These road schemes with tunnels, how far underground?

[saaby93]

When you look at road schemes like stonehenge or hindhead where they build a tunnel just to get the road out of the way under ground, how far underground is it?
It must be a few metres to the roof of the tunnel and the tunnel is what 10 metres high - so the road is say 15 metres under ground?
Or much deeper?

[vonhosen]

Rather depends on what elevation the road starts/finishes at & the summit height it passes under. Mont Blanc tunnel is 2480m below the summit it passes under, making it IIRC the second deepest in the world. Deepest being the Gotthard rail tunnel.

[saaby93]

vonhosen said:

Rather depends on what elevation the road starts/finishes at & the summit height it passes under. Mont Blanc tunnel is 2480m below the summit it passes under, making it IIRC the second deepest in the world. Deepest being the Gotthard rail tunnel.

I was interested in the minimum that's normally required for these projects

[vonhosen]

Cut & Cover tunnels aren't going to be very deep at all. A lot of the London tube tunnels are only 5-6m below the surface.
The Heathrow airside tunnel is a bored tunnel & the roof of that in the middle is about 7 or 8m below the surface because it has to snake over the top of the Heathrow express rail tunnel with about 2m separation between the tunnels at that point.

[irocfan]

IIRC Crossrail have managed to thread one of their tunnels over one of the deep tube lines and under one of the not-deep tube lines, with not a whole bunch of space in either plane

[saaby93]

What about where they go under housing?
What sort of gap do they leave to make sure theyre not in the cellar?