Research On The Superhigh-water Packing Material And Filling Mining Technology And Their Application

China is rich in coal resource. But unfortunately, most of them are located undervillages, railroads and surface buildings. The very reason is that most provincesabounding in coal site on the plain with more villages of high population density. Howto mine these coals above is key factor and primary problem restricting thedevelopment of China's coal mining. Green coal mining is the only way to achievesustainable development of China's coal industry. Coal filling mining technology is aprime choice to achieve these goals. In this paper, the project of superhigh-waterpacking material used as mine gob filling material is proposed and obtained a detailedstudy.This paper studied fully about the formation mechanism of superhigh-watermaterial based on detailed inspection of a large number of domestic and foreignliteratures. Through a large number of experiments trial and error on the key elementsto form the superhigh-water material, reasonable constituents to form superhigh-watermaterial were found. It was composed of A and B components together with a smallamount of complex accelerating, retarding agents and dispersant. The setting time ofthe material could be regulated from 8 to 90 minutes. Its compressive strength couldalso be changed under different water content. For instance, when the water volumecontent varied between 95 97%, its final strength could be varied between 0.66 ¹.5MPa. The slurry formed with A or B alone could keep 30 to 40 hours unsetting,whereas the mixture of A and B hardened quickly.In order to investigate the properties of the superhigh-water material, its basicproperties including basic mechanical properties, chemical properties and stabilitywere investigated in laboratory. It was found that the material has quick hardeningcharacteristics and the 7 day compressive strength could be up to 60⁹0% of the 28day one. After that, the strength growing slowed down. Its compressive strength andsetting time could be regulated by adjusting the water-solid ratio and additives. Thesmall bulk strain of this material made it apt to filling application in largeunderground interspace. The material was of poor weathering-resistance property,which indicating that it was not suitable for hot, dry and open-up environment. In thewet conditions of underground goaf, the material could be easy to use, especiallysuitable for filling the large space confined underground.The microtopography of the superhigh-water material induration was investigated by SEM analysis. The results showed that its main ingredient is ettringite. Thisettringite in the superhigh-water material was thin and wire-like, accompanied byAl(OH)₃-gel and other gel-type substances. It was also found that the water volumecontent in 95% is a key point, beyond it, the structure of ettringite was dominant inthin, mesh-like structure. But less than it, the ettringite needle-like structure wasthickening more and more. Therefore, it was appropriate to make the water volume in95% be a turn point from high-water to superhigh-water packing material.Rheology studies of the superhigh-water material showed that the slurry viscosityof A or B alone was almost as small as water's and then could be referred asNewtonian fluid, while the mixed slurry was a time-varying non-Newtonian fluid. Butthe viscosity of the mixture increased slowly in the initial stage. It did not rise quicklyuntil the time kept about two to thirds of the setting time of the material. When nearthe setting time, the curve of the viscosity reached an inflexion. The apparentviscosity at inflexion of the material with short setting time was lower than that of thelonger ones.The hydrodynamic properties of the superhigh-water material such as the criticalnon-silt velocity and so on were studied here with combination with the basicequations of fluid flow and a number of empirical models. It was found that all thefactors such as apparent viscosity of slurry, particle composition, concentration,transporting pipe diameter and other relevant ones had impacts on the hydrodynamicperformance. When the nominal diameter of 100²00mm conventional seamless steelpipe used to transport superhigh-water materials, the conveying velocity should be noless than 2m/s.After detailed study on the properties of the superhigh-water material and thefilling mining methods, it was found that most of the methods were suitable forsuperhigh-water packing material, including open-up filling, bag filling, mixed-typefilling, partition-wall filling and so on. These methods could be selected according toon-site mining techniques used. Open-up filling was simple and no need to set upfilling bags, and the adaptability of the bag filling was better and broader.A semi-continuous filling system suitable for underground filling was developed.It was composed of four subsystem components. A number of mixers ran alternatelyin use, so that the slurry supply could keep continuous to meet the transportrequirement of filling slurry.This superhigh-water packing material had been succeeded in underground goaf filling as its practical application. After a detailed study of the field condition, thesurface deformation of overlying rock was analyzed using the simulation software anda reasonable filling program was proposed. After the goaf filling, the simulation of theground behavior and field theoretical analysis was also carried out, which made thepractice application success in Taoyi coal mine of Handan Mining Group for thickcoal seam. Currently, Taoyi Mine successfully carries out the third working face of thefilling mining. The thin-seam filling mining of Tianzhuang Mine of Linyi MiningGroup has also achieved gratifying results. Now the filling working is progressingsmoothly with a good effect.In order to investigate the effectiveness of goaf filling, strata control observationabout the surface subsidence of Taoyi and Tianzhuang Mine was carried out. Up tonow, the earth surface above the working face has not shown any influence due to thefilling. It is indicated that goaf filling with the superhigh-water packing material hasobvious economic benefits, social and environmental benefits.There are 87 pictures, 33 tables and 198 references in the paper.