> To prevent this, a big part of railway maintenance involves digging out all the stones, washing them to get rid of sand and soil, and putting them back.
This is called "ballast cleaning" if anyone wants to do a search:
This is called "ballast cleaning" if anyone wants to do a search:
- Removing the ballast from a section at a time to do the cleaning means that the rails and sleepers are floating in the air (~1:30 to 2:35)
- They're doing all this work, including transferring waste to another train, underneath catenary wires. low clearance!! (3:40 to 5:20)
Also important to note, they aren't so much washing the stones (though that may be part of the process), they're sieving (grading) the stones to remove everything that's under a specific size (looks like they're removing everything that passes a ~25mm/1" sieve, but scale in a video can be deceiving). Rail ballast is very uniformly graded, i.e. every piece of aggregate is about the same size. Vibrations over time will cause edges of the stones to chip and wear down, with these chips contaminating the ballast. It also leads to rounding of the aggregate, so there's less interlock between the particles.
I'd never considered how much "it helps to have rail, to replace rail" impacted the process -- but it makes sense as everything is incredibly heavy! (Rails, sleepers, aggregate)
From that perspective, of course you'd excavate and clean the track ballast while you're also on the same track. And same with sleeper and track replacement.
Granular gradation is still a major part of modern roadway construction, there are just certain standards that are very typical so they get used without too much thought required. For some applications a visual inspection is enough, but there's generally some standard proportion of sieve analysis required (eg. 1 test per 10000tonne produced), along with proctor tests (to determine maximum dry density) and frequent nuclear densitometry. I've even seen loads of aggregate get rejected due to the large aggregate being too oblongated.
When you get into concrete or asphalt mix design, the aggregate standards can be even more strict - chemical makeup of the stone can be important to avoid alkali-silica reaction; minimizing fines increases the strength of asphalt mix but creates a tougher riding surface; etc etc etc.
Planes, for example, can share the same geographic location -- just at different altitudes; e.g. 25000 ft vs 33000 ft vs 45000 ft., etc. After a certain altitude there isn't anything. No clouds, no birds, just air; set your auto-pilot and go. Takeoff and Landing can be hairy, and you gotta worry about mountains, but that's about it. A basic radar makes it easy to see, and not hard to broadcast by radio.
Same basic idea for space. Gotta get out of orbit and not get cooked by radiation, but otherwise there is a whole lotta empty, and it's not hard to see what's going on with things like radar.
On the ground it ain't so simple. Someone stuck on a rail, avalances, bridge collapses, hills vs inclines, snow / ice / rain / high-winds, and no ability to multiplex, so scheduling gets even harder since there are only so many ways into or out of a location. Trains full of high explosives or toxic chems drive right through downtown areas, often multiple times a day. From a crime and security perspective, airports are locked down pretty hard, while most people could probably just drive to a siding near them and fuck around; you can derail a train with a $400 block of steel you can order online. Communication and signal loss is also way more complicated, esp. if you're going through a mountainous or remote area.
Also, disappointing they didn't actually show the new railstock being laid, just the ballast and sleepers :/
Caltrain outsources much of their maintenance of way work, and it shows.
[1] For some value of "they". I don't know if Caltrain does it that way; most mainline US railroads do.
[2] That is, within a few days. Not necessarily within the time of someone hanging around to watch.
https://www.youtube.com/watch?v=vINzBkK1d-k
Note that the ballast hoppers have a solar panel on them to charge a battery, which runs a motor to actuate the hopper doors. Much better than a couple of guys with a wrench.
> In the 19th century and early 20th century, ballast was shoveled or forked, then screened by hand using portable devices.
No-one asked, but ... I worked at a power station one Summer, my job was to clean the filters at the bottom of the cooling tower. The filter was a stack of plastic bricks; each brick about 1m x 1m x 2m that were a mesh of orthogonal perforated plastic panels with a spacing of maybe 8cm or so. The filter was stacked about 5 "bricks" deep. We washed the bricks under a running hose of about 20cm diameter, standing in water all day; shaking out the mud. The bricks were heavy because they were full of what seemed like river mud. The detritus from the bricks fell down into the pond below the cooling tower, about 20m beneath us. Small skid-steer cat loaders dug out the pond.
I had a runner's build and was being paid £2.70 an hour (late 1990s); the other guys had weight-lifter builds and were on >£10 (they travelled around the country doing the same job, there wage was good money for low-skilled work at the time). I found out that the agency were being paid about £10 for me ... stood in dirty water all day, with the fall risk, the low wage, ... wasn't great. Then I had to quit because of injury after a few weeks. Knee was never the same.
You have a valid point, they were treated like shit but talk about broad-strokes...
The workers seem to be wearing the amount of PPE that I'd want if I was just walking along downwind, but nowhere near the amount I'd want if I was working in the thick of things 8 hours a day. I wonder what their lung disease rates are like.
Still is. There is even an EU exception to the ban because no replacement was good enough.