Building a 2-track tunnel outside?

[dburrous]

Can anyone direct me to a resource regarding how to construct a mountain with a tunnel in my garden railway?  I open to suggestions:  cinderblocks? Black plastic culvert?  There seems to be lots of resources for interior tunnels, but I need one for out doors in Colorado.

Thanks for any help you can give me.

Regards,

David

ps:  Interesting that Tunnel is not listed under the "Select Tags" category.

[cacole]

We have a short 2-track, curved tunnel on our club's outdoor layout that was made of concrete.  The thing you should take into consideration most of all is vertical and horizontal clearances.  Measure your widest and tallest model and then add at least one inch more clearance on both sides and the top.

[ttrigg]

I want to echo CACOLE's remarks about vertical & horizontal clearance.

I too have a two track curved tunnel, a 90 degree tunnel. I had the luxury of working out all the possible scenarios on the concrete patio before going to the dirt of the garden. I used cinder blocks with a 3ft x 3ft concrete paving stone as cap stones. Beginning with the known track radii I was working with, I moved cinder blocks around until I achieved 2 inches clearance between cars in opposing direction and 3 inches clearance to the tunnel walls.I took this design and went to the dirt. First layer of cinder block went on a cement footer half a block deep in the dirt. The outside wall was square corner so I was able to do the standard half block offset for strength. The inside wall was to be "curved" so I did a simple straight vertical stack. Re-bar in a 'horseshoe bend' used to secure each vertical stack to the next. Re-bar also crosses from interior to exterior walls, which makes for a nice footing for the 3x3 paving stone roof. I covered this all with 2 layers of roofing felt and one layer of the rubber membrane used in the Koi pond. Then i built every thing up with river rock and fractured flagstone. I then added another layer of rubber membrane to waterproof everything. My tunnel not only turns 90 degrees but also passes under a waterfall for the Koi pond. 

[Jerry Barnes]

There is some photos of the in process construction of my tunnel on my web page. Click on the projects button, I think.

[dburrous]

Hi Jerry:

Thanks for your link.  I'll take a look at it.

I appreciate your help.

Regards,

David