Word for a single tunnel within a "tunnel complex" or the complex itself

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:

gov.uk

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.

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

For example,

panynj.gov

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...

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.

M-W:

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..