REVIEW OF CURRENT HIGH DENSITY PASTE FILL AND ITS TECHNOLOGY

Backfilling techniques are widely used in large-scale underground mines. Massive pillars, which have been left in place for stability, limit mining activity. Backfilling allows for safe recovery of the ore remaining in pillars and assures long-term stability. The high rock stresses which result from deep mining operations can be relieved by backfilling. Initially, waste rock was used to fill the openings left by mining operations, though with mixed results. The need to improve safety and reduce costs has prompted the mining industry to investigate alternative backfill methods. Hydraulic filling with Portland cement has shown considerable promise, but little has been done to define the parameters for an effective design. The objective of this paper is to enhance the understanding of current paste backfill practice. Sixty to seventy weight-percent solids-cemented backfill slurries are currently being used in the mining industry (as a matter of practicality). However, deficiencies in this particular ratio need to be examined. Physical properties of mine tailings are unique based on their geology and the milling process. Flaws in the cemented backfill slurries are usually a result of poor hydration and slime build-up to levels that cause additional dewatering, high equipment/operating costs, and work delays. Furthermore, the required strength and quality of the fill may be affected by high water-cement ratios, as well as by its consolidation time, permeability, and volume changes.