Coal Gangue Particle Suspension Study With High-Concentration Cemented Backfilling On Coal Mine

Based on the project of high concentration cemented backfilling in Linxi Coal Mine,the suspensibility of gangue particles in high concentration cemented backfilling slurry was studied.This paper establish the mechanical models of spherical gangue particles and cubic gangue particles to reveal the principle of the coal gangue particles considerate the coal gangaue weak suspensibility and easy sinking of gangue particles in high-concentration cemented backfilling slurry on coal mine.The settlement law of gangue particles in high-concentration cemented backfilling slurry on coal mine was analyzed and the key factors that affect the suspension of gangue particles were summarized.Based on the fact that the suspension agent was employed to improve the floatability of gangue particles in slurry pipeline transportation,two methods to adjust the suspensibility of gangue particles in high concentration cemented backfilling slurry are put forward.the minimum yield stress range of slurry in suspension of gangue particles in high concentration cemented filling slurry in Linxi Coal Mine is deduced.Through rheological experiments,the impacts of increasing the content of fine-grained material and adding suspension agent on the suspensibility of gangue particles in high-concentration cemented filling slurry of coal mine were explored,the resistance value of pipeline transportation of high-concentration cemented filling slurry of coal mine was estimated,the causes and formation conditions of suspension of gangue particles in high-concentration coal mine slurry were summarized,and the composition of slurry and suspension agent were revealed to improve the suspension of high-concentration slu With the aid of ANASYS Fluent software,the transportation of filling slurry in Linxi Coal Mine was simulated,and the scientificity of the research results was verified.The main conclusions are as following:(1)Coal mine high concentration cemented filling slurry characteristics;Coal mine high concentration cemented filling slurry belongs to a typical non-Newtonian Bingham body flow pattern,with a certain thixotropy.Fine particles in high concentration slurry form a certain structure through physical and chemical reactions.In the process of solid-liquid conversion of high concentration slurry in coal mine,the internal structure of slurry must be overcome first.The larger the slurry concentration,the stronger the internal structure and the more difficult the movement of particles in slurry.(2)Suspension characteristic analysis and mechanical model of gangue particles in high-concentration cemented filling slurry of coal mine;mechanical model of spherical and cubic shape of gangue particles was established to analyze the sinking law of gangue particles in high-concentration slurry.It is considered that the minimum yield stress required for high concentration cemented filling slurry with 76.0%-80.0%mass fraction to realize suspension of gangue particles should be between 165.33-196.11 Pa.The most effective way to adjust the suspension of gangue particles is to improve the yield stress and apparent viscosity of high concentration cemented filling slurry.There are two ways to improve the suspension of gangue particles:increasing the yield stress of high-concentration cemented filling slurry and increasing the medium resistance of slurry;increasing the apparent viscosity of slurry of high-concentration cemented filling slurry and reducing the settling speed of gangue particles.(3)Study on the relationship between fly ash and cement content of high concentration cemented filling slurry and suspension characteristics of gangue particles.The content of fly ash and cement can improve the rheological parameters of high concentration cemented filling slurry in coal mine.When the high concentration cemented filling slurry is low,the yield stress of the high concentration cemented filling slurry decreases as a whole with the increase of fly ash content,but the apparent viscosity of the slurry increases gradually.When the mass fraction of high concentration cemented filling slurry in coal mine is high,the yield stress and apparent viscosity of slurry increase with the increase of fly ash content.With the increase of cement content,the yield stress and apparent viscosity of high concentration cemented filling slurry in coal mine increase.Increasing the content of fly ash and cement in high concentration cemented filling slurry in coal mines can improve the suspensibility of gangue particles and increase the resistance of slurry pipeline transportation.As a result,the transportation distance of slurry pipeline is limited,and it is difficult to meet the requirements of "long distance" and "large flow" of coal mine filling.(4)The influence of suspension agent content on suspensibility of gangue of high concentration cemented filling slurry in coal mine.The suspension of gangue particles can be improved by adding suspension agent in high concentration cemented filling slurry of coal mine.The suspension agent can improve the suspension of gangue particles by increasing the apparent viscosity of the slurry of high concentration cemented filling slurry of coal mine.Increasing the apparent viscosity of slurry,increasing the viscous resistance of gangue particles during settling,slowing down the settling speed of gangue particles,prolonging the settling time of gangue particles,so as to improve the suspension characteristics of gangue particles.Suspension agent has little effect on the yield stress of high concentration cemented filling slurry in coal mine,and has limited effect on the change of slurry pipeline transportation.Therefore,the suspension state of gangue particles can be improved by adding suspension agent,which meets the requirements of "long distance" and "large flow" of coal mine filling.(5)Pipeline transportation numerical simulation of high concentration cemented filling slurry in coal mine;Comparing theoretical calculation results and numerical simulation results,and combining with fluidity test,it is determined that R-T-2 group with mass fraction of 77.0%should be used to prepare high concentration cemented filling slurry in Linxi Coal Mine.At this time,the amount of suspension agent is 0.3%of the total slurry mass,and the simulated value of resistance loss of straight pipe transportation of the slurry in coal mine is determined.4.7 Kpa/m.The numerical simulation results also show that the suspension of gangue particles can be improved by increasing the content of fine-grained material of high-concentration cemented filling slurry in coal mines,but it also leads to the increase of slurry pipeline transportation resistance and the limitation of slurry pipeline transportation distance.Suspension agent has little effect on the yield stress of high concentration cemented filling slurry in coal mine,and has limited effect on the change of slurry pipeline transportation.Therefore,the suspension state of gangue particles can be improved by adding suspension agent,which meets the requirements of "long distance" and "large flow" of coal mine filling.