Abstract: A method for forming a passage in stope backfill material includes steps of: a) providing an expandable void forming apparatus at a lower level relative to an unexcavated stope; b) expanding the void forming apparatus, such that a substantially liquid-impermeable seal is formed between the void forming apparatus and the unexcavated stope; c) pouring backfill material into a void formed by the excavation of a stope adjacent to the unexcavated stope, and allowing the backfill material to at least partially cure such that the void forming apparatus forms a passage between the unexcavated stope and the backfill material; and d) contracting the void forming apparatus and removing the void forming apparatus from the passage.