| Over the past three decades,there have been a large number of ecological restoration and land reclamation projects in coal mining areas in my country,and the phenomenon of soil reconstruction due to the remodeling of geological and landforms is relatively common.In order to effectively simulate the water movement and gas diffusion process of the reconstructed soil profile,it is of great significance to accurately measure the soil hydraulic parameters,gas conductivity and gas diffusion rate.The thesis takes the reconstructed soil of Lianghuai mining area as the research object In the laboratory,the water content,saturated hydraulic conductivity,water characteristic parameters,air conductivity and gas diffusivity of different substrates and reconstructed soil are measured and analyzed.Analyzing and studying the characteristics of water and gas movement parameters and their influencing factors,providing basic data for simulating and reconstructing soil water movement and gas diffusion,and then provide references for environmental restoration problems in coal mine areas,and optimize field management measures similar to ecological restoration areas,the main conclusions obtained in this article are as follows:(1)The gas diffusion coefficient and gas conductivity of the mean filling medium have a negative correlation with the water content.The gangue gas conductivity has the largest difference,while the gas diffusion coefficient has the smallest difference as the water content changes.The gas diffusion coefficient of clay varies the most with water content.Under the same water content dimension,the air permeability of silty clay loam is the lowest,even lower than clay.The gas diffusion coefficient of the those filling media is clay<silty clay loam<coal gangue.Among the those filling media,the clay has the highest water suction,while the water in the silty clay loam is more likely to flow out with the increase of pressure in the experiment,which causes the clay to have a lower hydraulic conductivity than silty clay loam.(2)The mixture of coal gangue,silty clay loam and sandy loam can improve the pore distribution and structure of coal gangue,reduce the generation of large pores,enhance its water holding capacity,and reduce the cumulative infiltration.At the same time,the permeability of the mixed matrix can be improved,and the mixing of silty clay loam and coal gangue is the most effective to improve the performance of coal gangue.The addition of silty clay loam can also reduce the cumulative infiltration and saturated hydraulic conductivity of coal gangue.(3)The saturated hydraulic conductivity of reconstructed layered soil is easily affected by bulk density and soil texture.Both bulk density and soil texture indirectly affect the saturated hydraulic conductivity of soil through porosity.The larger the bulk density of the reconstructed layered soil,the smaller of its saturated hydraulic conductivity.No matter what kind of reconstruction relationship,it shows that the soil bulk density has a negative correlation with the saturated hydraulic conductivity of the reconstructed layered soil.The way in which soil texture affects layered soil is more complicated.The topsoil texture and the hydraulic conductivity of the underlying surface matrix jointly affect the saturated hydraulic conductivity of reconstructed layered soil.(4)The air permeability of reconstructed layered soil is basically not affected by the bottom filling medium,but is related to the surface soil.The response of the reconstituted layered soil to the water content is also not affected by the bottom filling medium.Under the same water content,the air conductivity of the top soil plays a key role.At the same time,silty clay loam covered with coal gangue improves the permeability of reconstructed soil and increases gas exchange between the soil and the near-surface atmosphere.Figure[22]Table[14]Reference[87]... |
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