WI/PC UNDERGROUND UK MOTORWAY NETWORK BUILT USING 200ft WIDE TBM's

WILDGEESE

Gone Fishin'
With the UK's under developed and crowded motorway network plus all the trouble with upgrading roads up to motorway specs, and building new motorway regarding the Green & NIMBY lobbies, how doable would it be to put new and existing motorways underground?

What I envisage is a TBM with a bore width of 200ft allowing a motorway to be dug with 6 lanes (10ft) each either side of a 10ft refuge plus a 25ft hard shoulder for safety plus slip ways at junctions up to ground level traffic.

Could this be done?

Could a TBM be built with this bore width?

Would it be efficient enough to use in regards to energy use?

Would ventilation be an issue with exhaust fumes?

Regards filers
 

gaijin

Banned
Think about this for a second: what is cheaper and easier to do, updating a road network above ground or completely starting a new network with the added cost of putting it underground?? The answer is not that difficult.
 
With the UK's under developed and crowded motorway network plus all the trouble with upgrading roads up to motorway specs, and building new motorway regarding the Green & NIMBY lobbies, how doable would it be to put new and existing motorways underground?
Long story short: probably technically feasible, barely. Might be cheaper to just bury the existing roads to create the tunnels and move the ground level up a few hundred feet.

What I envisage is a TBM with a bore width of 200ft allowing a motorway to be dug with 6 lanes (10ft) each either side of a 10ft refuge plus a 25ft hard shoulder for safety plus slip ways at junctions up to ground level traffic.
Playing along, why not stack two or three decks to fit 10 traffic lanes into a substantially smaller diameter tunnel like this? It'd save a lot of digging. At the very least, use the leftover space for trains or expansion of the national electric grid or something.
 
Or, taking on board the situation, build motorways on bridges above the existing railways which would bring motorways directly into city centres.
 
Something similar was studied - briefly - for London:
http://www.cbrd.co.uk/articles/underways/

The suggestion was to mine 60-foot diameter tunnels, containing two three-lane carriageways, a monorail, and pedestrian walkways (!) under London. Along with underground interchanges between nine such motorways, and underground car parks.

When the Ministry of Transport was finished with the idea, their analysis was that the idea "will not in fact repay further study or effort either generally or in its application to London". If you can't sell deep motorway tunnels in London, you can't sell them anywhere.
 
The widest bores used today, for large-diameter road and rail tunnels, are about 50'. For roads a single bore gives you 4 lanes in each direction if you're willing to compromise on lane width, or 3 if you're not; for trains, a single 40' bore gives you two levels each fitting a track and a station platform, and the main saving over small-diameter twin bores is that you don't need to blast caverns for stations. Not even the world-class experts in setting money on fire that are Amtrak and the FRA will propose 200' bores.
 
They'd get filled up zombies eventually, obviously...

Seriously I would think:

In country areas, if there is a demand to widen the motorway, you just use existing farm land next to the motorway.

In suburban areas, I imagine they would just dig a trench where the existing road is, build a road in the trench, and roof it over another road.

Urban areas are the only areas where bored tunnels is likely to make sense, but I can't see it happening in parts of central London, because of all the tube lines, and government tunnels in the central London area.
 
For comparison

http://tunneltalk.com/images/articl...r-soft-ground-bored-tunnel-review-Image-1.jpg

a small handful of these cost less than $100M/mile, but others range up past 4 times that.

100 miles of motorway at $100M/mile is 10B$, which is a lot.

And that's 50ft (+/-) tunnels, not 200.


I think economic feasibility would begin to be approached in e.g. London, where you can't just dig up the entire city.


Note that Boston's Big Dig (3.5 miles) ended up costing some 15B$
 

hammo1j

Donor
What about a right wing government using prisoners or the unemployed to dig the tunnels by hand?
 
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