I would like to differentiate between a tunnel (i.e. the Channel Tunnel) and one of its 'sub'-tunnels. For example the Channel Tunnel is a 'tunnel complex' consisting of three 'sub'-tunnels - one service tunnel and two main tunnels. So, either a word for the complex (other than the name) or a word for a 'sub'-tunnel would do.

For instance, in Dutch there is the word 'tunnel' to describe the tunnel including all 'sub'-tunnels and the word 'tunnelbuis' to describe a single 'sub'-tunnel. 'Tunnelbuis' can literally be translated to 'tunneltube' or 'tunnelpipe'.

In the Wikipedia article of the Channel Tunnel there is mention of three 'bores'. However, this does not seem to be in widespread use or specifically for a tunnel created with a TBM.

Example sentence:

The southern _____ of the tunnel is 30cm longer than the northern _____.

4 Answers 4


Civil engineers talk of a bore.

The southern bore of the tunnel is 30cm longer than the northern bore.

In that sentence, tunnel could gain a capital letter because it stands for the name of the tunnel: Channel Tunnel, Dartford Tunnel, Mont Blanc Tunnel.

I haven't yet found a dictionary entry which specifies that bore can be used for a tunnel. However, it's not just engineers who use the technical term, nor is it necessary to capitalise the word tunnel. The following quotes are intended for consumption by the general public. My emphases here:


To enable traffic to continue to be able to travel in both directions over the crossing only one bore of the tunnel will be open to northbound traffic during the overnight work. When work takes place southbound, the Queen Elizabeth II Bridge will be closed and southbound traffic will be diverted to use the eastern bore of the tunnel.

The bores have separate height restrictions and overheight vehicles will be diverted via the M25.

Kent Messenger, a local newspaper

The west bore of the Dartford Tunnel was closed after a crash involving a car and lorry crashed on the M25 anticlockwise this evening.

The accident closed both lanes on the northbound approach with traffic is being diverted via the east bore.

  • 2
    As a Chartered Civil Engineer (although my expertise is bridges rather than tunnels): "bore" is only applicable if the tunnel is bored, i.e. created by a tunnel boring machine (TBM, as noted in the question). For a cut-and-cover or immersed tube tunnel, using "bore" would be incorrect. That said, where it is a bored tunnel, "bore" is definitely the right word to use when you want to avoid using "tunnel".
    – AndyT
    Nov 30, 2016 at 15:42
  • @AndyT, out of curiosity, what would be the correct terms for the other tunnel types?
    – user812786
    Nov 30, 2016 at 17:48
  • @whrrgarbl - If I had a decent answer for that, I'd have posted it! I think I'd just use "tunnel" and expect the context to make it clear whether I was just talking about one part or the whole complex.
    – AndyT
    Dec 1, 2016 at 11:58
  • 1
    Most cut-and-cover tunnels are constructed as a single tunnel, even if there is a dividing support wall, eg A1(M) Hatfield Tunnel, so it becomes context-specific. That tunnel has an eastbound carriageway and a westbound carriageway, and I can't think of a better way to identify those individual parts of the whole -- but my civil engineering degree course is now a very long time ago!
    – Andrew Leach
    Dec 1, 2016 at 12:33

In the US one often uses tube to refer to one of the tunnels in a set.

For example,


The New Jersey-bound north tube is closed. Customers advised to access the Lincoln Tunnel via the center tube using entrances at 36th Street and 9th Avenue...

  • Another example: "More than 3,000 people visited the Caldecott Tunnel on Saturday and Sunday to help celebrate the structure's 60th birthday and tour its concrete warrens. [...] The original tunnel consisted of two concrete-arch tubes. A third, tile-lined, bore was added in 1964 to accommodate increased traffic from Contra Costa. "
    – njuffa
    Nov 30, 2016 at 16:57
  • But don't use that in England. People will think you mean "underground railway network", which includes tunnels, track, stations and trains.
    – Scott
    Dec 1, 2016 at 3:14

At the risk of sounding overly punny, I propose channel to represent a sub-tunnel, and tunnel (itself) to represent a tunnel-complex purely on technical grounds (based on presence in a dictionary in the suitable sense and not necessarily as tunneling jargon).

The southern channel of the tunnel is 30cm longer than the northern one.


channel noun
2 a : a usually tubular enclosed passage

tunnel noun
2 a : a covered passageway; specifically : a horizontal passageway through or under an obstruction


I'm no English major, but as a software dev I'd say array to refer to them all..

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