Since numerous international conventtions define "Z" as the axis of spindle rotation then it looks like there won't be a "Z" as their is no spindle. Why do you need to indulge such fantasies? The roadway is well defined now. Your Cartesian sytem won't even tell you whether or not it is on railway property.
tdmidget If you arer trying to apply the cartesian coordinate system used in machine tools to rail roadway then it cannot be done.
Why not? (Apply x-y-z Cartesian axes to civil structure, that is...)
WGS-84 and the ephemeris algorithm alone disprove that stupidity. But three axes for 3D track structure (which PDN's discussion of slab-end displacement clearly concerns) are also perfectly admissible, whether we define z as vertical or use some other standard for reference plane.
What would you suggest be used for the axis orthogonal to the x-y plane for 3D structure?
Paul_D_North_Jr Volker Landwehr said (above): "To avoid misalignment at joints dowels or tongue and groove constructions can be used." Those methods address only the deflection/ displacement (i.e., in the Y and Z directions) at the joint, and not the slopes or angles approaching and leaving the joint. That only guarantees that at any dip at a joint, both sides will be equally far down. Such a loss of support is not good for the ride on the rail above, depending on the depth and length. I'd still like to know what the average and maximum 'normal' axle loads are used for the design and actual operation of such slab-track systems, as well as the speeds. - PDN.
Volker Landwehr said (above): "To avoid misalignment at joints dowels or tongue and groove constructions can be used."
Those methods address only the deflection/ displacement (i.e., in the Y and Z directions) at the joint, and not the slopes or angles approaching and leaving the joint. That only guarantees that at any dip at a joint, both sides will be equally far down. Such a loss of support is not good for the ride on the rail above, depending on the depth and length.
I'd still like to know what the average and maximum 'normal' axle loads are used for the design and actual operation of such slab-track systems, as well as the speeds.
- PDN.
What do yopu mean by "Z" and "Y" directions? If you arer trying to apply the cartesian coordinate system used in machine tools to rail roadway then it cannot be done.
BaltACDSaw a clip on Facebook about how to cook water!
One of the Home Ec classes when I was in Jr High managed to burn water (or rather, they melted the pan...)
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Norm48327 BaltACD Only after eating my late MIL's cooking. She could ruin boiling water.
BaltACD
Only after eating my late MIL's cooking. She could ruin boiling water.
Saw a clip on Facebook about how to cook water!
Never too old to have a happy childhood!
BaltACDTums
Norm
Norm48327Tons vs Tonnes. Long tons; Short tons. Just plain old tuns. Life can get confusing. Welcome to the English language.
Tums
Tons vs Tonnes. Long tons; Short tons. Just plain old tuns. Life can get confusing. Welcome to the English language.
Paul, I had a mistake in some axle loads. I found Boegl's German language broschore today and both version show metric tons. Here are the correct axle loads:
For Europe 27.5 tons, ICE-train 20 tons, Chinese high speed train 19 tons. For heavy freight traffic 46 tons at 68 mph are possible.Regards, Volker
RMEThere is an interesting discussion on the conversion of a 100mph line which needed rebuilding due to what I understood as being subgrade instability -- the specific details on how the subgrade was remediated here would be highly interesting.
I have looked into their German language broschure of their China projects. The soft soil in place was improved with all kind of piles, mostly CFG-piles with 24'' geo-grid reinforced cushion. I think that won't help to improve soil with track in place.www.bbri.be/index.cfm?dtype=services&doc=tc17_Ground_improvement_in_China_by_Zheng.pdf&lang=en
To improve existing rail lines jet grouting may be useful:http://www.kellerholding.com/soilfrac-compensation-grouting.htmhttp://www.kellerholding.com/soilcrete-jet-grouting.html
Perhaps vibro compacting or vibro replacement may be possible depending on soil type, non-cohesive or conhesive.Regards, Volker
Volker -
Thanks for your comprehensive and informative response.
For comparison, US freight car and locomotive axle loads are routinely from 33 to 36 tons, and occasionally 39.4 tons (263,000 lbs. gross weight per car to 286,000 lbs, and 315,000 lbs. respectively) on close axle spacings. Speeds vary, but 40 to 70 MPH are typical for the upper end of the speed range.
Paul_D_North_JrVolker Landwehr said (above): "To avoid misalignment at joints dowels or tongue and groove constructions can be used."
This comment was directed ar the concrete highway problems.
Paul_D_North_JrThose methods address only the deflection/ displacement (i.e., in the Y and Z directions) at the joint, and not the slopes or angles approaching and leaving the joint.
As already said, Boegl addresses this topic. Thr rail seats are about 13'' from the joint. The rail will compensate for some of this angles.
Paul_D_North_JrI'd still like to know what the average and maximum 'normal' axle loads are used for the design and actual operation of such slab-track systems, as well as the speeds.
For Europe the axle load is 25 tons. The ICE trains have axle loads of 20 tons and speeds of up to 200 mph. The Chinese high speed trains have axle loads of 19 tons and speeds up to 220 mph.
If I read the diagram on page 4 correctly, axle loads of 42 tons at 68 mph are possible.Regards, Volker
RMEYou're getting carried away.
Really? You choose the joint spacing so that the tensions from hampered temperature contraction don't exceed the tensile strength. And yes the spacing is about 25''. That is what I meant in my last post. In a foreign language you always what you want to say but never can be sure if you really wrote it.
The tensile strength of a good composed concrete can reach 10% of the compressive strength.
RMEWhat MC is discussing is not so much a tendency for the slabs to 'pull apart' as for the structure as a whole to stringline.
How shall slabs with grouted joints stringline? Or do I understand stringlining differently than you? In the Boegl drawing you see #8 GEWI steel. That is a threaded reinforment steel similar to Lenton steel. GEWI has a cylindrical coarse thread, Lenton a conical fine thread. The corresponding GEWI steel of two slabs are coupled with turnbuckles and nuts (#10) according to the drawing on page 7.
The two grouted recesses act as dowels for transverse forces. Prestressing is only in transversal direction.
The subgrade is a hydraulically bound layer upon a compacted frost protection layer. The slab are erected with a 3cm (1.2'') wide joint which is poured from above with a bitumen-cement grout. When pouring the concrete only the dowels for the rail fasteners are inserted into the steel formwork (page 15, picture top left). The fasterner seats are digitally CNC processed for the required rail fastener and the fastener assembled on the slab. The slabs are stored with the rail fasteners assembled.
On page 5 you can see that the rail seat is already profiled in the formwork. There are only last adjustments necessary.
Boegl only gives the requirements for the subroadbed not the measures.
By the way Boegl designed and produced the precast concrete elements including the Guideways for the maglev train from Shanghai to the airport.Regards, Volker
Paul_D_North_JrThose methods address only the deflection/ displacement (i.e., in the Y and Z directions) at the joint, and not the slopes or angles approaching and leaving the joint. That only guarantees that at any dip at a joint, both sides will be equally far down. Such a loss of support is not good for the ride on the rail above, depending on the depth and length.
Look at the FFL brochure pp.6-7, where they talk about the 'whipping effect' of thermal distortion.
Presumably the tremie grouting procedure after the slabs have been laid will eliminate most of the tendency for heating compression to induce 'low joints' between the slabs, as well as address any tendency for sections (e.g. those formed by controlled cracking at those control joints) to start progressively trying to tilt (like the pavement slabs on I-20)
With respect to loading: the direct-fixation system tested under the cooperative slab-track program received what I thought was considerable HAL testing, which it passed (admittedly in the very consistent TTCI environment) without substantial problem. I was hoping to find a description of Alstom NBT 'suitable for framing' in a link here, but haven't succeeded yet. But there have been a number of results of that system in 'mixed service' with positive results thus far.
ATSFGuySo train tracks will no longer have rocks under them; how will they stay in place?
This is covered in detail in the link Herr Landwehr provided. A couple of the abbreviations used for subgrade materials and methods were not directly familiar to me, but can be reasoned out with a little more reading.
Note the difference between this method of subgrade and track provisioning and the two Class 9 systems tested for Amtrak a few years ago.
So train tracks will no longer have rocks under them,
How will they stay in place?
VOLKER LANDWEHR mudchicken Going back to the concrete tie analogy, you ought to see what happens with unconfined slab track in tension Ballastless track has the same challenges as concrete highways. So the problems are not new and there are solutions: Joint spacings limiting the tensions to values smaller than the concrete's tensile strength.
mudchicken Going back to the concrete tie analogy, you ought to see what happens with unconfined slab track in tension
Ballastless track has the same challenges as concrete highways. So the problems are not new and there are solutions: Joint spacings limiting the tensions to values smaller than the concrete's tensile strength.
You're getting carried away. These precast units have very little 'tensile strength' in the concrete (even where high-early-strength or additives like those in the 'concrete bottle caps' are used) and with specific reference to the Boegl system you can see the very closely-spaced control joints that in fact facilitate controlled tension cracking. Substantially all the longitudinal strength is in the tendoning, as it should be.
What MC is discussing is not so much a tendency for the slabs to 'pull apart' as for the structure as a whole to stringline. When this is resisted only by dead mass or some pathetic attempt at doweling, there will be problems just as there can be when LWR is improperly installed off the proper neutral temperature. One approach Boegl used (see p.12, I think, in the illustration of bridge trackwork) is to incorporate longitudinal keying in the precast units, and rolling or forming appropriate faces in the subgrade.
It will be interesting to see what MC and others have to say about the method Boegl uses for crossing fabrication, and for 'transitions' to conventionally-ballasted track (both of which I thought were well-thought-out from a theoretical design standpoint...)
Note also on p.15 how tuned-mass springing is incorporated in this system (it is apparently inverted compared to mine). I would like to see the precise anchoring and bedding systems used when casting the rail-seat areas in the units, and the device(s) used for finish-grinding the seat areas for fastener-hardware installation (note how the formed seat in the slab units is defined!)
There is an interesting discussion on the conversion of a 100mph line which needed rebuilding due to what I understood as being subgrade instability -- the specific details on how the subgrade was remediated here would be highly interesting.
It helps that Max Boegl is an integrated building-engineering company (perhaps comparable to Koch or Bechtel here) and not just a contractor with some experience in precast unit production.
To avoid misalignment at joints dowels or tongue and groove constructions can be used.
The top-down production has a number of advantages. Being manufactured in precast concrete plants you usually can produce higher concrete strenth parts than in-situ. The rail fastenings can get inserted into the formwork with only little tolerances. On site large slabs are easier to align than single rail fasteners.
You need a good compacted subroadbed for slab track. Slab track is not a rigid system but an elastic slab on elastic foundation.
Slab track is not a new method. In Germany there are about 800 miles especially on high speed rail lines with more than 190 mph. In China the German company Max Boegl built approximately 3,700 miles of their slab system for high speed lines. Part of it was the line Beijing - Shanghai: https://max-boegl.de/en/downloads-en/108-ffb-slab-track-boegl-1/file.html
I think it is an interesting reed with design details and subroadbed requirements. It is just one of a number of systems I choose it here because of the good documentation.
The slab track spreads the wheel loads far better than ballasted track. There is less maintanance needed to keep high speed travel comfortable. The costs for slab track are approximately 40%-50% higher than ballasted track. The maintenance costs are less than 10% of ballasted track. Break even is said to be at about 25 years depending on system and unexpected damages. The life span is an estimated 60 years. Additional disadvantage, the slab track is about 5 dB(A) louder.
The slab track is currently not a solution for every track problem but for special purposes.Regards, Volker
mudchickenGoing back to the concrete tie analogy, you ought to see what happens with unconfined slab track in tension
Ballastless track has the same challenges as concrete highways. So the problems are not new and there are solutions: Joint spacings limiting the tensions to values smaller than the concrete's tensile strength. To avoid misalignment at joints dowels or tongue and groove constructions can be used.
DSchmitt When the Southern Pacific built their mainline across marshland between Fairfield/Suisun and Benicia California the track sank within hours. They kept dumping more rock until the roadbed stabilized. Took years.
When the Southern Pacific built their mainline across marshland between Fairfield/Suisun and Benicia California the track sank within hours. They kept dumping more rock until the roadbed stabilized. Took years.
I believe Stephenson initially tried dumping rock in Chat Moss to form a firm foundation for his railway, but the rock just sank without trace so he had to try another strategy. No doubt SP hoped that the marshland they were faced with wasn't too deep so that dumping rock would form a solid base for their railroad. With modern techniques such as ground radar and seismology the guesswork in these matters would be eliminated.
There are circumstances in which the geology is just so difficult that the ideal construction strategy is - give up. The San Diego and Arizona Railway traversed country in which steep gorges combined with weak, weathered rock and earthquakes. In these circumstances, you can monitor the track continuously for rock falls, subsidence and earth tremors and expect to pay a lot for maintenance and even build diversions in a hurry (e.g. the Goat Canyon trestle) but in the end it may not be worth it.
The tendency today is to pay more attention to the subgrade. Railroads typically devote engineering effort to the track and ballast, while accepting the sub grade as a given to deal with, other than attempting to control surface drainage. A lot of present day railroad grades were carved out before 1900. If fills needed some degree of compaction, they used water jetting saturation to consolidate the soil, eliminate voids, and then relied on drying to further shrink the soil.
For today’s highways, they carefully select fill soil type that is most ideal for achieving compaction and has the proper moisture content for successful compaction. Then they mechanically compact the soil and measure the degree of compaction to make sure it complies with compaction specs. The highway engineering extends entirely through the subgrade. They also install lots of holding ponds, tiling, and culverts to prevent the subgrade fills from becoming saturated.
A modern railroad with its intense loading no longer has the luxury of confining their engineering to just the track and ballast, while ignoring the subgrade. I doubt that the current state of the art for track construction has reached the ultimate perfection in terms of engineering or economics.
Both ballasted track and the tubular modular track system require stable subgrade to the extent that the track foundation is rigid in its supporting plane; and to the extent that that supporting rigid plane is of sufficient area to spread the weight out onto enough area of subgrade to support the trains. In other words, a subgrade can be relatively soft and flexible if the track structure base footprint is a relatively large and rigid plane. The softer the subgrade, the more area of rigid track foot base that is needed.
What ballasted track, loading is transferred from the ties into the ballast, and the bottom of the ballast transfers the loading into the subgrade. But there is no rigidity to the track foundation base at the bottom of the ballast. There is only some degree of stiffness in the ballast layer due to the interlocking nature of the rock aggregate.
With track on a concrete panel, the load is transferred to the subgrade by a rigid base footprint of the track (assuming that the panel is rigid). With the support structure of tubular modular track, those features also form a relatively rigid track foundation base. Therefore, these systems will “float” the track loading over relatively poor supporting subgrade –if- they also provide sufficient area of contact with the subgrade.
However, it may be more cost effective to properly engineer the subgrade fills than to sufficiently enlarge the track base footprint area. That would mean that if a railroad had to cross a swamp, it may be cheaper to excavate and remove the poor soil, and fill with compacted granular soil rather than build a broad footprint of track structure to float the train loading over boggy ground.
I tried to sell my two cents worth, but no one would give me a plug nickel for it.
I don't have a leg to stand on.
BaltACD samfp1943 MC mentioned seasonal problems. When I leved in SE Kansas, it seemed that UPRR was constantly, hauling large rocks to a place about a mile sout of Parsons. It was apparently, a low marshy spot,and had been for years! The KATY laid that line down in the late 1800's, one would think that they would have had that problem conquored a long time ago? But UP is apparently, still regularly dealing with it? Seems as if the "NEW Techinques, noted by IM are just attempts to reinvent "the wheel"? I guess that any gains where ROW MOW is concerned are just simply, incremental? You gain/you loose? MC is right in what he stated about Mother Nature...! When you build across swamps, no matter what you do or when you do it, it remains a swamp unless you have the ability to drain ALL of it to bedrock and prevent the wet lands effects that eminate from property your company does not own.
samfp1943 MC mentioned seasonal problems. When I leved in SE Kansas, it seemed that UPRR was constantly, hauling large rocks to a place about a mile sout of Parsons. It was apparently, a low marshy spot,and had been for years! The KATY laid that line down in the late 1800's, one would think that they would have had that problem conquored a long time ago? But UP is apparently, still regularly dealing with it? Seems as if the "NEW Techinques, noted by IM are just attempts to reinvent "the wheel"? I guess that any gains where ROW MOW is concerned are just simply, incremental? You gain/you loose? MC is right in what he stated about Mother Nature...!
Seems as if the "NEW Techinques, noted by IM are just attempts to reinvent "the wheel"? I guess that any gains where ROW MOW is concerned are just simply, incremental? You gain/you loose?
MC is right in what he stated about Mother Nature...!
When you build across swamps, no matter what you do or when you do it, it remains a swamp unless you have the ability to drain ALL of it to bedrock and prevent the wet lands effects that eminate from property your company does not own.
Given soft ground and shallow foundations, a wooden shack will fare better than a fine stone-built mansion. It would be pretty silly to replace conventional track on the Napoleon, Defiance and Western RR with slab track!
There are two alternatives to draining a swamp before building on it:
(i) Drive piles down to firm ground and build a platform on top of the piles, and then build on this platform. The European cities of Amsterdam and Venice were built in this way. I believe high speed lines in the Netherlands use a similar technique.
(ii) Build what effectively is a raft on top of the swamp, and put your mansion, road, railway or whatever on top of this. In the 1820s George Stephenson was faced with the problem of getting his new railway from Liverpool to Manchester, in England, across Chat Moss. Chat Moss is a peat bog up to around 35 feet deep. Stephenson solved the problem by constructing a raft from brushwood, heather, timber etc. and building his line on top of it. The line opened in 1830 and is still very much in use, still on the original raft (the acids and lack of oxygen in the peat probably prevent decay).
Plastics are useful for both (i) and (ii) because of their low density, good strength for weight and resistance to chemicals and rot. Polystyrene blocks are often used for embankments on weak ground and for waterlogged ground like swamps, would also be buoyant.
Another case of "It aint prototype" model railroad becoming real.
Going back to the concrete tie analogy, you ought to see what happens with unconfined slab track in tension
That's going to be ugly.
"No soup for you!" - Yev Kassem (from Seinfeld)
Sam: MKT had a penchant for building in some less than choice locations. That's why their original main died an early death and they couldn't move over to MoPac trackage rights quick enough in western MO / southeastern KS. (even before the consolidation)
ps- the funny looking rip-rap on the sides of the fill around El Dorado KS is the remains of that ATSF slab track experiment of the late 70's, early 80's. .... Railroads will study a technology long and hard before allowing it in common/ universal use. They've seen what can happen with unproven technology over and over again. PTC was forced on the industry and that story is still playing out.
samfp1943MC mentioned seasonal problems. When I leved in SE Kansas, it seemed that UPRR was constantly, hauling large rocks to a place about a mile sout of Parsons. It was apparently, a low marshy spot,and had been for years! The KATY laid that line down in the late 1800's, one would think that they would have had that problem conquored a long time ago? But UP is apparently, still regularly dealing with it? Seems as if the "NEW Techinques, noted by IM are just attempts to reinvent "the wheel"? I guess that any gains where ROW MOW is concerned are just simply, incremental? You gain/you loose? MC is right in what he stated about Mother Nature...!
Paul_D_North_Jr "Weak, marginal, or too-variable subgrade bearing capacity - including expansive soils, and the heavy loads, high impact, and vibrations caused by US railroad equipment at speed, are severe challenges to any of these systems. Concrete ties - a good idea with some valid benefits - have demonstrated the sometimes-truism that "Every advantage has a disadvantage". A lot of money and faith was put into them, only to find out some years later that abrasion under the rail seat was causing wide gage and stability problems - and this weakness is ongoing. Not enough to completely negate their added value, but definitely a tarnish on it." - PDN.
"Weak, marginal, or too-variable subgrade bearing capacity - including expansive soils, and the heavy loads, high impact, and vibrations caused by US railroad equipment at speed, are severe challenges to any of these systems.
Concrete ties - a good idea with some valid benefits - have demonstrated the sometimes-truism that "Every advantage has a disadvantage". A lot of money and faith was put into them, only to find out some years later that abrasion under the rail seat was causing wide gage and stability problems - and this weakness is ongoing. Not enough to completely negate their added value, but definitely a tarnish on it."
(*) Railroaders M/W Rule #1 - Mother Nature Is A B__tch!..."
Just an observation: It seems that BNSF in this area seems to cycle their 'Heavy maintenance work' about twice a year, and other MOW functions ( Track Inspection trucks, and other maintenance a couple of more times, a year). I would have aoriginally thought that concrete ties would have been more heavily used, but, it seems they are used in odd places; in bridges, on either end (on and off?) transitions to wooden ties. Same seems to be for switches(?).
About a year ago UPRR (on the OKT sub/ nee:RI ) did a 'major maintenance push'(?) south from Wichita, rails, ties, and rebuilding of road grade crossings, grading and ditching. It seemed they had more equipment than would be used in a RBB&B Circus move.
MC mentioned seasonal problems. When I leved in SE Kansas, it seemed that UPRR was constantly, hauling large rocks to a place about a mile sout of Parsons. It was apparently, a low marshy spot,and had been for years! The KATY laid that line down in the late 1800's, one would think that they would have had that problem conquored a long time ago? But UP is apparently, still regularly dealing with it?
BaltACDMay have been, but the drains got clogged!
Time to call "Rotorouter". LOL.
Norm48327 mudchicken I thought that was Trump's line.
mudchicken
I thought that was Trump's line.
May have been, but the drains got clogged!
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