Abstract: Tailings sand filling technology plays an important role in China′s mining enterprises,but previous studies have focused on the effects of bed height,slurry residence time and flocculant dosage on the underflow concentration,there are few studies on the effect of adding coarse tailings particles on the properties of underflow slurry in vertical sand bin.Therefore,three types of coarsegrained tailing sand were selected and the effect of the addition of coarsegrained tailing sand on bed settling velocity,bottom flow concentration and slurry rheology was analyzed.The results of static thickening test show that the evaluation value of thickening effect can be improved under suitable flocculation conditions,and the optimal flocculant dosage increases with the increase of flocculant concentration.The bed settling velocity and underflow concentration increase with the increase of coarse particle addition and the lifting effect of coarsegrained tailings in the range of -2 000 μm is more obvious.The dynamic thickening test results show that the average concentration of the underflow slurry is positively related to the bed height,slurry residence time and the amount of coarse particles added,the static yield stress and dynamic yield stress of the underflow slurry both decrease with the increase of coarse particles content and increase with the slurry concentration,which provides reference for the stable operation of the underflow of the vertical sand bin with high concentration.

Key words: tailings sand filling,vertical sand bin,underflow concentration,coarse particles,yield stress