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Mammoth "Metal Moles" Tunnel Deep Beneath London
Hugh Pickens writes "BBC reports that the first of eight highly specialized Tunnel Boring Machines (TBM), each weighing nearly 1,000 tonnes, is being positioned at Royal Oak in west London where it will begin its slow journey east. It will carve out a new east-west underground link that will eventually run 73 miles from Maidenhead and Heathrow in the west, to Shenfield and Abbey Wood in the east. Described as 'voracious worms nibbling their way under London,' the 150-meter long machines will operate 24 hours a day and move through the earth at a rate of about 100m per week, taking three years to build a network of tunnels beneath the city's streets. Behind a 6.2-meter cutter head is a hydraulic arm. Massive chunks of earth are fed via a narrow-gauge railway along the interior of the machine, which is itself on wheels, as the machines are monitored from a surface control room which tracks their positions using GPS. Hydraulic rams at the front keep them within millimeters of their designated routes. 'It's not so much a machine as a mobile factory,' says Roy Slocombe, adding that the machine is staffed by a 20-strong 'tunnel gang' and comes with its own kitchen and toilet. Meanwhile, critics complain that the project is a peculiarly British example of how not to get big infrastructure schemes off the ground, because almost 30 years will have elapsed from its political conception in 1989 to its current projected completion date of 2018."
It has more gaps than any other system - you have to constantly mind them.
sic transit gloria mundi
It has more gaps than any other system - you have to constantly mind them.
That's why I prefer the Moscow Metro. Because there, the gap minds you.
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You can't count the life of a project from the date someone first thought of it. By that measure, the Apollo moon landing project took at least 100 years. You should start counting from the date significant funding began, which in this case is 2010. Not bad, compared to, say, Boston's Big Dig.
They had to add the stop because the Alternate Thursday Rule, when applied in conjunction with the Left-Hand Turns Only Method, caused too many people to end up in the middle of the Thames.
I don't know the specifics of this, but from my former work in an oilfield services company, I know that oil well drilling systems can track their own position within a few inches. One example from about 30 years ago was a set of wells drilled under an estuary in the UK. The gov. allowed the drilling company a one-acre island to do all the drilling from. They drilled down about a mile, then branched off into 10 separate holes that were drilled horizontally, following an oil seam that at times was only one foot high. The longest horizontal hole was about 10 kilometers (34000+feet, 6.6+ miles) long. Here is another reference, including info on a new well system on the North Slope that extends even farther - two miles down, then over 10 km horizontally, then back down another km or two so they can use an existing oil processing facility.
Drilling systems are among the most sophisticated technological marvels going - they include seismic signalling, mass spectrometry, neutron activation analysis, nuclear magnetic resonance, gamma ray spectral analysis, and other really geeky stuff. The bit knows where it is geographically and where it is relative to the geological structures that it is following. The computers that sit 10 feet behind the actual bit meet tougher specs than military or aerospace - 1000 G shock, very high pressures (I forget the PSI), 400 degree F temperatures. Cooling is accomplished by the drilling fluid that is going past the outside of the drill string. Truly oil well technology is the perfect geekly combination of extreme "big heavy dangerous machines" plus extreme high tech.
It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
Sometimes a white trailer is the right tool for the job. I've worked with civil engineers for years, and the ones I've worked with were pretty full-on professional. If a job needs a white trailer, that's what they trot out. If the job needs a million dollar visitor centre, then that goes into the spec.
It's probably worth mentioning that there's GPS, and then there's GPS. The sort that we are used to ("In 400 metres, exit ramp, on left, to Proposed Western Freeway"*) depends entirely on trig between orbiting satellites, another more sophisticated type augments that with intertial guidance systems. If you can read the RF from the satellites, you can use the former - and that depends on a combination of antenna design and how much (generally metal) is in the way that might soak up the radio frequency energy before it gets to the box. To a point, you can make up a lot of signal strength with a higher-spec antenna.
The latter type of (what's erroneously, but conveniently called GPS), the inertial guidance system, measures and sums accelerations and gives you a vector -- sort of like summing the movements of a small mass in an enclosed box over time. These can use accelerometers and gyroscopes to add up quite small movements and tell a computer in summary that it's gone this far, in this direction, over this interval of time. If it sounds complex, you're right -- but the technology has been available since the advent of the ICBM.
The Wikipedia entry on the subject is really quite good -- http://en.wikipedia.org/wiki/Inertial_guidance_system -- worth reading (warning, there is a lure and fascination in these things, especially when you get to laser gyroscopes...)
And as much as I like my little Garman Nuvi (*yes, it really did give me that direction once) it wouldn't be the GPS of choice for locating a major piece of underground tunnelling kit.
Do not mock my vision of impractical footwear