Tunnel portals.

Try Scenic Express. They have quite a few options, some of which look like concrete or you can finish them to look like it. 

I use precision board, See how to work with Precision Board Garden Railways Aug 2007, you can cut, shape and score it to look like any thing you want. Its a lot of fun to work with. If you have a sign shop near by see if they use it and maybe they will give or sell you their scraps. here are some photos of some of my Precision Board projects. The bank, under pass, Baby Ruth Building, Oil Tank, Church, Brick Wall, Tunnel entrance and Santa's Sleigh are all created from the Precision Board

Wow Gene, That sure is some great work! I never heard of precision board. I'll have to study up on that!

I used Celotex to make my tunnel portal.  Stacked up like a layer cake, held together with glue and nails pushed through the layers like rebar in concrete.  Painted earth color with cheap latex paint.

Paint on white glue and cover with sand.  The portal painted charcoal grey to represent concrete.

Steve

Could you make a rubber mold of the one you built and run them off in plaster. There you could do some final shaping with the plaster model?

Precision Board http://precisionboard.com/ seems like great stuff. Thanks for introducing us to it.

You'll like them better painted

I would have added a strip to the horizontal and gone a little fatter on the pillars if you want to get picky, but paint is what they lack.

These are HO but the same idea works for any scale. Construction is plywood with a thin coat of plaster sanded smooth to cover the grain. I patterned them from actual SP concrete tunnel portals built 1910-1920's. I made these wider than scale to accommodate trains on curves. It's a good basic design that looks authentic.

Last photo is tunnel 21 near Oakridge Oregon. I've seen other versions with vertical wing walls, which are somewhat easier to build.

where can I buy  Percision  board   What kinds of stores. I tried signs stores and no one had any 

You have to find sign shops that make wood or 3 dimensional signs, sign shops that just make paper signs won't use it. I f you find a shop that uses it I'm sure you can get their scraps. Also try Rainbow Ridge Kits, 9030 Palomino Ridge Dr. Lakeside CA, 619-561-0643...

Coastal Enterprises Co., PO Box 4875, Orange CA 92863, 800-845-0745 - 714-771-4969

Good Luck

l

My first one looked horrible. So I tried again and I'm happy with the way it came out. What do you guys think.