Ann: Bellevue Resource Increases to More Than 1.5M Ounces of Gold, page-61

Agreed with Bogun, 

High grade pillars are generally recovered by using stope support such a paste (fine tailings and some cement being one method) then mining the pillars. Flat lying stopes require more support as you would expect and if the wall are competent vertical stopes can be left open with all ore removed between levels etc. Each stope will be assessed for stability,  mining and support methods designed. The greater the volumes mined out the more stress it causes on the surrounding rock and these days a lot goes into rock mechanics and the safe but economical extraction or ore.