Has any RR or the TTC out in Colorado tried laying rails directly onto cement? No ties, no rock roadbed. Just rails secured with clips laid onto cement poured in sections.
I think there are some installations like that in a few long tunnels. A combination of difficult work space for replacing ties and foundations about as stable as you can get seem to be the reasons for it IIRC.
I think that even when laid in cement there are sleepers or ties to hold the gauge in most instances.
That is an awful lot of weight that has to be supported, and pavement has to be maintained and occasionally replaced. Look at interstate highways and airport runways. It is a lot easier to refurbish roadbed and replace ties than it is to tear up and replace pavement.
Concrete alone cannot support the weight or vibration of a train. Even trolley car tracks had crossties buried under the pavement to hold the rail in place.
I have seen some old photos of streetcar tracks being installed that used steel plate ties to hold the rail. It was difficult to see close up detail of these steel plate ties to determine if the rail was welded to them or held in place with bolts. And what was done to prevent these ties from rusting out?
There is a grade crossing on M50 just east of Charlotte MI that appears to have large concrete slabs instead of ties.
Ye gods, can you people not read?
Slab Track for the Next 100 Years - AREMA
Concrete Slab Track Test on the High Tonnage Loop at … - AREMA
or to put the systems in a wider context
And in case someone starts to bring in transit track practice,
H-Fuller-APTA-AREMA-Differences
Both systems tested at TTCI have been around for dog years, and are thoroughly evaluated.
Variants of mud jacking work well for line and surface where shims are inexpedient. Of course, if you want extremely-high-speed alignment, l
Concrete grade crossings are slabs to support automobiles; The rails are still supported in the conventional manner.
Dave is right. The ‘better’ crossings have the slabs made modular, with reinforcement including ‘hardpoints’ for lifting, so that track maintenance can be easily achieved without demolition.
For years, I accepted the idea that resting the crossing slab edges directly on the ties was changing the track modulus, and that was a reason for the increased wear on the approach rails about 150’ to either side. One of the FRA tech reports seemed to indicate this was hooey… same with ‘track tuning’ for bridge approaches and the like to give smooth transitions between track sections with different effective moduli. I am tempted to mutter “E pur si muove” – but can a couple of mudchickens with experience mention what the truth is?
I had thought a lit of underground rapid transit was steel rail on concrete. IIRC the rail is mounted on rubber pads. Also San Francisco’s cable car operation is all rail on concrete. Again on rubber pads. As I remember it when they do track work(rarely) they have to jack hammer in to get to the track. The installation was designed to put the money in up front
Continued(pushed the wrong button) The current structure was designed to out as much money as possible on the front end to make the system last another century or so. As the city was not projecting any expansion of the current system it was easy just to set the whole system in concrete. Rgds IGN
First of all I’ll be a nitpicker and comment about “Cement.” Cement is incorrect terminology because cement can be anything from Portland cement to Duco’s cement sold decades ago in Woolworth’s. Probably what you mean is concrete, which is a mixtire of cement, sand, and rocks, In any case, semantics and nitpicking aside, I saw my first slab track in Italy on the line north out of Gorizia and running into Austria several years ago. I’d never seen it before but obviously it’ had been in service for a while. I understand that it is being tested for service in the US. I have no clue whether it would stand up to the axle loadings of US trains, but seems to hold up well enough on the lighter Euro loadings.
(Wait till somebody discovers what asphaltic concrete is)
With slab track, you had better have very stable, consolidated subgrade or the whole thing fails.
Paul is correct on the TTCI statement, but there were other locations outside the FAST track that failed miserably . (the failures do not lie around long at FAST, unless you know where to look)
Bolting rail to slab concrete and expecting it to survive is a bozo no-no. The concrete slabs in play these days have suitable protection to protect against going into tension.
Crossing slab track and pac-track are a mixed bag. (ATSF had a massive failure on the Eldorado Line Change that was subgrade induced that destroyed 3 miles of slab track in 1978 - the whole length of that line change’s fill section slopes has some really peculiar looking rip-rap. )
EDIT: Sorry, no caffeine in system during original post.[:$]
I’m not a fan of the stuff for heavy haul applications or crossings (fixed structure w/ plenty of impact beating by overweight and borderline illegal combination vehicles)
“(Wait till somebody discovers what asphaltic concrete is)”
The lay public tends to refer to any asphaltic pavement as “Tar” and any concrete service as “Cement”, at least around here in the Northeast US.
I note that the word “Tarmac”; British English for Asphaltic concrete pavement (it’s short for “Tar Macadam”) has entered US usage but only in referring to the paved surfaces at Airports (be they concrete or asphalt).
And of course, a crew laying hot- mixed Asphalt paving material utilizes a piece of equipment still known to many as a “Steam roller”…
THE EARLY PILE RAILWAYS.
Engineering News—October 6, 1892
Travelers over the western end of the Erie, and over the Lake Shore road in northern Ohio and eastern Michigan, must have often noticed long double rows of piles, occasionally running through shallow cuts, and evidently intended for some form of railway. They are an evidence of one of the earliest delusions of American railway construction, provoked by a dearth of labor and superabundance of timber, that a railway perched throughout on piles would have the best possible roadbed at least cost.
The key to understanding this is to separate the wild financial gyrations from the engineering. The ‘respected engineer’ sentence should imho have gotten better attention.
If you want a graded roadbed in minimum time, you do it with piles. Since there were no expedient sources of concrete, or equipment to make arches or other supports, wood was used, and clever automatic machinery (who has an earlier example of an automated tracklaying machine?) was used for the “finish grading” cutting off. Note the seven-foot gauge. I don’t see much about ‘best possible roadbed’ but I can think of a WHOLE lot worse subgrade methods for a job that size to be completed in that timeframe. We might also recognize this was less than a decade after Stevens’ ‘temporary track’ became a replacement for frickin’ stone blocks anchoring the rail spans.
For the ‘long run’ you’d fill in ballast around and between the piles as you had the money, just as you would for a trestle replacement. With revenue from operating trains coming in, there would be funds for actual subgrade and ballasting to get a ‘permanent way’ with the
Research in Norway indicates that continuously supported rail has less wear, less noise, and less vibration than steel on ties or pads. Modern light rail systems in Norway use slab track with continuous artificial rubber between the steel and the reinforced concret, with resiliant attachments like Pandroil clips or equal. New Orleans Canal Street line is similar and survived Katrina without damage.
Contact me at daveklepper@yahoo.com for the Norwegen reference. Not in my head at the moment.
I know there are different mixes of concrete and it would be reinforced of course but in construction we have a saying, it’s not a matter of if concrete will crack but when. To me that seems to be the issue, maintenance would be expensive.
The platform tracks at Chicago Union Station were rebuilt in the 1990’s to rails directly mounted on concrete. The process was rather involved and the track gauge was laid out in advance for positioning the anchor points before the concrete was poured. It replaced an arrangement similar to that found in subways of rails resting on half-ties set in concrete.
I think that solution (pilings) was workable for those areas due to soil conditions. Some of those swamps (NW Ohio in particular) would have required copious amounts of stone to provide a stable sub-roadbed. Driving piles to a set refusal might have been faster/cheaper in those situations to achieve a stable roadbed.