Experimental study on the natural mixing behaviour of waste rocks poured in a paste backfill

ABSTRACT

Underground produced waste rocks (WR) are typically hoisted and stored on the ground surface as WR piles. The practice requires energy consumption for transporting the WR from underground to ground surface and generates additional operation costs. An alternative practice is to directly pour the WR into mine stopes being filled with paste backfill. However, the natural mixing behaviour of WR poured in a paste backfill has never been studied. To fill this gap, a series of physical model tests have been performed for the first time in the laboratory to understand the natural mixing behaviour of WR and paste backfill. The definitions of solids content by mass of WR and mixing degree are for the first time proposed to quantitatively evaluate the mixing behaviour between the poured WR and paste backfill. The test results show that the penetration of waste rocks into paste backfill and mixing degree can be improved through the use of paste backfill of low solids content, large particle sizes of waste rocks and/or through the increase of falling height of poured waste rocks. The proposed definitions can be used as good indicators to quantitatively evaluate the mixing quality of the natural mixture.