law of aeolian sand in the mining area,the sand source area of the underlying surface of the openpit mining area in Wuhai City is selected as the research object,The types of underlying surface in the mining area are divided,The wind speed,wind speed profile,the law of wind sand flow differentiation,the characteristics of dust particle size and the monthly variation of dust horizontal flux were studied.The findings are as follows:(1)The underlying surface of the mining area is divided into 3 types and 10 types.The three type groups are Type group of underlying surface of gravelly soil,type group of sand underlying surface,type group of clay underlying surface.The 10 types of underlying surfaces are block dry underlay,boulder dry underlay,breccia dry underlay,gravel dry underlay,boulder wet underlay,and fine sand vegetation.Underlying surface,underlying surface covered by fine sand vegetation,underlying surface covered by medium sand vegetation,underlying surface covered by humid clay soil,underlying surface covered by wet clay soil,and underlayed by clay ridge vegetation.(2)In the mining area,the roughness of the underlying surface covered by vegetation is larger,and the roughness of the exposed surface is smaller.The relationship between the sand velocity of different underlying surfaces and the roughness is positive correlation;In the mining area,the average sand dust level of the underlay surface with low coverage of fine sand vegetation,the underlay surface with coverage of fine sand vegetation,the dry underlay surface with gravel and the dry underlay surface with breccia crust is relatively large,It is the main type of underlying surface for dust control in the mining area.The dust control of the whole year should increase the prevention and control of the dust transport from February to July,and the prevention and control should also be strengthened for the areas with high mining intensity in the mining area.At the same time,the prevention and control of the dust in the places where the slag and soil are piled up and the coal transportation roads should be increased.(3)The wind sand flow structure of each underlying surface is mainly in the decreasing relationship of power function and exponential function.There are some differences between the wind sand flow structure of the underlying surface which is directly and indirectly affected by coal mining,the sand on the indirectly affected underlying surface is mainly concentrated at 20 cm and 50 cm,and the proportion of sand and dust on the directly affected underlying surface is relatively large at 100 cm and 150 cm.Therefore,the sand and dust transport with higher layer height should be considered in the dust control of mining operations.(4)The proportion of each underlying surface in 0～50um,50～100um,100～250um,250～500um and 500～1000um particles decreases step by step.The overall content of sand and dust on the underlying surface directly affected by mining in the mining area is relatively low,mainly 0～100um sand.With the increase of height,the relationship between the average size of sand particles on the surface and each height layer becomes worse and worse.With the increase of height,the sorting coefficient is better.The size of the skewness,and kurtosis values at 20 cm is basically the same as that on the surface.It shows that the source of sand dust on the sand collector increases with the increase of height,and the impact of industrial mining will also affect the differentiation rule of sand dust size. |
