I was wondering about concrete ties. What happens when a wheel drops off the rail ? A wooden tie can survive a wheel rolling on it. Can a concrete tie survive a car rolling (or bouncing along) over the top of it or will it be ruined?
The question is better stated: “does the fastening hardware survive?”…If the steel connections for the DE Clip or Pandrol are destroyed, then the concrete tie is useless. Becomes a piece of big rip-rap or a fixture in a parking lot.
The concrete used in those concrete ties is a special high-early polymer concrete mix…incredidibly tough stuff.
My understanding was quite simple: any concrete tie involved with a derailment was replaced. I wouldn’t think it would matter that much whether or not the tie was polymer-bonded, used high early strength mix, was heat-cured, is post-tensioned laterally, whatever – the line impact of a flange will almost certainly crack it along the line of contact, much as a multiton glass cutter would. There’s little or no elastic damping in the tie-to-ballast interface, so any energy won’t be absorbed and controlled as it is with the Pandrol/pad system between rail and tie.
Safety concerns would indicate that a cracked tie be pulled, at the very least for inspection. I would guess that there are methods of tremie or grout injection that could fix cracked ties… but the cost of doing so might be more than simply pulling a new, good tie from stores and getting rid of the ‘busted’ one.
mudchicken (and others if interested): precisely HOW are modern concrete ties assessed for damage, and handled if damage is found?
If there is a crack or a break, the tie is gone. Surface damage is watched for hairline cracks. If the tie either side is OK, the bad tie may wait a while to pulled out. (with a backhoe)…tie rules in 49CFR213 do not descriminate between wood, concrete or steel and basically say if it is not broken through, holds gage and surface, the fastenings are effective, works as designed and is not seriously worn - Leave it alone (good tie)
Again these rascals are tough & really hard to break
We could use one over on the diner about now.[}:)]
On topic, however, how is the decision made to use concrete vs wood? I know that $$ are almost always the driving force, so what tips the balance?
Tonnage in MGT
So they can survive?
There are plenty of concrete ties out there with surface damage not worth condemning.
If it’s chipped out to the point I can see reinforcing steel or new cracks it will be scheduled to be replaced before failure, otherwise I’m gonna focus my efforts, limited assets and people on things more likely to bite me when they fail first.
I saw a section of track with concrete ties that had been removed due to derailment damage. Some of the ties were just scratched or scored. Some of the ties had damage so deep that the rebar showed and one tie had all the concrete broken away from a section - just leaving the rebar. The temporary fix was to spike in 3 or 4 wood ties between the worse of the damaged concrete ties. The final fix was to cut out about 50 to 60 feet of track and weld in a replacement section. The replacement also had concrete ties.
dd
Gottcha, thanks for the info MC.
dd partly answered my question. Can wood ties and concrete ties be mixed?
Can be mixed, BUT the timber tieswill degrade faster and the subgrade will start to fail in funky places because of inconsistent track modulus. (stiff-flex-flex-stiff-stiff-flex)
Dirtyfeathers,
Way back in the last millenium when I was actively railroading, there was a track condition that we refered to as “memory”.
My understanding was that during track repair and resurfacing, unless a track is thoroughly worked down to as much as three feet below the top of rail (TOR), the “memory” of previous defects (low spots, etc), would eventually re-emerge in the ‘repaired’ section.
Questions: Was (is) this true? And if so, how do you prevent it from happening?
Q1 - Is this true?
A1-Yes, you can have “memory” in subgrade creating mudholes and softspots, and in jointed rail you have endbatter and joint memory.
Q2-And if so, how do you prevent it from happening…
A2a (subgrade memory) Mr. Undercutter and French drains (remember drainage- drainage-drainage from earlier posts?) Dumping ballast and surfacing only postpones (sugarcoats) the problem…That is treating the result, but not attacking the cause.
A2b (joint memory)- joint rail bending, new support ties, tamping under the ties and assuring drainage, welding/building up the end battered rail & chipped sections, bring out a bolt machine & new bolts, stiffer angle bars (6 hole vs. 4 hole) and replacing worn bars that no longer match the rail section.
O gallinus asperatus:
Is there presently any effective use being made of vaults (coupled to French drains, etc.) to provide quick and effective drainage of ballast and subgrade in low spots? And, if so, is there any special construction needed for lateral stability or resistance to perimeter settling?
Vaults won’t be found except around tunnels (a pain to maintain)
More likely you will find ballast wrapped in filter fabric, gabions or HDPE slotted drain in a sock (ADS or Hanson). If it fails, just rip it out and start a new one.
rough chicken?
no, intended to be “bemudded chicken” (Also, as a sort of pun, ‘made devoid of hope’ if you’re not too much of a stickler for perfect grammar, ;-})
I was using the word in the sense of ‘ground that’s tough for going over’. (Remember that phrase so appropriate for MOW… and eerily appropriate, perhaps, for recent forum posts involving a certain spbed and Jim… "per aspera ad astra’?
A more precise word might have been “caenosus.” I’m SURE, however, that “lutulentus” would NOT apply!
Wow, give this thread a 9.2 on the education factor. Good info. Ansewer alot of those “I wonder…” questions I had.
Best regards
John k
Replacing damaged Concrete ties is one thing.
However dont forget that a lot of the derailments happen around switches.
And there are more and more switches around with Concrete ties!!.
THAT`S “fun” to replace!!
Know it, since I have worked for the track departement.
I’ve seen some recycled landscape timbers that are supposed to outlast any type of treated wood. These were very dense and hard to cut. Are Any RR’s using recycled ties and how do they compare?