# tunnel building material



## ewaldbee (Jan 5, 2009)

I need to build a 6 foot long straight tunnel through heavy clay. Is it best to use concrete block or that 10 inch plastic culvert product from Home Depot. Are there better options?
Thanks, Ewald


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## denray (Jan 5, 2008)

think about this is water leakage going to be a problem? If so how do you deal with that. 
The culvert will turn water better, but the blocks will drain better out the bottom.
Dennis


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## Garratt (Sep 15, 2012)

Whatever you do, making the tunnel with some fall towards the ends will keep water from stagnating. Ballast can be used to make up any difference.

Andrew


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## Dan Pierce (Jan 2, 2008)

I used 12 inch serrated aluminum for my tunnel. When adding ballast and track I lost an inch in diameter plus I have only 10 inches really for overall rolling stock clearance.
I am able to run 1/20.3 through this tunnel.


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## riderdan (Jan 2, 2014)

ewaldbee said:


> I need to build a 6 foot long straight tunnel through heavy clay. Is it best to use concrete block or that 10 inch plastic culvert product from Home Depot. Are there better options?
> Thanks, Ewald


I'm in the process of building a mountain with a tunnel through it on my layout. From my research, 10 inches isn't going to be near large enough.12" would be more reasonable. Keep in mind how much ballast you need to put in to "flatten" the floor and how wide you need it to be. The chord formed by the floor line needs to be wide enough to clear the ties on the track plus any overhang your locos and rolling stock. Plus, the distance between the chord and the top of the tunnel needs to be higher that your tallest loco.

Another thing to think about is drilling holes in the bottom of the tunnel material (if you're using corragated culvert or pipe) for drainage. This would especially be true if you're using corrugated, since the corrugations are going to prevent water from running out of the tunnel. I plan to put down a 5" deep bed of gravel under the culvert to improve the ability to drain water out. Of course, if you think the pipe is fairly safe from serious water flow from the ends, the corrugations will also help keep water out unless it gets deeper than them.

I do think that plastic culvert is a good option. But in a larger size. It's already black, so you don't have to paint the inside. It's completely watertight (until you drill holes in the bottom  ) and likely to stay that way permanently, unlike something built out of concrete blocks. Also, it's flexible so as Dan mentioned you can put the ends lower to help with drainage. If your tunnel is likely to get really flooded, drainage holes might not be sufficient--having then ends lower would make a big difference.


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## Pete Thornton (Jan 2, 2008)

I used 9" clay chimney liner. It comes in various sizes and lengths at your local HD or Lowes. Very strong. The track was laid on a 6' piece of wood that I could remove if it needed fixing. The track floated on the wood [wasn't tied down] but thin strips along each side prevented it moving too close to the wall. I pushed a broom with a pad on the end through the tunnel before sending a train through.

Straight tunnels are much easier to deal with than curved ones!


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## John J (Dec 29, 2007)

Don't forget to take into consideration The Tallest piece of rolling stock you are going to run. All my tunnels are around 12 inches tall. 

JJ


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## Paul Burch (Jan 2, 2008)

If you have clay that won't drain I would build in some drainage under the tunnel. Four inch perforated pipe in small rock should work to take any water out. I like 12" solid pvc for my tunnel linings. I will usually drill some random holes in the bottom so it can drain. In this case it would drain into the 4 inch pipe below it. I live in a wet climate so I'm very conscious of drainage.


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## dieseldude (Apr 21, 2009)

Here's an option for you-

http://largescalecentral.com/forums/topic/22149/iron-island-rr-take-two?page=6


-Kevin.


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## Paul Burch (Jan 2, 2008)

That does illustrate what I was suggesting for drainage under the tunnel.


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## ewaldbee (Jan 5, 2009)

dieseldude said:


> Here's an option for you-
> 
> http://largescalecentral.com/forums/topic/22149/iron-island-rr-take-two?page=6
> 
> ...


Thanks for the link. Looks like a good option and well thought out. I do get concerned about these Minnesota winters and the frost heaves that might affect moving those blocks around.

Ewald


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## cephius (Jan 10, 2008)

Ewald, where in Minnesota are you?

Dave Acevedo - Rochester, MN


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## ewaldbee (Jan 5, 2009)

cephius said:


> Ewald, where in Minnesota are you?
> 
> Dave Acevedo - Rochester, MN


Chisago City---about 30 miles north of St. Paul


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## David Leech (Dec 9, 2008)

Someone that I know built a long tunnel, it must have been 10 or 12 feet, and used a large diameter green coloured pipe.
He then covered it with a LOT of dirt.
It worked fine for a while, but after a couple of years a train got stuck in the tunnel!
He found that the weight of the dirt on top had actually flattened the middle part of the tunnel.
All the best,
David Leech, Delta, Canada


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