10 Questions You Should to Know about Tunnell Lliner

Just like for ponds, there are many different types of materials that get used to make tunnels watertight. Everything from inexpensive dampproofing materials that are meant to keep MOST of the water out, all the way up to full waterproof membranes that are designed to keep ALL water out of the tunnel. Depending on what's inside the tunnel will determine how much waterproofing protection will be desired. For example, for a pedestrian walkway under a road, it would likely be best to prevent water from entering the tunnel and dripping on pedestrians. However, if a little water did get through, it's not a mission critical failure. In contrast, if the tunnel contained some expensive electronics or other equipment that MUST remain dry at all costs, then it becomes much more important to choose a tunnel liner that is 100% waterproof.

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One of the biggest misconceptions we hear from people looking for a tunnel liner is they might not need a liner because they&#;re using high quality concrete that is supposed to be waterproof. While it&#;s true that PERFECT concrete should be fairly waterproof, in our experience, we&#;ve never seen concrete that doesn&#;t crack over time, even if it&#;s just a tiny bit. Water loves imperfections in concrete and will find and seep through even the smallest cracks. Another place for water transmission is concrete pour joints, which are the seams between an already hardened concrete section, and a new pour of concrete. An example of a pour joint would be the floor to wall transition. If you ever walk through an underground parking structure, you will often see moisture coming out of the floor to wall concrete pour joint for this very reason.

One of the main factors that will determine what kind of tunnel liner will be best is the location of the tunnel. Is the tunnel above ground or below ground? What kinds of water sources need to be protected against? For example, for an above ground tunnel that may go under a road, or another application where the tunnel is going &#;through&#; something rather than &#;below&#; something, you may only have to deal with rainwater that seeps through from above. However, if there is a &#;green roof&#; or other types of irrigated vegetation above the tunnel, then perhaps a more robust waterproofing system might be required to prevent irrigation water from entering the tunnel. Similarly, if a tunnel is below ground, then groundwater may become an issue. Depending on the location, If the tunnel is deep enough, the structure may actually end up below the water table. This means that the tunnel will be subjected to very wet conditions most, if not all, of the time. If the structure is far enough down, hydrostatic conditions might become apparent, which means that water is being forced at the structure under pressure. In these situations, a very robust waterproofing system is required to prevent leaks. A tunnel under hydrostatic pressure could be likened to it being built through a lake or pond, where the pressure of the water is pushing down on the tunnel, trying to force it&#;s way through every crack or weakness in the structure.

Although there are a few options out there for liners, our favorite tunnel liner option is Premium RPE, which stands for reinforced polyethylene. It is strong, lightweight and can be MADE IN A SINGLE PIECE in any dimensions you like up to about 60,000 square feet. That means that if you have a tunnel that is 50 feet long and a 10 foot diameter, we could make a single piece of RPE liner to wrap the tunnel from end to end. All the seaming will done by us at our facility and as such , there is no welding or assembly on site required. This is in contrast to something like PVC, which is often sold in rolls, and then heat welded together on site. This requires full crews of skilled workers, which can increase the cost of the liner tremendously. Although RPE is commonly used as a lake or pond liner, it is also used in many different industrial applications to either contain water, or keep water out of a structure like a tunnel. We have millions of square feet of RPE in use in North America..

If you have a tunnel liner application you&#;d like to hear our recommendations on, please contact us. We provide free design assistance with no obligation to buy.

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Got yet another one for the forums. Earlier today, I was working with Hydrocal for the first time in quite a while. I was trying to build a tunnel liner using the Woodland Scenics Tunnel Liner mold. In the process I ended up with a bunch of problems. First, when I tried to put the Hydrocal in the mold, it ran all over the place creating quite the mess. (Most of it was on an unfinished plywood floor, so that wasn&#;t a problem.) In that process, I was unable to get the back (top surface) of the mold completely level. After I managed to get it reasonably level, I let it sit for the 40 minute cure time. When I tried to clean the excess off, I found that even after letting the casting cure even more, that the material was not anywhere near what I would have expected for hardness. As a result, I ended up throwing the entire casting onto the trash pile.

My questions are these: Did I do something wrong with the mixing that caused the Hydrocal not to work? Should I have waited longer before putting everything in the mold? Was I not patient enough before I tried to remove the casting? Is there anything else that I need to know about the liners?

As usual, any assistance the forums can provide will be most welcomed.

I would say it was too thin. I&#;ve used that process a lot starting off using Plaster of Paris to make tunnel walls and that worked good but Hydrocal works better. That being said if you mix either too thin it is super runny. I mix my batches thick almost like a molding mud that you can work with your hands. Hydrocal sets up quickly when mixed thick so you can&#;t dally.

Edit:

I use touchy-feely method for demolding my castings. Both Hydrocal and Plaster of Paris heats up as it cures when it starts cooling down it&#;s ready to remove.

If you have a lot of tunnel sections to make be very careful with the WS plastic mold as it will crack easily. Work the mold off starting at the long end.

I&#;ve really never followed the manufacturers directions, as a kid in the 40s my Mother made Plaster of Paris figurines and I was the pre teen &#;mixer&#;. We would spend hours filling molds with me mixing so it&#;s a natural thing for me.

I don&#;t use a ratio, I add water to the powder until it becomes thin enough to poor, like an old fashion thick milkshake. One important thing is do not become a tight wad and try to salvage leftover plaster or Hydrocal, once it&#;s mixed and it has started to setup disturbing the ratio by adding either water or powder screws it up!!! If you need more toss the old and do a restart.

As Mike said for added strength imbed some coarse fabric to the outside of the casting. I&#;ve been using a 2&#; wide medical wrap from the local pharmacy, the stuff they use making casts. You can use a spray bottle of water to wet the plaster and use the gauze strip as joiner tape. Mix a soupy batch in a bowl and dip the material in it and apply to the wetted plaster casting like making a broken bone cast.

Was the casting crumbly after it hardened? How old is your Hydrocal, and how have you had it stored?

I got down near the bottom of a big container of Hydrocal one time and had that problem. I think the Hydrocal had absorbed water in its years in the jar, and once that happened it just wasn&#;t going to work anymore. New Hydrocal, no problem.

I sometimes make curved castings by bending a flat casting around a form after the Hydrocal has set up for about 8-10 minutes. I use clear plastic wrap over the back face of the casting. In your case, you might try pouring the Hydrocal and gently rocking the mold back and forth while it sets up.

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It&#;s a bit off-topic, but this is how I did the interior walls in my subway system:

I bought a large sheet of styrene and cut it into strips. Then, I mixed a thin slurry of Hydrocal and applied it with a paint roller. This is basically how textured ceilings are done. I let it set and sprayed it first with gray primer and then with just a mist of black. At that point, the styrene strips held the Hydrocal but they were still flexible enough to bend them and attach them to the foam walls of the tunnels.

Sounds like maybe your Hyrdocal is old, so may not be a formula issue. However, if I was going to modify the formula for this specific app, I&#;d go with either 1.5 plaster to .5 water OR 1.25 plaster to .4 water. Basically bump it 10% to 20% toward a drier mixture.

One way to do this is to simply measure the standard amounts, then only pour part of the water in, adding it little by little until you get just enough to get it wet or a little more. It won&#;t be as strong as it could be, but you don&#;t need a lot of strength here, just get it to stay in the mold until it dries.

Bob,

Good idea! Gotta love how Sculptamold is so versatile. The advantage it has over the WS molds is that it&#;s very customizable, especially with curved tunnels&#;

But you could actually use the WS mold and fill it with Sculptamold, too. It&#;s going to be much easier to fill and cast with the mold and it holds detail darn near as well as Hydrocal. Plus it won&#;t break anywhere near so easily and will be lighter than a version cast with plaster of any kind.

That is an interesting idea. I was eventually going to have to get some Sculptamold for my hills anyway, so that might be a good way to kill two birds with one stone as it were. (As I have a lot of Hydrocal portals and retaining walls on my hills anyway, keeping stuff light is a very good idea. And those hills aren&#;t exactly small either. One of them is roughly 5 feet tall by 2-2.5 feet wide and the other is 2 x 2-2.5 feet. Built from beadboard stryofoam.)

Am I correct in presuming that one would use a putty knife or something similar to put the Sculptamold into the liner mold? As I remember Sculptamold is fairly thick when it is mixed. (It has been awhile since I used that item as well.)

One of the great things about Sculptamold is that you can vary the moisture content accordling to need. It&#;s much less sensitive to that than plaster, where you can&#;t get too far off from the specfification or things start going wrong.

I&#;d take a suitable amount and add water and mix until it&#;s evenly wet and works easily so you can push it into the mold. A yogurt cup or similar size container woulld allow you to mix a batch right in it. A good stiff-bladed putty knife is ideal for mixing and applying it.

I actually have a couple of MIcro-Mark flexible rubber bowls that I used today to make a couple of batches of the Sculptamold. (Something that I had hiding in my old bedroom at the ranch where I grew up. My Mom found them when she was cleaning and, of course, had no idea what they were! But that&#;s another story entirely.)

With a little bit of practice, the Sculptamold was quite easy to work with. In the process, thought, I have run into a slight problem: I ended up with air bubble remnants in the castings. (The four that I have can be used in hidden areas as the tunnels aren&#;t daylighted all the way throught.) I presume that I didn&#;t vibrate the forms enough.

What would be the best idea for solving that problem in the future? The best idea that I can come up with would be one of the cheap 3-legged vibrators that a certain box store carries. If there are any other ideas, please let me know.

That sounds about right. You don&#;t want it soupy or even a slurry. But you want to work up the flavor or binder stuff so it&#;s nice and wet to fill those bubble spaces instead of air.

I mounted my mold to a piece of wood IIRC. Tapping it could help, I was just thinking that the secret is in the sauce on this more than technique. Don&#;t be afraid to add more water right at the beginning if not mixing wet enough for you. Same with throwing in some more Sculptamold if too wet. Unlike with plaster, this won&#;t hurt if you&#;re still mixing and haven&#;t stopped stirring yet, so to speak.

I tried the idea of my 2:3 mix on Saturday while waiting for family plans to come together. Unfortunately, for some reason that mix ended up way too wet. The castings ended up too thin and even after 24 hours (approx.) the castings hadn&#;t cured. They broke apart when I tried to unmold them. I also discovered that even with that mix the castings ended up having air buble remnants. I ended up using the pieces which were still flexible (Play-Dough consistency) and plugged some scenery holes with it.

I then tried a 1:1.25 mix. While that mix still had a few bubble remnants, it cured fairly quickly and I was able to unmold them easily. I think I will run with that mix as it molds nicely and it also is nice to work with when I&#;m covering hills.

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