| Paste filling mining is an important part of green mining,which is one of the effective ways to solve the damage of surface environment and improve the safety of working face.In recent years,due to the rising unit price of traditional paste filling auxiliary material fly ash and the poor filling effect,this thesis uses gangue powder instead of traditional auxiliary material fly ash to explore the difference between mechanical properties and flow characteristics of gangue powder in the case of full substitution,partial substitution and non-substitution of fly ash,and selects the optimal three groups of ratios for filling mining simulation to compare the filling effect of the improved paste.The conclusions are as follows :(1)The physical characteristics and chemical elements of gangue powder and fly ash were compared and analyzed.The analysis shows that the oxide content of fly ash is higher than that of gangue powder,but the particle size distribution and specific surface area of gangue powder are smaller than those of fly ash,and it has good adhesion,indicating that gangue powder has the characteristics of being used as an auxiliary material for paste filling materials.(2)Through the slurry fluidity test results,it can be found that under the same ratio,the number of groups of gangue powder slurry to meet the test requirements is more than that of fly ash slurry;the influence of fly ash on the fluidity of slurry is greater than that of gangue powder.The increase of the amount of auxiliary materials will increase the fluidity of the slurry,but the excess will affect the fluidity of the slurry;gangue powder has better adsorption than fly ash,which can better ensure the water retention of slurry.The viscosity and expansion diameter tests of mixed auxiliary slurry and two kinds of auxiliary slurry further confirm that gangue powder is more helpful to improve the fluidity of slurry than fly ash.(3)The results of mechanical properties test show that the gangue powder paste specimen is not easy to demould than the fly ash paste specimen;the increase of the amount of auxiliary materials will increase the compressive strength of the filling body in the short term,but the excessive amount of compressive strength will decrease,and the fly ash auxiliary material has a great influence on the compressive strength.The early strength of the mixed excipient paste specimens was significantly improved after adding fly ash excipients,and the compressive strength gradually increased with the increase of the proportion of fly ash.The results of compressive and flexural tests further confirm that fly ash is more helpful to improve the strength of specimens than gangue powder.(4)Through the analysis of the ’ full stress-strain ’ curve under the optimal ratio of three types of auxiliary materials,it can be found that the failure modes of the three are the same.Among them,the strain value of fly ash and mixed auxiliary materials is about2 %,while the strain value of gangue powder is 2.4 % ～ 2.5 %.That is to say,under the same stress conditions,fly ash and mixed auxiliary filling materials have smaller strains than gangue powder,which can better control surface settlement.The results of the shrinkage of the three show that fly ash > mixed excipients > gangue powder,which is consistent with the test results of the water precipitation rate of the slurry and the setting rate of the test piece,indicating that the paste test piece of the mixture excipient combines the strength advantages of the fly ash paste test piece and the advantages of the fluidity and shrinkage of the gangue powder paste test piece,and has a better filling effect.(5)Through the analysis of overburden rock migration results,roof deformation value results and surface deformation results,it is found that the filling effect of mixed auxiliary filling materials is the best,indicating that the properties of paste filling materials and filling rate are the key factors determining surface deformation. |
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