Preliminary work was performed on four possible mining systems: post-pillar cut-andfill, transverse with pillars, transverse with cemented fill, and sublevel with end slicing.
The post-pillar cut-and-fill mining method was selected for the PEA evaluation.
This mining method relies on using 5 m x 5 m rooms and 5 m x 5 m square pillars. The pillars of one level are planned to align vertically with the next mining level to provide support. Mining starts at the lowest elevation in a mining area and is completed working upward. Some pillars can be extracted when they occur in an area of the stope where there will be no mining above.
Productivity calculations and unit costs for the final selection of a post-pillar cut-and-fill mine plan are based on the following criteria:
• Two 10 hr shifts per day, which yield 16 hr of actual work time.
• The ground is considered medium–hard for the drilling and blasting variable.
• Drilling of 18 ft (5.5 m) holes (providing 16.6 ft (5.1 m) of advance) with a two-boom production jumbo. Hydraulic drifter (drill) penetration rate is assumed to be 3.5 ft/min (1.1 m/min).
• No standard ground support is indicated; however, 1.5 hr per cycle is allotted for ground control (e.g. rock bolting), spot bolting or other cycle interruptions.
• Blasting will be carried out using gelatin-class dynamite and ammonium nitrate/fuel oil (ANFO) as the primary blasting agent. Non-electric (non-el) type ........