# Tunnels: How do you do them?



## East Broad Top (Dec 29, 2007)

Consider this a survey for tunnel-building techniques. I'll be writing about that in an upcoming series in GR, and I'd love to showcase examples of the materials other folks have used for tunnels on their railroads. Also, if you've got examples of what _didn't_ work, and what you'd do differently, I'd love to hear those stories as well.

Thanks!

Later,

K


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## SD90WLMT (Feb 16, 2010)

Can't say what doesn't work......

I simply use basic cement building block..in sizes as required....
I do this for one reason...to control compressibility....meaning whatever is placed over the top will not get closer to a train as time passes....requiring a tunnel rebuild..

Block is spaced 8" - 10" for internal clearances widthwise ... a cement cap is placed over the top of the two walls to close it off....

Dry stack works here...I usually add cement tho to prevent movement...and stop the caps from displacing also....

A barrier placed over this structure..such as a large HD trash bag...placed to lay over the top ..drapping over the sides also helps keep a tunnel dry from ground moisture.
The only other consideration might be drainage inside...so water does not pool internally..

This is also strong enough to follow with what ever one may want for scenery..or even a path for walking over...with some creativity...

You might also consider a paragraph on sizes of tunnel openings for internal clearances....each scale requires a different size...

I have seen other layouts built that ran say a 1/32 or 1/29 train just fine, but with the current popularity of 1/20.3 in greater use...and growing loco sizes...these would hit the smoke stack upon entering the same tunnel...planning ahead is important..our outdoor hobby has changed and grown over the years.... (this follows the other one large problem people say - "I wish I had built with larger curves" ).

Good luck K.

Dirk - DMS Ry.


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## East Broad Top (Dec 29, 2007)

Thanks, Dirk. I know exactly what you mean with the tight clearances. All of the tunnels on my dad's line were built to 1:22.5 clearances. He's rebuilt most of them with taller, wider clearances, but two currently remain original. They've been responsible for more than a few broken smokestacks. 

Later,

K


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## Paul Burch (Jan 2, 2008)

I do it with 12" plastic drain pipe. I have a form to pour concrete portals. Sand is used under the pipe so it is easy to set final grade. Before setting the pipe I drill some holes on the bottom side to allow for drainage. The track is attached to Trex or similiar material and slipped into place. And yes if you really want to look inside a tunnel you can see the round pipe, but in practice you don't notice it. The pipe I use is the black corregated stuff,not the rigid green pipe.


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## docwatsonva (Jan 2, 2008)

I built my tunnel using stepping stone pavers and concrete bricks. After I dug the trench, I put down stone dust and leveled and compacted it. I next laid down the 16" sq. stepping stones and filled the gaps with concrete.










Next I glued down 1 layer of bricks, on their sides, and then glued 2 more levels of bricks, on end. All bricks were glued using concrete, weather-proof glue.










I lucked out and a friendly tile guy cut my stepping stones at angles to make a snug fit for the roof. I don't have a picture of that step. I finally covered the roof with several layers of plastic and packed stone around the base to hold down the plastic and provide some drainage. The height is sufficient to handle 1:20 shay and Connie stacks. I don't run my k27 through it because of the curve radius.











Here's what it looks like today after 6 years.










Doc


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## Mike Gibson (Feb 8, 2013)

I'm in the middle of constructing my tunnel for my new layout. It's on a 12.5 foot diameter curve. I decided to go with concrete construction. Since I was matching the tunnel to the curve of the track, and that I'm an engineer and have access to CAD and a plotter, I printed a 1:1 plot of the tunnel floor to use as a template for my wood forms. I constructed a frame to hold the shape until I had it staked in the ground.



























Once I had the floor poured it was back to my template to frame the forms for the walls. I sandwiched foam inserts in the ends that will form the tunnel ports.



























I'm hoping to pour the walls on Monday weather permitting. After that's is done and I remove the forms on the inside, I will cap the top opening with tile and the pour a cement roof on top of that to finish it off.


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## toddalin (Jan 4, 2008)

For a "straight shot," a piece of 10"-diameter PVC is hard to beat for ease and strength, especially when it is free scrap.


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## NTCGRR (Jan 2, 2008)




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## Greg Elmassian (Jan 3, 2008)

At the risk of offending my buddy Dirk, don't use plastic trash bags to deflect moisture, they are designed to decompose!

Greg


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## Homo Habilis (Jul 29, 2011)

Make certain that you can reach inside to address any derailment or track type issues.

Consider the various unwanted critters that may find the tunnel a perfect place to set up housekeeping.

It's the usual "don't ask me how I know". Suffice it to say this has a bit to do with my decision to build indoors.


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## SD90WLMT (Feb 16, 2010)

Greg...in how much moisture does this occur?

I got "none" here....but plastic is OK too...

Now....that part about offending...wha....!!

Dirk


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## catherine yronwode (Oct 9, 2013)

I have two tunnels. 

One is curved and it is made of concrete blocks with a rocked-in "planter box" built on top to stabilize the top of a fairly steep hillside. A small tree is in the box, along with a lot of draping plants that cover the rockwork. Because this tunnel is curved, you can only see a short way into it from either end.

The second tunnel, which was built earlier, was made from a PVC drain pipe and i hated it from Day One. Even blind as i am, i could see the corrugated plastic drain pipe innards. That got fixed by Daniel Smith who scumbled the inside with mortar to look like a squared-up area instead of a round tube, and and to look like rough rock instead of plastic. He then sprayed it matte black inside. Now it looks great. 

He then finished the innards of the first tunnel the same way, although with far less mortar, just a hand-coating for roughness. He sprayed that matte black inside, and i was happy. 

cat
ET&WNC
East Tennessee and Western Northern California RR
"The Two-Tunnel Line Through the Mountains"


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## East Broad Top (Dec 29, 2007)

Thanks, guys! I may be hitting y'all up for higher resolution photos if you have them at some point down the line.

Doc, what's the glue you're using? I've ended up using similar bricks on mine (two courses of cinder blocks was too tall), and I'm thinking that while dry stacking may be sufficient for my application, it wouldn't hurt to show how to use proper adhesive. 

Later,

K


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## docwatsonva (Jan 2, 2008)

Kevin,

I used PL Polyurethane Premium Construction Adhesive. It's water and weatherproof. Got it at Lowes.

I used it to build my retaining wall 3 1/2' high 6 years ago and the glue hasn't shown any signs of deterioration.










Doc


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## White Deer RR (May 15, 2009)

I have one four foot tunnel, and I just built it out of left over PT 2 x 4's from a fence project, and attached the ubiquitous Aristo foam portals. These portals have to be centered just so or the stove pipe on my Sierra cars will catch it. With floating track I occasionally find the track has wandered enough to cause a problem.

Someday I want to build timber portals, hopefully I will have leftovers from a current project. Visitors seem to like the look of the faux stone, though, so who knows...

I did use a couple of black trash bags on the tunnel, not knowing that was a mistake. I did caulk all the wood joints with outdoor silicon, so it will probably be okay for my purposes. Worst case I have to move a little dirt, a few plants and get some actual outdoor use black plastic.


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## Pete Thornton (Jan 2, 2008)

My tunnel was a 6' straight shot through 2 pieces of chimney liner, which must have been 3' long and about 9" ID. (It went away in 2003, so forgive me if my memory has faded.) It was under a tree that dropped crud on my track, and the constant dropping covered the tunnel very quickly. The ends had stone portals made from odd bits of flat garden stone.

The floor of the tunnel was covered by a piece of wood - probably a 1x8 - suitably weathered so it looked like floor. The sides had strips of wood to hold the track in place in the center. A 6' long strip of track floated on the wood, and could easily be removed if necessary, but it never was. 
Only once did something hit the side - a big Accucraft 1:20.3 (Fn3) caboose with marker lights sticking out the side. The track was adjusted back into the exact center and it squeeked through.

Cleaning was easy - a pad on a broom handle was pushed through to get rid of all the leaves that had accumulated.

It worked well until the layout was dismantled. You can just see the north portal in the top LH corner of my sig block (I found the original scans of the prints from 2001 if you want me to post it.)


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