An investigation into composite minefill characteristics
9th International Symposium on Mining with Backfill
Ferri Hassani, Alfred Annor,
The history of mine backfill shows that in the past, considerable improvements in backfill-reliant mining technology were made when new fill systems were introduced. The present trend in mine backfill technology is towards the use of high-density fill systems as mines go deeper and ground stresses increase. Tight filling and void reduction have also become essential requirements in engineering design of mines to ensure global stability.
Composite fills are made up of derivatives of waste rock, tailings, sand and metallurgical by-products. As mines go deeper, the ore could be processed partially or fully underground, and the waste rock and tailings combined together to form a low-porosity competent fill product. The application of composite fill systems will also increase the material available for backfilling, provide more flexibility in backfill mix design and produce competent fill systems for ground support. It will also benefit the underground mine environment through effective utilization of mine wastes. This will contribute in reduction of mine waste deposition on the surface.
Several types of cemented backfill were investigated for unconfined compressive strength, deformation modulus and porosity. The materials consisted of total tailings from two precious metal mines, alluvial sand and waste aggregates combined with 5 to 6% Portland cement in various combinations. A new concept of backfill, namely, composite minefill which consists of a mixture of fine tailings and graded coarse aggregates was introduced and the material properties were investigated. It was found that this type of backfill resulted in the lowest porosity of all investigated mixtures while attaining strength in excess of 1 MPa in 7 days.