The two were saved from death by the 1.3 by 1.2 m steel telehandler cage they were trapped in. The unprecedented rescue operation involved cutting through 36 m of solid stone to their cage beneath a rock fall in the 925 m level of the mine. A sophisticated, low vibration raisebore was brought in from Rosebery to cut through the rock.

With rescuers coming from the Beaconsfield mine rescue team, Tasmanian mines and from the New South Wales mine rescue and working on the operation, the crew used a combination of hand drills, or air-legs, to work their way through the rock. Chemical agents were also utilised to make the surface more brittle and easier to penetrate.

Despite working round the clock, there were several delays that threw plans into disarray. In the face of the daunting task, rescuers worked quickly to push a 90 mm wide and 12 m long plastic communication conduit through to the men. This enabled food and other amenities to be passed through. Most importantly, a digital camera was passed down which the men used to photograph their surroundings in order to help align the borer in the right position.

Due to the unprecedented nature of the situation, Tasmanian Minerals Council Chief Executive Terry Long highlighted the operation’s complexity.

“You can’t come in from above them because it would probably collapse. The only way that they could get in was from the side and if you have to go in from the side, you don’t go straight in. So they then have to come up from underneath.”

Mr Long said that rescuers had decided to come in from the bottom at the last moment because they were afraid that a side entry would dislodge more rocks.

Initially, rescuers planned to penetrate 80 cm further than first decided before beginning the final phase of digging upwards toward the men. Rescuers planned to carve out an L-shaped escape route, but the toughness of the siltstone inside the mine prevented this. It was originally believed the horizontal section of the tunnel was 1.5 m, but this estimate was later extended to 2.3 m. The vertical tunnel was estimated at 1 m or less, but was later found to be up to 2 m thick.

Yet another setback struck later on. The initial plan to enter the level tunnel through its wall was abandoned as there was too much chance of disturbing the rocks hanging above them after the rescuers saw images taken by the two. Instead, the rescuers decided to angle the raisebore’s path slightly downward and carve a tunnel quietly below the men. The borer was operated cautiously. Able to chew rock at a maximum of one metre an hour with 80 tonnes of pressure, its revolving head cut through rock at around one third of that pace while vibration monitors outside the tunnel were checked.

Further complications arose when it was discovered that the whipping action of the raisebore could destabilise and realign it.

“The header is connected to the boring machine by a series of rods,” Australian Workers Union national secretary Bill Shorten said.

“As it moves along, you get a whipping action, like a skipping rope. That can effect the stability of the header and it can sort of effect the direction.

“There have been some corrections made and the whipping action that affects the movement of the header and, so, the blokes are optimistic there will be a little better progress this morning.”

The $A6 million, 5.4 tonne CD 1000 raisebore was at the time in use at Zinifex’s Rosebery zinc mine in Western Tasmania. As it was the only raisebore in Tasmania, it was immediately dismantled and sent to Beaconsfield where it was reassembled on a concrete base.

“Overnight, eight truck loads of concrete – or 14.4 cubic metres – were delivered to the mill and sent down the mine to create an even pad for the raisebore,” said Beaconsfield Gold Mine manager Matthew Gill.

Mr Gill also added that “The raisebore will then be bolted through the pad into the rock beneath to ensure it has a stable platform.

“The positioning of the raisebore must be precise to ensure the bore hole comes out where intended.”

Normally, raisebores are used for cutting vertical ventilation shafts and ore chutes, with miners attaching the head to the drill once a pilot hole has been made through the hard rock to guide the borer. The drill is then rotated and pulled upwards, “backreaming” to the surface as it crushes the rock.

However, in the case of the Beaconsfield operation, the borer had to work in reverse and cut a horizontal hole. Furthermore, the borer had to cut through rock that was five times harder than concrete. The 100 volt borer also had to be pointed almost horizontally, forcing rescuers to make modifications, the most notable being the concrete anchor used to stabilise the borer.

The borer was chosen because it could grind away the rock to create a 1 m wide shaft for the men to crawl through without causing much disruption to the immediate environment. This is unlike drilling and blasting, which might trigger further rockfall due to shockwaves. However, given the unstable nature of the ground 925 m below the surface at Beaconsfield, this made it impossible for the use of any other machinery or technique.

Although explosives were used initially, rescuers stopped using them as they neared the trapped men. A form of tunnel boring was then used to turn the rock in front of the machine to dirt. Mr Shorten commented, “It’s less violent on its impact to the environment around so it causes less repercussions to the rock.”

In a further attempt to stabilise the rocks, the men were sent tubes of grout which they plastered onto the surrounding rock to reduce the risk of further rockfall.

Ordinarily, rock that is crushed by the borer falls downwards as the main borer is raised to make the shaft, or downwards out of the pilot hole that is drilled first. At the Beaconsfield mine, the crushed rock had to be removed by air blasting as the borer moved on a horizontal plane.

A raisebore works by first drilling a pilot hole before a cutting disc is attached to the head of the tool, which is then pulled backwards towards the machine. But in the Beaconsfield situation the raisebore had to work in reverse because cutting equipment can only be put on the head of the tool while it is on the side of the rescuers. However, before any drilling could begin, a concrete pad needed to be built in order to stabilise the machine. Anchorage was necessary to reduce vibration as vibration was expected to increase as the tunnel progressed to target length.

The Beaconsfield gold mine is centred on the old Tasmania reef mine 40 km northwest of Launceston, Tasmania and it is the only mine in Tasmania not to have a decline access. It is also the highest yielding Tasmanian gold mine. In response to speculation surrounding its closure, Mr Long said that the Beaconsfield mine was likely to close for good because it ‘only had a year left in it anyway.’ The mine will shut down in the meantime in order to reassess its safety and determine the reasons behind the disaster.