西北干旱荒漠区典型露天煤矿不同下垫面风沙流特征

Aeolian sand flow on different underlying surfaces of typical opencast coal mines in the arid desert region of Northwest China

为揭示西北干旱荒漠区露天煤矿风蚀特征,选取该区域内具备代表性的典型露天矿区,对其不同场地下垫面进行分析,通过野外实地监测,分析了矿区不同下垫面风沙流特征。研究结果显示:随高度增加,块石植被低覆盖干燥(RLd)下垫面风沙流输沙量垂向特征表现为先依次递减后增加,其余下垫面则总体表现为随高度增加而减少;0.2 m为风沙流的主要输移层,砾石覆盖度、植被覆盖度与地表湿润度的增加,会有效降低风沙流水平通量。近地表土壤结构受大型机械循环作业活动变的疏松、风蚀物质粒径减小,同时因自身地表干燥,研究区近地表土壤风蚀可蚀性增加;水平通量在风季时期因人为干扰作用,沙尘加快了运移。在车工机械的影响下,矿内生产活跃区下垫面风沙流空间结构特征较其他下垫面出现向高层偏移的现象,主要开采区域风蚀程度严重,且人为干扰程度越强,偏移现象越明显。矿区周边沙地下垫面水平通量较大,地表可风蚀性质较强,受研究区盛行风及人为采矿导致地表凹陷等因素影响,该区域是矿区大粒径风蚀物质的主要来源地。因地表湿润度与植被覆盖度的增加,部分下垫面风沙流结构最优关系式为指数函数的形式,表现为随高度增加输沙量变化较急剧,其余下垫面风沙流结构最优关系式函数类型为幂函数。矿内主要开采活跃区下垫面的输移物质主要为极细粉沙,且主要粒径组风蚀物影响范围超过1.5 m,是造成露天矿区能见度下降的主要原因。研究成果可为西北干旱荒漠区露天矿区沙害防治提供理论依据和科技支撑。

The underlying surface can be closely related to the atmospheric movement near the land surface.It is also a primary determinant of soil wind erosion,particularly for the mining environment restoration.One of the most important cities for opencast coal mining,Wuhai City in Inner Mongolia of China is located in the arid desert areas of the northwest with the violent surface sand movement.It is a high demand to reveal the features of wind erosion for the typical underlying surface in this study areas.In this study,a systematic investigation was made to classify the different underlying surfaces for the features of aeolian sand flows in the mining areas via field monitoring.The results showed that the underlying surface of the opencast coal mines was divided into 12 categories,according to the features of surface particulates,vegetation coverage,and surface wetness.With the increase of height,the vertical characteristics of aeolian sand flow and sediment transport on the underlying surface of rocky vegetation with low coverage and dryness(RLd) showed that it first decreased and then increased,and the rest of the underlying surface generally showed a decrease with the increase of height;where the 0.2 m depth was the main transport layer of wind-sand flow.There was an increase of gravel coverage,vegetation coverage and surface wetness,whereas,the decrease in the horizontal flux of sand flow at the site.Affected by large-scale mechanical circulation operations,the near-surface soil structure becomes loose,and the particle size of wind-eroded substances decreases.At the same time,due to its own surface drying,the wind-erodibility of the near-surface soil in the study area increases;dust accelerates migration.Under the influence of turning machinery,the spatial structure characteristics of the wind-sand flow on the underlying surface in the active production area in the mine shifted to the high-rise compared with other underlying surfaces.The wind erosion in the main mining area was severe,and the stronger the degree of human interference,the migration phenomenon.more obvious.The underlying surface of the sand around the mining area has a large horizontal flux,and the surface is highly wind-erodible.It is affected by the prevailing wind in the study area and the surface depression caused by artificial mining.It is the main source of large-sized wind-eroded materials in the mining area.Due to the increase of surface wetness and vegetation coverage,the optimal relationship of aeolian sand flow structure on part of the underlying surface is in the form of an exponential function,which shows that the amount of sediment transport changes sharply with the increase of height,and the optimal relationship between the other underlying surface sand flow structure function type is a power function.The transported material on the underlying surface of the main active mining area in the mine is mainly ultra-fine silt,and the influence range of the main particle size group wind erosion is more than 1.5 m,which is the main reason for the decrease of visibility in the opencast mining area.Therefore,the finding can provide a theoretical reference and technological support for the sand prevention and control in the opencast mines in the arid and semi-arid areas.