A giant drill, called the Robbins Tunnel Borer, broke through nearly two miles (3 kms) of rock and softer ground on Wednesday (10 May) to complete the major stage of a tunnel under Zambia's Chingola Copper Mines in the country's Copper Balt.
A giant drill, called the Robbins Tunnel Borer, broke through nearly two miles (3 kms) of rock and softer ground on Wednesday (10 May) to complete the major stage of a tunnel under Zambia's Chingola Copper Mines in the country's Copper Balt. The tunnel was needed to divert the Nchanga stream in order to enlarge the mine's open pit -- already one of the world's largest. The stream currently flows over the path of the new ore sits.
The American-made Robbins borer weighs in the neighbourhood of 110 tons. One of the largest in the world, the machine was brought to Zambia and assembled specifically for the job. It's designed to go through the particularly hard granites that lies along the route of the tunnel.
The machine cuts a path 12 feet (3.7 metres) in diameter and the project has taken over a year to complete. Drilling operations were delayed because of cave-ins amidst softer ground along the tunnel's path.
During the operation, guide hole had been drilled to enable engineers to bring the machine out at the correct place, and a laser beam was used to ensure perfection. At the end of its two-mile path, the drill was only inches (centimetres) out of lins.
The tunnel will convey water from an open pit and discharge it into a large open-cut channel. This channel will finally link up with the existing path of the Nchanga stream to complete the diversion.
At its deepest point, the tunnel is about 250 feet (76 metres) under Nchanga north township.
When the drilling operation was finally completed, engineers and mine workers cheered as the crew of the drill followed it through the newly-made hole. Then the workers and the crew posed for photographs.
The mine at Chingola is managed by the Anglo-American Corporation, Central Africa, who own 49 per cent. The Zambian Government owns the remaining 51 per cent.
SYNOPSIS: Chingola, in Zembia's Copper Belt, is the site of one of the country's major mining centres. And there, for over one year, a big project to divert the Nchanga tream has been under way. Engineers went to enlarge the mine's open pit, which is already one of the world's largest. But the stream runs over ore sites. So they decided to move the stream. And to do it, they dug a two-mile tunnel to give the water an underground path. They used a massive drill called a Robbina Tunnel Borer for the operation. On Wednesday, the crew of the drill finally broke through to the other side. The drill had been brought from the United States and assembled in Zambia just for this job. Technicians used guide holes drilled in the rock to make certain that the machine came out at the right place. Perfection was ensured by laser beams.
At the end of the job, the drill was only inches out of line. The tunnel borer grinds a hole 12 feet in diameter through the rock. One of the world's biggest, the one used in Chingola was designed specially for the hard granite that lay along the two-mile underground route. A number of mines and pressmen were on hand on Wednesday to watch as the drill broke through the final few remaining feet of rock.
Mine workers showed their satisfaction as the first member of the tunnel borer's crew clambered through the hold in the wake of the machine.
When completed, the tunnel will convey water from an open pit and discharge it into a channel. This channel will link up with the present path of the stream to complete the diversion. At its deepest point, the tunnel cuts 250 feet below Nchanga north township. Although the job isn't over, the men were able to relax.