Study On The Characteristics Of Water And Gas Migration In The Reclamation Land By Coal Gangue And Fly Ash Mixed Filling

China is a big country of coal production and consumption.Land subsidence,coal gangue and fly ash accumulation caused by coal mining and use will cause a series of environmental problems.How to rationally use coal gangue and fly ash to restore the ecological environment of mines has become a hot issue for scholars at home and abroad.Because coal gangue and fly ash are quite different from the physical and chemical properties of soil,the significant difference between the filling layer and the surface soil affects the movement of soil water and gas,which in turn affects the effect of reclaimed land.The current research on the coal ganguefly ash mixed filling mode is less.Therefore,this article systematically measured coal gangue,fly ash,coal gangue-fly ash mixture,soil hydraulic parameters and air conductivity through the indoor simulation test method,and simulated the actual indoor soil column at the same time.The filling situation studies the changes of indicators such as wet front migration and cumulative infiltration,and in-depth discussion of the law of the characteristics of water and gas migration in the soil filled with coal gangue and fly ash.The research provides a reference for the improvement of the land reclamation model in the subsidence area,and at the same time provides a data reference for the practical application of the coal gangue-fly ash mixed filling method.The main findings of the paper are as follows:(1)The physical and chemical properties of fly ash,coal gangue and soil are quite different.Compared with soil,fly ash has better water absorption and water retention,while coal gangue has very poor water absorption and water retention.The saturated water content and saturated hydraulic conductivity of fly ash,coal gangue and soil are all affected by bulk density.The larger the bulk density,the smaller the saturated water content and saturated hydraulic conductivity.Under the same moisture content,the air permeability of coal gangue is much greater than that of fly ash and soil.The air permeability of fly ash,coal gangue and soil decreases with the increase of water content.(2)The hydraulic properties and gas conduction properties of fly ash-gangue mixture are between fly ash and coal gangue.Under different fly ash blending conditions,the higher the blending amount of fly ash,the saturation of the mixture The higher the water content,the lower the saturated hydraulic conductivity and the lower the air conductivity.When the gangue ratio is 3:7～2:8,the saturated water content and effective water content of the mixture are closest to the soil.The saturated hydraulic conductivity of each medium is from high to low,namely coal gangue,fly ash-coal gangue mixture,Fly ash,soil.The saturated hydraulic conductivity of fly ash-gangue mixture is affected by fly ash blending amount and bulk density.Increasing the bulk density under the same fly ash blending amount will reduce the saturated hydraulic conductivity,and the overall trend of the saturated hydraulic conductivity varies with The amount of fly ash added increases and decreases,they were 36.9%～41.3% and 17.3%～17.6%.(3)Compared with the coal gangue filled column,the incorporation of fly ash significantly increases the time required for the wet front of the mixture to move to the same distance,and at the same time increases the cumulative infiltration of the mixture.With the increase of the amount of fly ash mixed,the difference between the wetting front migration time and the cumulative infiltration amount of different gangue ratio mixtures at the same distance becomes smaller.The water content of each layer of the soil column under the filling condition of the mixture of gangue ash ratio of 3:7 is closest to the water content of each layer of the soil column filled with original soil.(4)When coal gangue or fly ash is used to fill the subsidence area,the hydraulic properties of the reclaimed soil will be greatly affected.In the fly ash reclaimed land,the soil shows a situation where the water content becomes larger.The situation is reversed in reclamation,and the water content of the reclaimed soil filled with fly ash-coal gangue mixture is close to the original soil.When filling and reclaiming the land in the subsidence area,the fly ash-gangue mixture with a gangue ratio of 3:7 will have a better effect.The permeability is small and a good plant effective water supply can be ensured.This has great reference value for guiding the improvement of reclamation quality in subsided areas.