Mean Machines: Tunnellers, Friday March 3

mean machines: tunnellers (5/10) 19.30–20.00

Many of the most essential construction projects rely on tunnelling machines. As the latest edition of Mean Machines graphically illustrates, these subterranean rock-munchers come in a wide variety of shapes and sizes.

First up is the world’s largest tunneller, the Wirth TBE-500. At 180 metres long and weighing 1,000 tonnes, this is a truly gargantuan Mean Machine. As it uses its six arms to cut a pair of motorway tunnels through a mountain near Zurich, the TBE removes a staggering 400 cubic metres of rock every hour. By the time it reaches the other side, 1,200,000 cubic metres of rock will have been ground into rubble by the TBE’s hardened-steel cutting heads. In some cases, it’s too difficult and expensive to bring these leviathans back to the surface – one of the machines used to dig the Channel Tunnel was steered into a tunnel of its own, which was then collapsed around it, sealing the machine in a grave of its own creation.

In Finland, a far smaller but no less exciting machine uses the power of liquid explosive to create a tunnel through hard rock. Called the Rocket Boomer, this bizarre spider of a machine uses four independently moveable arms to drill up to 140 six-metre-deep holes in the rock face. The holes, which are precisely mapped using a computer, are then filled with liquid explosive. The charges detonate at five-millisecond intervals in a spiral pattern, sending 1,000 tonnes of rock flying in all directions. When the dust clears and the rubble is removed, a neatly-cut section of tunnel is revealed, and the drilling begins again.

Sometimes the tunnellers require a more subtle solution to that provided by the Rocket Boomer, and that’s where the micro-tunnellers come in. One such machine is demonstrated working beneath a row of houses in England. Steered using a laser guidance system, the unmanned five-metre-long tunneller slowly creates a space beneath the foundations, while sections of pipe are forced through immediately behind, reinforcing its work.

In Switzerland, a slightly larger machine known as the Vertical Incline Shaft Tunnel Boring Machine specialises in working uphill. Using hydraulic brake pads to brace itself against the tunnel walls, this machine climbs slowly through the inside of the mountain to a reservoir. Its tunnel will help to provide the power for a hydro-electric power plant. It makes sense to tunnel upwards because this allows the rubble to flow easily down the tunnel, rather than having to be removed piecemeal by other machines. This spoil, referred to as ‘muck’, can then be used in other construction projects.

It is beneath the town of Lausanne, also in Switzerland, where the ultimate tunnelling Mean Machine is to be found. The Road Header is a caterpillar-tracked vehicle that varies in weight from 40 to 150 tonnes, and which sports an extendable arm at the front. The arm has a spiked metal fist at its tip, made from specially treated steel, which spins at high speed. This formidable appendage can carve out 30 square metres of rock without having to move the vehicle, allowing the Road Header to create a tunnel of any shape. The only problem created by this machine is dust – as the huge cutting head comes into contact with the rock wall ahead, the rock is turned into a fine spray which must be sucked away by powerful fans before it damages the eyes and lungs of those working in the tunnel. At £1.3 million, the Road Header may not be the cheapest vehicle on the market, but it is certainly one of the most impressive.

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  • Angus SPEIRS

    The programme was really exciting with its display of machines. Working as I am in the tunnel industry, the footage filmed of these machines was impressive. Where/how can I get a copy of this programme?

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