The Sugar Zone and Middle Zone mineralization typically comprises tabular, narrow veins, approximately 1.5 m to 3 m thick, and dipping at around 70° to the southwest. Excessive dilution is potentially a major risk to operating success in narrow mineralization. Longitudinal longhole retreat stoping was selected as appropriate for this Deposit based on the favourable geometry, current geotechnical knowledge and success of the Bulk Sample trial mining. Both the ore and the host rock are sufficiently competent to facilitate the void sizes required for effective longhole stoping.
The longhole open stoping mining method provides the following advantages:
- Safe – personnel do not enter the production mining voids (remote-controlled equipment only).
- Proven – many instances of the methods application throughout the world.
- Highly mechanized – reduces personnel exposure to health and safety risks.
- Easy access to resources – skilled labour and equipment are readily accessible locally and around the world.
- Low cost – leverages off large drill and blast scale and minimization of development.
Empirical stope stability analyses by RockEng concluded that, for typical conditions, stopes are expected to perform well:
- Stress in the major influence on stability variability:
-- Above 200 m mining depth stress conditions are favourable (A factor is 0.8–1.0).
-- Between 200 and 500 m mining depth is a transition zone.
-- ........
