Narrabri finishes third drift

WHITEHAVEN Coal’s Narrabri operation has completed the third drift at its Narrabri coal operation as it prepares for longwall mining in the new year, general manager Greig Duncan told the Longwall 2010 conference.

Lou Caruana

The mine, which sits in the Gunnedah Basin of northern New South Wales, will then be assessed for suitability as a top coal caving operation, he said.

“We have three drifts that are interconnected that go down to access the coal seam and pit bottom area,” he said.

“Each of the drifts are 1100 metres and go down in a one in eight grade.

“Two drifts were completed in June this and the third drift was completed in October.

“As the third drift went down it encountered a mix of shales and sandstones, we then come into a dolerite sill, which was quite hard so we reverted from a roadheader operation to a drill and blast operation through the sill, and once we exited the sill we then reverted to a roadheader operation until we reached the conglomerate.

“The conglomerate sits just above the coal seam itself in the east. We then had to decommission the roadheaders and commence drill and blast through the conglomerate until we accessed the coal seam.”

Duncan said the mine will begin mining using longwall mining methods with the ability to retrofit top coal caving.

“Initially it was going to a bord and pillar operation, with a three-year gap for when the development goes in – but the aim now is to concertina all that and go straight to a longwall operation,” he said.

Pre-draining techniques are only required for the majority of the northern blocks and no drainage in the southern side.

Narrabri’s Bucyrus longwall will have a 300m face, an operating range of 2.8-4.5m, two-legged shields, except at the tail gate where they will be four-legged, and shield widths of 2m.

The capacity of the run of face supports is slightly under 1400 tonnes and the three tailgate supports are slightly over 1800t capacity support, which was necessary to maintain the minimum 110t per square metre support level.

The mine will have an EL 3000 shearer with 2100 kilowatts of power.

“One feature of the shearer is the 200 kilowatt long plate on the tailgate side which was necessary because of the hardness of the coal,” Duncan said.

The AFC has got a nameplate capacity of 3500t.

“One of the key features of the design is that it has got to allow a retrofit for top coal caving during a face change with the necessary equipment if it becomes necessary,” he said.

“Part of the studies we have to undertake on top coal caving is how the coal breaks up in the goaf and how it supports the rear of the supports.

“We can do all the studies we like but until we do that first panel we do not know how that coal is going to behave.

“The intention is to complete the studies by the end of the first panel.

“The earliest top coal caving equipment could be delivered is longwall 3 because there is seven months delivery for the equipment package to retrofit.”