In message
-sept
ember.org, at 21:46:40 on Sat, 25 Mar 2017, Recliner
remarked:

One limiting factor on tunnel size is that they have to bear the weight of
575 tonne A380s a few metres above.

You've not seen the highway tunnels with their portals only metres away
from the runways at Schiphol? https://goo.gl/maps/K5NbbmjqqL42
--
Roland Perry