As the Grasberg open pit is completed in 2019, the underlying Grasberg Block Cave (GBC) will rapidly mature as a primary source of production at PT Freeport Indonesia operations, supplementing the Deep Ore Zone (DOZ) and Deep Mill Level Zone (DMLZ) caves. After years of planning, development and revisions to the extraction strategy, early information on footprint rock mass response to undercutting and the nature of caving is now available to confirm or guide adjustments to strategy. Despite the early stage of mining, much has been learned regarding cave propagation, fragmentation, stress states, pillar stability and ground support performance. This paper provides a timely rock mechanics focused update from one of the largest planned caving mines in the world.

At PT Freeport Indonesia's Grasberg mining complex, the Grasberg open pit is scheduled to cease production in early 2019. Mining of the Grasberg deposit will then transition to the underlying Grasberg Block Cave (GBC) mine, with initial undercutting currently planned for late 2018. The GBC is projected to become the district's flagship underground mine for the next two decades. Early-stage production areas at the GBC are hosted within a heterogeneous rock mass. The footprint will be subjected to variable abutment and cave loading conditions. Mine design and sequencing adjustments, combined with customised ground support options, continually evolve to improve footprint reliability and permit a favourable transition between open pit and underground operations. This paper provides a snapshot of strategies employed to promote the successful caving operation at the GBC mine.