Not sure how they should positioned, should the portal be in the hill or the out side of the hill?
Few pictures where I am now.
Cuda Ken
Ken,
Here you are…Google your eyes out!
http://images.google.com/images?gbv=2&hl=en&q=railroad+tunnel+portals
Don Z.
In my experience, portals are cut into the face of the hill. The only exceptions I have seen were located in slide-prone earthquake country, including one where the bare tunnel lining extended about 25-30 feet from the face of the hill, with a regular tunnel portal at the end but no wing walls.
Chuck (modeling Central Japan in September, 1964)
Feather River Canyon (UP, was WP).
Mark
Where and how tunnel portals are installed depends on the earth material the tunnel is going through.
If rock, they would be on the face.
If rocky ground, they would probably be set back in the hill some, with short concrete wings and some light retaining walls to help keep the rocky ground in place.
If in soil type country, they would be farther back in the hill with substantial wings and retraining walls to keep the ground form collapsing on to the track.
Portals at the club
Solid granite, portal flush to cut
Portal extended, shelf for rubble and loose soils
Thanks for the link and the Pic’s.
Ken