Burly tunnel workers cheered, clapped and clinked glasses on Friday as the tonnes of rock under the Swiss Alps crumbled away to open a path for the world's longest tunnel.

"For miners and tunnel engineers this is the greatest moment in their life, the breakthrough," explained Hans Ehrbar, chief construction officer for the Alptransit tunnel company.

But the emotion reached its apogee in the village of Sedrun when miners from north and south crossed through the gap made by the mammoth drilling machine and a wooden icon of Saint Barbara, patron saint of miners, was passed to colleagues on the other side.

"Saint Barbara, look it's Saint Barbara," miner Roberto Guerreiro pointed, as he watched the underground ceremony on big screens along with several hundred colleagues at the mid-way tunnelling plant and access nearly 1,000 metres (3,000 feet) above.

"We work for an objective, so when you see it reached..." the Portuguese tunnel worker told AFP, struggling for words and touching his heart with knowing, briefly tearful glance.

"I have already worked in two other tunnels. This is the best, the longest," he smiled, in reference to the record-breaking 57-kilometre (35-mile) Gotthard base tunnel.

Guerreiro has given his life for the new tunnel over the past six years, leaving his wife behind for ten days at a stretch in the central Swiss city of Lucerne 95 kilometres away while he kept company with explosives.

For Guerreiro was on the northern side, which was mainly cleared through blasting and digging, spending eight to nine hours underground in humid conditions at temperatures of up to 50 degrees Celsius (120 Fahrenheit).

"This is work I love," said Guerreiro, insisting that safety precautions were unrelenting.

The tunnellers faced a big rock collapse during construction, crumbling earth, unexpected subsidence and sudden blasts of piping hot geothermal water escaping from the rock.

Before the breakthrough, the tunnel was blessed by a Roman Catholic Bishop and a minutes silence was held for eight workers who died during more than decade of construction work, nonetheless a far cry from 200 who died more than a century ago building the old Gotthard.

Asked about the Chilean miners rescued this week after 69 days trapped underground, few dared to tempt fate by mentioning their ordeal.

"I think they did an excellent job in Chile," Ehrbar told AFP, preferring to highlight the rescue.

Shrines to Saint Barbara stand at each tunnel access, carefully tended by the hugely devout tunnelling fraternity from Austria, Germany, Italy, Switzerland and other European countries and even, early in the project, from Lesotho and South Africa.

"Day by day they dug into the depths of the Gotthard to places where no human had been before," Luzi Gruber, a senior executive at one of the constuctions companies, Implenia, told journalists.

At the tunnel face, Swiss Transport Minister Moritz Leuenberger admitted that words were not enough to thank the miners.