Palabora

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Palabora mine[1]

Palabora is an underground copper mine in South Africa that uses the block caving mining method. Rio Tinto successfully transitioned Palabora from an open pit mine to underground block caving in late 2004. In 2005, the mine achieved its targeted production capacity of 30,000 metric tonnes ore per day at an average grade of 0.67% Cu (Fiscor). The mine employs approximately 2,200 workers. [2]

Details of the undercut design, production design, equipment, mine access, and ventilation at the Palabora Mine are provided below.

Undercut Design

The undercut is designed 460m below the ultimate open pit bottom (1200 m below surface). The drifts are narrow with a height of 4 m. The undercut is developed before opening the drawbells to create a “stress shadow”. Resin grouted bolts, mesh, and shotcrete are used as support. [2]

Production Design

The production drift occurs 18 m below the undercut in an offset herringbone layout. The drifts are 4.5 m x 4.2 m. The ore is coarsely fragmented and of high rock quality. The drawbells are rectangular and spaced at 34 m apart. The production footprint is 126,000 m2 (650 m long x 200 m wide). The ore is drawn evenly at an 85-degree draw angle to minimize dilution. The design column height is 460 m. There are 320 crosscuts and 20 drawpoints. Resin grouted roof bolts, cable bolts, fibrecrete, and steel sets are used as support. [2]

Equipment

The equipment used includes 20 LHDs, 4 jaw crushers, and conveyors. The 20 LHDs are manually operated and diesel powered. Each LHD has a 6.5 m3 bucket with a 12 t payload capacity. The LHDs use the Modular dispatch system. The fleet mucks from drawpoints to 4 crushers. The 4 Krupp jaw crushers are sized at 1700 mm x 2300 mm with a 750 t capacity for storage below. The crushers break the oversize to -220 mm. The 4 crushers are able to crush about 3000 LHD buckets of ore per day. The 1800 tph inclined conveyor at 9 degrees transports the ore into 2 storage bins near the production shaft. The average haul length is 175 m. [2]

Mine Access

The mine consists of 4 shafts (exploration/production, service, production, and ventilation). The service and production shafts are spaced 72 m apart. The service shaft is concrete lined, 10 m in diameter, and reaches 1,280 m below the surface. The service shaft can reach a maximum speed of 12 m/s. It has an 86 m headframe, a single deck cage with fixed guides, and an 8 person capacity cage with rope guides. The production shaft is concrete lined, 7.4 m in diameter, and reaches 1,280 m below the surface. The production shaft has a maximum capacity of 41,000 tpd. It has a 106 m concrete headframe, four 32 t skips on rope guides, and 2 automated host winders with 6000 kW motor. The raise bored ventilation shaft is 5.76 m in diameter and reaches a depth of 924 m below surface. [2]

Ventilation

The ventilation system supplies airflow of 600m3/s. The fresh air intake is at the production and service shafts and exhausted through the ventilation shaft. It consists of two 1,250 kW main exhaust fans, two 850 kW booster fans, and a 18 MW refrigeration plant used to cool the intake air. [2]
  1. Moss, A. (2011). An Introduction to Block & Panel Caving. BMO Capital Markets 2011 Global Metals & Mining Conference. Rio Tinto.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 Palabora Mining Company. (2010, March). Competent Person's Report.