Looking at the various tunnel portals available, wood, random stone cut stone, concrete etc. has me wondering when the various types came into use. I have a couple of concrete portals in my “junk” box and wonder what time frame they are appropriate for. I’m modeling steam, transition era or possibly a little before then and I’m trying to decide what types of portals I want to use. So when and possibly where did the various types come into use?
Concrete tunnel portals would be appropriate for your era. Cascade and Moffat tunnels have concrete portals and they were build before WWII. And how many concrete coaling towers were around back then? Heck, the Romans invented concrete - It’s been around for a while! Concrete did not become a large structure material until rebar and mixing technologies met. Look at Hoover Dam - another concrete structure built before WWII. I think you are pretty safe here.
Jim
OK, so I can use the ones I have but wonder about the other types. I’m guessing availability of materials and locale might have had a lot to do with what portals were used. For instance a logging line might very well have had timber portals just because the timber was readily available.
Wonder what governed the choices between cut stone, random stone or concrete? I’m freelancing and not strictly following a prototype so the most interesting thing would probably be to mix and match different types but I don’t want to throw a random stone portal in there if it would be totally out of place with the cut stone and concrete variety.
I also freelance. I would think that the random stone would be first, then cut stone, then block, then concrete. A random stone portal may have also been replace at some time with a later type. I also think cost a the availability of materials would play a factor, as would the type of ground around it. If the mountain was really hard rock, a tunnel portal may not have been used at all.
As for where to use them, I would use the more modern ones closer to a city and the older types farther away, with the random stone being farthest of all.
To be a little more detailed, poured in place concrete first became a useful construction method about 1900. This was when “Portland Cement”, which is virtually universal today, began to replace the “lime putty mortar” of Roman times as the prefered masonry mortar. What the Roamns did that is compared to modern concrete actually had a much higher percentage of aggerate (sand, gravel, large stone) than does modern concrete.
Portland was developed through a series of improvements in Britain and Germany throughout the 19th Century, but did not see wide spread use in North America until after 1900. As late as the teens many brick buildings were still built with the softer lime putty mortar - not with Portland.
Concrete - as we know it today, relies on the harder properties of Portland Cement. The Hoover dam is made with Portland Cement. The piers of the Brooklyn Bridge and the Thomas viaduct are stone with lime putty mortar. They cannot be repaired with Portland Cement - it would cause them to fail.
Portland Cement is the result of much higher firing temperatures, much better control of ingrediants and much finer milling of the material after firing.
Wood formed concrete tunnel portals are easily documented back to the late '20’s and early '30’s.
Sheldon
To give a specific date, I recall a photo of a poured-in-place concrete portal which had, “1913,” cast into the top of the portal arch.
Random stone was either an early (Civil War era) or remote location choice. Cut stone came later, but probably pre-dates WWI, unless built in a place where aesthetics dictated a ‘prettier’ look.
My own prototype used a lot of rough-cut (shaped but not smoothed) stone, even into the late thirties. Then, suddenly, everything suddenly became monolithic structures of poured-in-place concrete, some seeming far more massive than necessary. Of course, a lot of that is the result of tunneling through broken, faulty rock in earthquake country…
Chuck (Modeling Central Japan in September, 1964)
The concrete portal offered by Chooch has 1899 cast into it. I have wondered if this is a little too early for concrete?
Bill
Portland cement was actually invented way back in 1824. ‘Modern’ Portland cement dates from 1871, when David Saylor of Coplay, PA developed his formula. This being all near me - this area was HUGE in the cement business at one time, but only a few plants remain. Multiple railroads linked the various plants in this part of Pennsylvania, now also almost all gone.
Here’s a link with some history: http://www.rumford.com/articlemortar.html
One of the earliest poured concrete structures is one of the residence halls at my alma mater, Lehigh University. It was paid for by Andrew Carnegie in honor of his friend and associate Charles Taylor and built in 1907.
–Randy
Randy,
All true and in line with what I said. There is a difference between invention and wide spread use.
Seems to me I did date North Amercian use to about 1900. True it was invented way before that and was used regionally in Brittian, Europe and in a few places in North America much earlier. But it was far from universal or standard in North America until the early 20th century.
Even here in northern Maryland, just a few hours from Clopay, PA, and the early Portland industry, my house built in 1901 has a lime putty mortar stone foundation and two lime putty mortar brick chimmneys. But right around the corner from me, the Forest Hill Station of the Ma &Pa, built in 1914, has a Portland cement poured in place foundation and retaining wall - both still original.
And Lehigh Portland still has a big cement plant in Union Bridge, MD, originally served by the Western Maryland. Unoin Bridge is now home to the Western Maryland Railway Historical Society and their Museum.
Sheldon
This isn’t a tunnel portal, but it is concrete:
Wayne
Lehigh Portland’s plant that was near me, just a short distance from where they still maintian corporate offices, is the one I am including on my layout.
1900 seems reasonable - it takes a while until architects and engioneers are comfortable with new materials and methods unless your name is Brunel in which case you will take a brand new and largely unproven material and build a tunnel under a river with it.
–Randy
As with a lot of RR things one thing to do is to look behind the scenes.
That is “scenes” plural.
First off there is the practical question of what the tunnel portal is holding up.
It has already been said that hard rock may have no need for a tunnel portal t all - which doesn’t mean that it won’t get one. We can work all the way from there to sand, mud and clay. All materials have their own propertes and problems. Also, as Chuck pointed out, there are other geological issues such as fault zones. risk of earthquake and so on. Mining subsidence - including long after the mines have shut down - can also be a factor.
Something that very much goes with all of this issue is what, if any, retaining walls are built in the immediate area of the portal. Once into the era of concrete these walls are often made of concrete in both the same construction method and aesthetic style. (So concrete finished to look like dressed stone in the portal will be continued through retaining/wing walls)
[I notice that one practice in use for some time.has been to make a retaining wall by boring a line of adjacent holes, inserting re-bar cages and filling the lot with concrete - when this has set the ground is cleaned away from the side that will be the cut and pre-cast blocks are brought in to provide a smart looking face. In both providing for cuts in very soft material and makng fills I have also seen large walls built up of pre-cast blocks that are subsequently back-filled]
In addition to what ground is behind the portal there are questions of what materials are available. This isn’t just what is in the neghbourhood but what the RR wants to (and can) spend out on. Where capital is allocated and the RR wants to make an impression very elaborate portals can be provided.
Sometimes only the “city” end of a tunnel gets the smart portal.Also a portal can be dressed stone or just a skn of dressed ston
I think time was more of a factor…that is, once concrete came into use, railroads pretty much stopped building in stone. Concrete was just a lot easier to use.
Logging railroads would probably avoid building a tunnel if at all possible, since it was a fairly expensive proposition. Logging lines generally only served an area for a few years until the logs were gone, then moved on. That’s why geared engines were so popular with logging railroads, they didn’t need to spend money cutting and filling to make things level, since a Shay or Climax could climb a 10% grade if necessary.