REDUCING COAL DAMAGE AND LOSS WITH A NEW BLASTING TECHNOLOGY

摘要

For many years Ramp 24 at Ensham mine in Queensland, Australia has suffered substantial coal loss and damage due to the fragile nature of the coal and problematic geological conditions, which have proved very challenging. In the past various blasting techniques were applied in attempts to improve coal recovery. One approach was to use a shallow throw (cast) blast followed by a separate post-strip blast underneath. Another method was the introduction of the practice known as "baby decking" with the addition of a large buffer of material in front of the coal. However, despite increasing mining costs, none of these techniques adequately reduced coal edge loss and damage.This paper describes how the new mining technology of Stratablast™ has been implemented at Ensham Mine to improve coal recovery and productivity. This technology employs electronic initiation systems and complex modelling to combine what were traditionally separate blast events, such as a throw blast and a stand-up blast, into a single blast event. Several layers are drilled, loaded and fired in one cycle, with a unique blast design assigned to each layer. Within each layer the blasts have different powder factors, inter-hole delays and directions of initiation. Additionally, delays of several seconds may be used between the various layers.This technology has been used routinely in Ramp 24 at Ensham since August 2005. Several aspects of the process have been highlighted during implementation, namely; the vital importance of explosives column location, managing issues associated with the presence of large amounts of water, dealing with varying geology and ensuring blast implementation exactly followed design. All these aspects had to be well understood and rigorously controlled; on occasions when this control was inadequate some coal damage did occur.The introduction of this technology has seen coal recovery levels increase dramatically along with providing good productivity without increasing the number of drill and blast cycles.