Murray & Roberts Cementation has made an excellent start to the Konkola North decline sinking project, achieving a 220m advance per month in the first 14 weeks.

This was during the rainy season using one suite of equipment in adverse ground conditions, where all development ends were wire meshed to the face before the blast, and with site establishment being conducted concurrently.

Jan Nefdt, Murray & Roberts Cementation project executive responsible for mine development, describes this as "a remarkable achievement" that could possibly be a record for this type of project. Development has continued to surpass targets. By the end of August this year 1,597m had been advanced, exceeding the targeted 1,233m. This was accomplished in 22,617 man shifts and 239,771 man hours — the equivalent of 222 days — without any Lost Time Injuries (LTIs) being recorded.

The Konkola North copper project is located north of the town of Chililabombwe, adjacent to the Democratic Republic of Congo border and north of the Konkola Copper Mine (KCM). African Rainbow Minerals (ARM) and Brazilian mining company Vale is a 50/50 joint venture established by Konnoco Zambia Ltd in partnership with ZCCM-IH who holds 20% of the project. The mine is designed for a peak production of 2.5m/t of ore and 0.6m/t of waste rock per annum.

Murray & Roberts Cementation’s scope of the work covers the development phase at Konkola North, comprising a twin decline system on the East Limb and ramps to access the ore body. This involves about 2,100m of conveyor belt ramp development, 4,000m of access ramp development and 12,900m of footwall and ore drives.

The company commenced with site establishment on 24 January 2010 and the first blast in the twin declines took place on schedule on 14 March 2010. Nefdt says adverse ground conditions were immediately encountered and in response, a strict support regime was introduced including the installation of welded mesh on the hanging wall and side walls of the declines. The mesh is held in position by split sets installed on a 1m by 1m pattern and is extended to the face position after every blast. In addition, core drilling is conducted to determine ground conditions ahead of the advancing face.

Five and a half months into the contract, the conveyor declines have been developed by a total inclined distance of 736m from the box cut on surface to the 100m level. The access decline has advanced to 426m, while a further south decline has been developed a total inclined distance of 234m.

Wyllie Pearson, Murray & Roberts Cementation’s project manager responsible for the contract, says that safety is always elevated to top priority by company teams on site. Particular measures are being applied on this project to ensure safety in regard to the adverse ground conditions and the interface between men and machines in confined spaces.

"To maximise safety on this site, before sending our team up to Zambia, we enrolled all expats, including our Australian drill rig specialists, at our Bentley Park training academy near Carletonville for refresher training," Pearson says.

Additional mineral commodity

The Konkola North ore body was originally developed between 1953 and 1959 by another mining company and exploited for about two years before being closed as a result of the poor economic climate prevailing at the time. The development of the project by the Vale ARM JV adds an additional mineral commodity to ARM’s portfolio. This will also be the first time that ARM’s operational interests extend beyond South Africa. ARM sees this as a first phase development for a copper growth strategy in sub-Saharan Africa.

The Konkola North mine is a continuous ore body comprising two distinct limbs — the South and East Limbs. The ore body strikes generally in a northeast to southwest direction and dips between 15º and 77º in a southerly direction.

Access to the East Limb will be via the new East declines being sunk from surface to the 100m level. On the 100m level footwall drives will be developed on strike for the top access of the three ramp systems, to access the ore body down to 250m level, which is phase one of the project. A set of three conveyor declines with transfer silos will be developed during this phase.

In the final configuration, ore and waste handling from underground will be by means of permanent conveyors and the East Limb material will report to either the surface concentrator plant feed or waste stockpiles.

Development from the portal access is being executed using mechanised mining equipment including Sandvik twin boom drill rigs, bolter rigs for support, Sandvik 410 and 415 load haul dumpers, 40 ton Sandvik dump trucks, emulsion chargers and purpose fit utility vehicles.