Large Scale Central

My Long Tunnel has FAILED !

Track and Trestles
#1

Well it was a good run of 10 years but the roof of “pinch point” tunnel has failed and trains are not allowed to enter it. The tunnel was constructed using cement blocks and a gravel floor around 5’ diameter track that was staked into the ground and a track power line was attached to it. The tunnel is nearly 15’ long which required 3 hatches to be installed. The roof of the tunnel was an odd shaped horseshoe so I used 2 sheets of plywood that were sandwiched together for strength, painted and then wrapped in plastic. As we all know water will eventually find a way in and that has caused the plywood to rot. The WYE on top came at a later date and the leg over the removable girder bridge leads to the main yard.

As you can see replacing this tunnel is going to be a big job but it has to get done. My plan is to take up the plywood, remove the cement blocks for reuse and instead of reusing the 5’ track that has created a problem on the RR, hence the “pinch point tunnel” moniker, I will use a 6.5’ curve. I would really like to squeeze a 8’ diameter curve in there but I don’t have the room. To the side of the girder bridge is a deck. I will rebuild the tunnel using the cement blocks and then I will cement the floor. The gravel that was in there seemed like a good idea at the time but over the years different critters have gotten in to dig around causing derailments.

My big question is what to use for the new roof? I’m thinking about cement board and cutting holes in it then use plastic trim wood that is glued to it to create the “chimneys” for the access hatches.

Today I have longer equipment like the DoodleBigger and my 250 ton crane that has a long overhang that rubs on the walls of the tunnel so I will also plan for that but how strong is cement board meaning how much of it can be unsupported and still allow 200 pounds to stand on it?

What do you think? How would you approach this project? Thanks.

#2

To walk on it, I think I’d use cement pavers covered with gravel.

#3

I’d call in Devon and let him think on it! (https://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)

#4

Todd,

I used 18" square cement stepping stones for the tunnel top and bottom and stacked cement bricks for sides. I had someone cut the top stones to fit on my curve. He used a diamond tile saw.

(http://largescalecentral.com/FileSharing/user_2849/Misc/Tunnel-2.jpg)

Doc

#5

That is nice clean work Don. How did you manage a hatch?

#6

No hatch Todd. It’s only about 7 ft long. I guess you could make the center stone removeable somehow.

Doc

#7

Todd, for your tunnel I would do like Don did, and if you wanted extra strength do 2 side by side courses of bricks alternating them to add more walk on strength one row like this === the next row like this llll then the top of the pavers with a removable hatch every arm length or so, and a paver or cement bottom like you said.

#8

I basically did a combination of what Don and Pete have suggested but using slightly different materials. That is a piece of cementicious board under the bricks to keep dirt and rock from finding its way onto the track. A second piece is underneath to prevent critters from burrowing up or weeds from growing down. It extends under the bricks so they do not shift or sink during frost heave.

#9

I just did a similar tunnel to Don’s and Todd’s. I did the paver walls, glued together, then covered with a slurry stucco coat inside and out, built around a double 8’ curved track (well really an outer 8" and then a alternating 5’, 8’ track piece to get about ~7’ curve), sandwiched them as tight as I could, but alas could not get under the magical 18" paver size (that was the goal to use those). I then looked at cement pipes, casting my own roof, etc., but settled on plywood. I might have went to the extreme though on it…

3/4 inch marine grade plywood, cut into 3 curved shapes to cover my tunnel

2 coats of exterior house paint

about every 1.5 to 2 feet, drilled through the wood and used Simpson metal straps on top/bottom to provide strength over the center of the tunnel

anchored through the wood with concrete screws into the brick walls so it would not shift. Also with liquid nails (brick to wood bond) and silicone around all nail heads and seams.

Foil HVAC tape over all screws, seams, etc.

Finally the 40Mil bathtub liner applied with liquid nails to the top/sides of the wood, covered with dirt and flowers for final product.

Its been about a year and all still looks good, even after the tons of rain we got in CA this winter. No sagging or warping as of yet when I look through the tunnel and I was, a heafty 200+ lbs walking around on top of the plywood prior to backfill, plus now with about 6 inches of dirt and flowers above it too no problems. Hoping to get 10+ years out of it like Todd did :slight_smile:

-Chris

#10

Don Watson said:

No hatch Todd. It’s only about 7 ft long. I guess you could make the center stone removeable somehow.

Doc

Yes Doc , or the pavers removable where the structures above reside . Drill through the pavers and make a 12x12 or 16x16 paver lift up with hidden rod and bolts through them .

Only my thoughts from the pictures posted by Todd

#11

if the old tunnel lasted ten years, just use the same method, you had used then.

that is about as long, as a house goes between renovations, or longer than most cars serve…

or take plastic drainage pipes, cut lengthwise and put upon the walls, then covered with chain-link fence material and pour concrete upon it.

that would make for a fine bomb shelter for your trains.

#12

I decided to dig in (pun intended) and get this project started. I removed the track and made notes on the wiring of the WYE and got to digging. The plywood was in worse shape than I thought it was being totally rotted out.

The good news is that I think I can use half of the old tunnel. I put some of the new 6.5’ track in there and placed my crane on it with the boom overhang and it did not hit the side wall. Now comes the hard part of knocking out the blocks that I have to move and then putting it all back together.

#13

Todd

You can cut the pavers with this blade installed into a normal skill type saw. Image result for masonry blade for circular saw

When cutting were a mask ( dusty ) I just lay the paver on a dirt base and just cut…

As for your hatch , look in the sprinkler/plumbing section of Home Crapo for this …

#14

Todd, I used ground contact 4X6s sitting on top on landscaping blocks walls, similar to the blocks that you used for your tunnel approach walls, but inside the tunnel. Then I covered the lumber with rubber pond liner scraps to stop percolating water. If you installed the lengths of lumber perpendicular to your “U” shaped roadbed it looks like you may not have to worry about cutting any angles to match the curve. On the bend use long pieces putting them straight across the curve. Just another idea. It worked great for my three tunnels, one of which is covered by about 2" of fill. Mark

#15

Todd,

In my 50 years in construction one of the most important lessons I learned was Wood Should Never come in contact with soil for long term survival. Pressure treated ground contact wood has a short lifespan compared to concrete. Even Hardy backer Board will rot in ground contact. Don Watson’s use of concrete stepping stone is a bullet proof method. Your block walls look to be in good condition, really, all you need is to top it off with concrete stepping stones. They’re easy to cut with a diamond saw. Good to see your track change helped solve the clearance problem, good luck with your project.

#16

Dan DeVoto said:

Todd,

Don Watson’s use of concrete stepping stone is a bullet proof method. Your block walls look to be in good condition, really, all you need is to top it off with concrete stepping stones.

Pretty much

#17

UPDATE! The Hole is a Whole Lot Bigger! The good news is I will be able to use half of the tunnel so will only have to rebuild the other half. Lining the tracks up I will be moving the top side and gaining another pass through siding but a trestle will need to be moved and a wall rebuilt. On the other side the main will be moved about 18" over into the yard which will mean moving the pony truss bridge over and moving a 6’ long tunnel but it is exciting and will be really cool.

The wye switch that is sitting on the bucket is the approximate location it will be going. The lift out bridge section that goes to the Right of it will need to be remade from 48" long to 36" long but the tunnel comes first.

The next step is to start putting the tunnel wall blocks back up.