| Cemented filling mining is an important part of green mining,which can absorb solid wastes such as gangue and fly ash on a large scale and control mining subsidence significantly.But at present,the pipeline transportation resistance loss of filling slurry with gangue as aggregate is large,and it depends on pumping in most conditions,resulting in high equipment investment and frequent pipe plugging accidents.Inspired by the solid composition characteristics of aeolian sand paste like slurry with superior fluidity,the idea of optimizing solid composition to improve slurry fluidity and reduce pipeline resistance loss is proposed.This paper analyzes the influence of different combinations of aggregate(aeolian sand and gangue)and powder(fly ash,cement,quicklime,etc.)on the fluidity of filling slurry by establishing the mechanical model of aggregate particle suspension,static water settlement test,slurry fluidity test and slurry rheology test,and puts forward the optimization of the design method of pipeline diameter.The main conclusions are as follows:(1)The test of physical properties of common solid materials of coal mine filling slurry shows that the particle size of fly ash,cement,quicklime and other cementing materials is generally less than 0.1 mm,which is called "powder" relative to gangue and aeolian sand aggregate.The powder particles form a "floc net structure" in the water,which improves the medium resistance of the aggregate particles and forms the suspension of the aggregate;Aggregate particles destroy the force between fine particles and weaken the "floc net structure".It is proposed that the suspension of aggregate particles is one of the indexes to evaluate the transportation state of filling slurry in pipeline.(2)The mechanical model of suspension of aggregate particles in Bingham slurry was established,and the influencing factors and expressions of settlement resistance,final settlement velocity and maximum non settling particle size of aggregate particles were obtained.The suspension state of spherical particles(Group)and irregular particles(Group)in slurry was analyzed.The results show that the larger the particle size,the more irregular the shape and the more the quantity of the aggregate,the greater the yield stress of the slurry required for suspension.(3)Based on the static water sedimentation test,slurry fluidity test and rheological test of solid particles,it is concluded that gangue particles with different particle sizes present different characteristics in slurry,and fine gangue particles below 0.315 mm have similar characteristics to cement and fly ash,which can be used as powder,It provides a new way for underground filling and disposal of gangue;The fluidity of coarse-grained gangue slurry increases with the increase of particle size under a certain particle size,but when the particle size increases to a certain value,the slurry will segregate and bleed.The results show that the best fluidity can be achieved only when the maximum particle size of gangue aggregate is reasonably matched with the properties of mortar.(4)The results show that the static water settlement velocity of gangue particles under 0.315 mm is small,and the slurry is homogeneous and has a large fluidity,which is similar to cement and fly ash.Therefore,it is considered that 0.315 mm is the particle size limit of gangue particles as powder or aggregate.Based on this,the coarse and fine mixed pure gangue gypsum(concentration 80%)filling materials are developed.By reducing the maximum particle size of gangue aggregate,the fluidity of slurry is improved,the requirements of pumping pipeline transportation are met,and a new way is provided for underground filling and disposal of gangue.(5)The "multiple method" is put forward to calculate the resistance loss per unit length of elbow.The multiple relationship between the local loss per unit length of gravity slurry and the resistance loss along the way is measured through experiments,which enriches the design theory of slurry conveying pipe diameter. |
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