Hydraulic Backfill Consolidation in Underground Mine Stopes

This paper highlights the importance of considering hydraulic backfill consolidation and wet arching when determining the stresses in underground mine stopes and acting on the barricade. The wet arching is introduced here as an arching effect during consolidation. Most studies consider hydraulic backfill consolidation as an instantaneous process and ignore its effects on stress within the stope and acting on the barricade. Mainly the reasons would be the granular behaviour and higher permeability of mine tailings used for hydraulic backfills. Yet, recent laboratory experiments and tests carried out under this study show that the consolidation is slow enough to significantly affect the hydraulic backfill stresses. According to the literature, hydraulic backfills have a considerable amount of fine particles which can slow down the consolidation process as evident in the tests. The paper discusses available stress variation between dry and wet fills while demonstrating its significance and requirements for further studies in consolidation and wet arching. Another important factor ignored in the literature is the hydraulic backfill property variations which were evident in tests carried out in this study. The results suggest segregation occurs within the fill which follows property variations over depth and considerably influences stresses. These effects must be considered when determining the stresses within the fill and developing a hydraulic backfill stress model.