Research On The Composite Ash Filling Material Blending Coal Gangue And Flue Dust With The Superhigh-water Material

Mining with filling in mine is one of the best way to solve the problem of coalminingunder buildings,railways and confined waterin our country.After nearly30yearsdevelopment, the technique of mining with filling undergos several stages as waste fill,sandfill,concrete-cemented fill,fine sand-cemented fill,waste rock-cemented fill,high concentration oftailing fill,paste fill and the superhigh-water material fill.The superhigh-water material is oneof mine filling materials developed by China University of Mining and Technology.It has suchadvantages as rapid hardening,good fluidity with single slurry,adjustable initial setting timeand so on.Its hardening body is not shrinkable,little volumetric strain and goodincompressibility under triaxial compressive condition.It’s the perfect filling material forsolving the problem of coal mining under buildings,railways and confined water andimplementing of green mining.Solid waste accumulation caused by coal mining and utilization are more and moreuniversal and form a number of waste dump,flue raise dust,which causes seriousenvironmental pollution.Composited these solid wastes with superhigh-water material for coalfilling can improve the environment,meanwhile can also reduce the cost of thesuperhigh-water material.The basic characteristic of coal gangue and flue dust as the aggregate of thesuperhigh-water material was first studied in this paper.The factors influencing slurryformation of suitable concentration by coal gangue and flue dust were investigated,and thebest transportation condition of aggregate slurry was obtained.The results show that the originof coal gangue and flue dust,ratio of flue dust to coal gangue,water temperature,massconcentration of slurry,graded composition of coal gangue and so on,all have influence on theviscosity properties of slurry.According to the significance,the order of all influening factorsare respectively:mass concentration of slurry> ratio of flue dust and coal gangue> gradedcomposition of coal gangue> temperature> origins of coal gangue and flue dust.Theinfluence of chemical composition and mineral composition of coal gangue on the aggregateslurry related to the corresponding metamorphic grade of coal,the higher of the correspondingmetamorphic grade of coal,the lower influence of the chemical composition and mineralcomposition of coal gangue to the aggregate slurry.At the same time,the suitable parametersfor slurry transportation are:water temperature20℃,particle size distribution of coal gangue0-6mm,gangue origin XZJH,flue dust origin2#,ratio of flue dust to coal gangue1:1or2:3,and the mass concentration of slurry corresponded are72%～74%or76%～77%. Then,the viscosity properties,initial setting time and uniaxial compressive strength of thecomposite material were studied that made from the superhigh-water material mixed with coalgangue and flue dust in certain proportion.The result shows that the influence factors ofviscosity properties and initial setting time of mixed slurry according to the significant orderare ratio of water to superhigh-water material> ratio of flue dust to superhigh-water material>water temperature> ratio of flue dust to coal gangue.But the four factors only affect theviscosity of the composite slurry and have no influence on the viscosity change of mixedslurry with time.The viscosity of the composite slurry has little change with time at thebeginning,but about20min before the initial setting time,it increased quickly and achievedinitial setting during a short time.The initial setting time and the uniaxial compressive strength of this material at suitablepropotion are also investigated here,the result shows that reducing the ratio of water tosuperhigh-water material and the ratio of flue dust to coal gangue or increasing ratio of fluedust to superhigh-water material could increase the strength of solidified body of thecomposite material;reducing water content or increasing the dosage of superhigh-watermaterial could improve the strength of the solidified body.Too much flue dust dosage wouldreduce the strength of solidified body.The strength of solidified body was gradually increasingwith time,but the increasing range would be more and more small,and the strength ofsolidified body would gradually stabilize when time achieved28d or later.Considered the requirements of actual mining filling,obtained the best proportion of thesuperhigh-water ash filling material are:ratio of water to superhigh-water material6:1,ratio offlue dust to superhigh-water material5:1,ratio of flue dust to coal gangue2:3,watertemperature20℃,that is,the percentage of the actual material about water,superhigh-watermaterial,coal gangue and flue dust respectively are30.77%,5.13%,38.46%and30.77%.Andcompared with the same ratio of water to superhigh-water material of the superhigh-watermaterial,acquired that per unit volume of the superhigh-water ash filling material could saveapproximately44.73%of the superhigh-water material.