Granny Smith gold mine - Mining
The current operations consist of the Wallaby underground mine with mining occurring on four ore zones (Z70, Z80, Z90 and Z100), which form the basis for the 2018 operational plan. Current decline development has passed Z110 and will reach Z120 during 2018. Development ore from both Z110 and Z120 is scheduled as part of the 2018 mine plan, with stoping commencing in 2019.
Mining methods
Access to the Wallaby underground mine is via a portal established within the completed Wallaby open pit. The mine operation is trackless, with truck haulage from underground via the pit ramp to the surface. The Wallaby underground mine is currently designed to exploit lodes to a depth of 1.2km.
Two primary underground mining methods are used, with minor adjustments to suit localised geometry. Inclined Room and Pillar (IRP) is used in areas with a moderate dip (10° to 35°) and moderate width zones (4m to 6m), and transverse long-hole stoping (TLHS) is used in zones, which are thicker (6m to 15m) with variable dips. Two other mining methods are used to a lesser extent: narrow vein long-hole stoping may be utilised in some areas with the benefit of reduced planned footwall dilution, and bulk long-hole stoping is used in thicker zones (15m plus) under varying dip conditions.
Mine planning and scheduling
At Wallaby, the mine design takes practical stope layouts into consideration, as well as planning for mining losses in barrier pillars and stope pillars, or other parts of the resource excluded for geotechnical, accessibility or economic reasons.
The production scheduling uses rates based on historical mining performance. Geotechnical controls, ventilation requirements and production cost management remain focus areas for margin protection as mining progresses to greater depths.