Research On The Pollution Effect Of Coal Gangue On Loess In Xishan,Taiyuan

There are many coal mines in the Xishan area of Taiyuan,and the coal mining time is long.The coal gangue produced takes up a lot of land resources.With the improvement of the ecological environment in the Xishan area,some sites contaminated by coal gangue have been re-used for engineering construction.At present,most of the research on coal gangue is mainly focused on the release of trace toxic and harmful elements in coal gangue and the enrichment of these toxic and harmful elements in soil and water,and there is no impact on the macro-physical mechanics of soil before and after being polluted by coal gangue.This article mainly takes the coal gangue and the loess around the gangue pile in the Xishan mining area of Taiyuan as the research object.Through X-ray fluorescence spectrum analysis,scanning electron microscopy energy spectrum analysis,indoor geotechnical experiment and dynamic leaching test,combined with previous studies,the coal gangue is analyzed.The main pollutants in the loess,the macro-physical and mechanical properties and microstructure changes and pollution mechanism of the loess contaminated by coal gangue are obtained.At the same time,the migration of coal gangue pollutants in the vertical direction of the loess is studied by the HYDRUS-2d/3d simulation software.The main conclusions are as follows:（1）The content of pyrite（Fe S₂）in the gangue of Xishan Guandi Mine in Taiyuan is relatively high,and the Fe and Mn elements in the gangue are greatly reduced under the effect of weathering.Compared with unpolluted loess,the content of Fe,Mn and S in the loess around the gangue pile increased,while the content of Na,K,Ca,Mg and P all decreased.（2）After the loess is polluted by coal gangue for a long time,the pores become more and larger,the skeleton unit body changes from agglomerates to single particles,and the connection form between the unit bodies changes from cementation to point contact.According to the quantitative analysis of Image-Pro Plus software,the pore size of contaminated loess increases with the decrease of the distance from the gangue pile.（3）After being polluted by coal gangue,the void ratio,density and dry density of loess physical property indicators increase,the content of clay particles,liquid plastic limit,and plasticity index decrease,while the proportion of soil particles remains unchanged.Through the confined compression test,it is found that the compressibility of the contaminated loess decreases,the compression modulus increases,and the compactness of the contaminated loess becomes better.Analysis of the results of the direct shear test found that the cohesive force of the contaminated loess decreases and the internal friction angle increases.（4）Because loess contains a certain amount of carbonate,organic matter and clay particles.Loess has a strong ability to adsorb and remove H⁺and heavy metal ions released from weathering of coal gangue,and can limit the impact of coal gangue pollution to a certain range.The influence of coal gangue on the properties of loess is mainly caused by the H⁺and heavy metal ions produced by weathering.The main way is to thin the electric double layer of the clay particles and destroy the carbonate cement between the particles.（5）HYDRUS-2d/3d software simulates the migration of Mn released from coal gangue in the vertical direction of the loess.It shows that Mn migrates to a depth of 1.0m in the 1.5th year;and in the 4.5th year,the loess within the depth of 1.0m affects Mn.The adsorption reached saturation.