How does a track maintenance crew insert a drainage culvert under a busy mainline?
There are several places on the CN line in the Southbend subdivision where the ballast keeps settling due to poor drainage. The cars severely bounce on the loose ballast section. This leads to track fractures. This problem has existed for over a decade in multiple locations. When a auto carrier unit train rolls over these settled ballast points, piercing metallic shreeks and bangs from the bouncing cars can be heard for a mile.
If they have not fixed the problems in over a decade, is it because it takes too much time and effort for the installation of proper drainage through culverts or other means?
When they added the passing siding at Nestle (actually just south of Burlington, the site is near a Nestle chocolate plant), they used a big drill to drill under the roadbed and insert steel culvert pipe(s). Was interesting to watch.
I remember a case in which a jet pump (using a forced stream of water) was used to install a sewer line under a four-lane divided highway without interfering with the traffic. A double-track railroad and a culvert shouldn’t be too much different.
Not sure a culvert is the answer to settling roadbed, though. I’d like to see what our resident Mudchicken says about this. (Sounds to me like they need some serious surfacing, though!)
If it’s a large culvert, the railroad may suspend operation for 6, 12, or 24 hours, to do the work. Belive it or not, it’s often faster (and operationally less intrusive) to just shut the line down for 12 hours, then to spend 48 hours, trying to work between trains.
One thought is to just go ahead and build a bridge over the stretches of land where the rocks and track keep sinking. They keep maintaining the line, but the sinking spots still remain.
Without looking at the site, this sounds much more like a subgrade materials problem than a drainage problem, strictly speaking. The only reasonably permanent solution is to provide drainage – yes, probably a culvert – but also to remove the unstable material far enough down (and without looking at it, I’m not going to say how far that is) so that the load is distributed adequately. The problem is much worse crossing such goop as muskeg, which happens in parts of Canada – there you may have to go several tens of feet with good material to get adequate bearing strength.
As to how to put a culvert under the line? There are a bunch of different ways to do it. Depends on the material, size of culvert, distance to be crossed, access on or outside the right of way, etc. Jacking is one way; boring and slipping a pipe through is another. Sometimes as noted the simplest and quickest thing to do is take the line out of service and go in from the top – but I would think that would be rare these days.
In 1981, we had to install a culvert under a substantial fill on the BN mainline, to carry a pipe across the right-of-way. The fill at that point was about 20-25 feet above the point where we had to install the culvert. The BN Engineering Dept said “no problem” that there were private contractors with equipment similar to well drilling equipment, it just went in sideways and slipped the “casing” in sideways, just as a well driller would do. That’s how we did it. BN approved the plans, provided an on-site engineer while it was being done, the driller had to stop while trains were passing, and a slow order was put on, but otherwise, there was no interruption in service. It was pretty slick.
The contractor, who did quite a bit of the work apparently (he and the BN engineer obviously knew each other) had a million dollar bond posted.
One of the sinking locations was at Ullery Drive by Indian Lake. A week ago there was much mud oozing up between the rocks that made up the roadbed. More rocks might not do a thing, unless they added asphalt or something built out of concrete that is a combination short bridge and culvert. These spots are bad. I wonder if the CN managers will devise a way fix these sinking roadbeds before there is another derailment.
Similar drilling operation was used by a crew earlier this summer at Dupy. CP crew trucks were around the site - but I believe a contractor brought in the drill. The new installation was bored north of the diamond beneath the CN/WC main. Apparently CP has responsibility for the drainage of the diamond and interchange tracks.
That sinking and oozing, as well as the settling, may not signal the need for a culvert. The ballast isn’t doing its job of draining when it’s fouled by mud, as this place obviously is. The mud came from somewhere–probably from below the ballast, which has caused the settling.
There was (maybe still is) a craze for separating the ballast from the sub-ballast with a layer of geotextiles, something permeable to allow water to pass through but not granular things such as soil. If those are still in vogue, that might be all that’s necessary. As someone else said, drainage is paramount–good ditches alongside the track(s) would probably help in this case–and, yes, culverts if necessary to keep the ditches drained. It would all depend on the lay of the surrounding land.
MC was working far from home, Carl…thanx for pointing out the probable culprit. Beyond fouled ballast, there could be subgrade failure or a problem with ballast pockets.
A good undercutting program followed by shoulder cutting would be a good first step, followed by lime injection or asphalt underlayment in the bad spots. French drains (not culverts) comes next Throwing ballast and surfacing money at a repeat problem is an admission you don’t have adequate maintenance budget (wasting $$$ on shiny new engines and appeasing Wall Street again?) It is a sugar-coating and does not fix the problem.
Subgrade problems , especially persistant ones, require a good geotechnical engineer to help with the solution and coming up with a program to manage and , if possible, eliminate the problem. Increased tonnage tends to speed-up subgrade problems as does concrete ties.
Subgrade problems have been around since day-1, the difference now is there is considerably better technology and understanding of how to deal with wildly different soil types.
The problem could be a natural spring (or springs) which keeps the subgrade wet. I’ve run into that problem on road construction projects. The solution I’ve seen used is one of those proposed by Mudchicken, french drains.
Old technology concept: Napoleon’s boys stole it from the Romans, been around for years. aka-a trench drain…
A basic french drain is a slit trench filled to the top with gravel and small stones. The voids in the rocks carry the water off somewhere with a lower elevation.
Modernized, we use the same trench, line the walls and floor of the trench with filter fabric (to keep dirt fines from plugging up the voids), lay perforated ADS pipe at the bottom of the hole to carry off water faster, backfill with gravel, ballast or some gap-graded material and lay filter fabric with a light covering of dirt on top. (a gravel burrito with a straw on the bottom if you will [C=:-)])