In December 2000, the Bellambi West longwall mine in New South Wales is bolting up the longwall face prior to moving out of the current workings under the Cataract Dam.
Under Bellambi West’s original mine plan, longwall operations were due to continue under the Cataract Dam till 2003, followed by the relocation of the longwall to the western reserves. However, the relocation to the western reserves has been brought forward after an in-seam drilling program, carried out by Valley Longwall Drilling in March 2000, identified a 35m fault. The fault was 800m closer to the operating longwall face than previously thought and essentially made further mining in the Cataract area uneconomical.
While longwall reserves in the Cataract area have been lost – up to 3Mt – pillar extraction in this area has already begun and will continue operating for about four years at a planned rate of 700,000 ROM tonnes per year. To ensure contractual obligations are met, a second pillar extraction unit will start operations in January 2001 with both pillar units operating six days per week.
Although only a fraction of the remaining Cataract coal reserves will be recovered eventually, the good news is that it was not the longwall which found the fault, but management caution and foresight.
To man the pillar operations, mine manager John Milner said experienced operators had been recruited from the closed Avon, Oakdale and Brimstone operations to supplement the existing workforce. So far the pillar operations have been going really well he said, with shifts already nearing targeted production rates.
By the 2001 second quarter, longwall mining is expected to restart in the western area on a fully developed block left when the mine was sold to Allied. Roadways have since deteriorated and development crews are currently cutting through floor heave of up to 2m in places. No further secondary movement is expected to occur. Before longwall operations can resume, development will focus on reclaiming these old mains roadways.
In the Cataract area of the mine, longwall mining was constrained by the proximity of the dam wall which affected pillar design and block dimensions. The move to the western area, which is not subject to these constraints, will also allow Allied to change several operating parameters which improve the opportunity to optimise longwall mining.
Regular gateroad chain pillar dimensions will be reintroduced and a reduction in development burden of over 60% realised. Longwall panels in the western area average in excess of 1Mt compared with about 400,000t in the Cataract area.
“The combined effect of a significant reduction in development burden and a 250% increase in longwall block tonneage assist the operation appreciably and more than offset the forecast minor reduction in yield,” said Allied managing director Steve Baldwin. “Total yield is forecast to decrease from 80% to 78% with fractional splits changing from the current 62% coking and 18% thermal to 54% coking and 24% thermal.”
The block dimensions in the western area will also be adjusted. In the Cataract area the previous owner was extracting blocks at 110m wide, subsequently increased to 150m by Allied. In the western area blocks will be further increased to 200m wide with a first block length of 800m. No new equipment will be needed to support the increased width. However, base lift will be fitted to the longwall face to allow the face to work through an area of soft floor in the first two longwall panels in the west.
The coal preparation plant will also be upgraded to increase capacity to 3Mtpa, improve efficiency and lower operating costs, scheduled for completion before longwall extraction begins in the western reserves.
“The two most significant achievements at Bellambi West in recent times have been safety and development unit performance,” Baldwin said. “The Bellambi West underground operation is now one of the safest underground mines in the country having operated for over 13 months without a lost time injury. Given the turbulent times the industry has been facing this is a remarkable achievement.”
Lying ahead for the Bellambi West mine is a future with over 22Mt of recoverable Bulli seam reserves in front of the longwall.
Bellambi West is unusual among Australian longwall mines in that it is both owned and operated by contracting group Allied Coal. Apart from a handful of operations, such as Queensland’s North Goonyella, operated and part-owned by Thiess, most other longwall mines are owner-operated. This subject is covered in greater detail in an interview with Allied Coal managing director Steve Baldwin, due to be published on ILN on December 18.