Abstract

Sublevel caving (SLC) method has a number of features that make it one of the preferred methods for high productivity and early access to ore recovery. However, major challenges associated with this method are ground surface subsidence and high unplanned ore dilution due to the collapse of the overlying strata. To remedy these shortcomings, a recent approach has been to modify the SLC method by introducing backfill (waste rock) into the void atop the production zone to provide continued support of the stope and prevent the host rocks from caving in.

In comparison to other long-hole stoping methods, predominantly practiced in Canadian mines, the Modified SLC method boasts several advantages. Early production achieved from the topmost level helps reduce the payback period. Productivity is enhanced due to the benefit of multilevel mining without the use of sill pillars and its associated recovery challenges. The cost of backfilling the stopes is significantly reduced as there is no need for the construction of paste-fill plants and its associated operational cost and challenges. Continuous stoping is achieved without paste-filling delays as mining and backfilling take place concurrently. A significant reduction in underground development costs is achieved as fewer slot raises and crosscuts are required for stope readiness.

This study, therefore, highlights the merits of the Modified SLC method in steeply dipping tabular and wide orebodies by ways of reference to real-life mine case study. Dilution issues are addressed. The benefits of top-down mining are explained, and typical mining schedules are presented to demonstrate productivity. Geomechanics issues associated with different in-situ stress environments are discussed and illustrated with simplified mine-wide numerical modeling.