Pile Driving Next to 3rd Rail Power

[muuddfun]

How close to active 3rd rail power have any of you driven piles?

We are driving piles for a bridge bent located between two rail tracks. The rail people do not want to shut off power to two tracks at the same time. They only want to allow one to be taken out of service. We will be maybe two or three feet away from the 3rd rail power, and using a swinging leads. I am not seeing this as a safe operation. 3rd rail power is 600V at 10,000 Amps.

Is there any way to do this safely?

 

[Ron]

No. Pile driving is not watch-building. All it takes is a cable or an inadvertent lead movement and someone gets killed. Don't do it!!

 

[rowingengineer]

agree with Ron.

An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[muuddfun]

Well that is what I have been telling them, but somehow the rail road thinks it can be done safely. I am not sure what planet they are on right now. Hopefully I will find out more tomarow.

Thanks

 

[SlideRuleEra]

If the Railroad company won't listen to you, get the Contractor's insurance company involved - they will likely provide excellent support for your position.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[MiketheEngineer]

Show them how and let them do it. Just kidding.

But it might get a few heads wagging and some people seeing your point of view.

 

[geoman110]

As everyone said before, this is not safe at all. Depending on the subsurface condition and applied loads, can you change the design to use smaller equipment instead of conventional driven piles. For example, if you are driving end-bearing piles, can you switch to Helical piles? If you are using friction piles, can you use micro-piles instead? Both of these substitutes, use much smaller equipment (as small as a bobcat) and may work for your situation.

 

[muuddfun]

Just came from a meeting about how to proceed in the rail yard. The rail company is thinking that if you can drive piles with zero clearance next to a building then why not next to the third rail. Some how they think we can possition the drilling rigs and cranes in such a way as they won't go in the wrong direction. The maximum clearance we have to the dynamic train envelope is about slightly less than 3' with a little less than 5' to the hot rail.

The prime contractor has not involved his pile driving sub in the planning for the rail yard. I spoke to the sub and he is comming tomarrow to another meeting to help sort this out. He was very unhappy when I told him what they were planning for him to do. He will figure out what he can and can't do safely, it his guys who have to do it.

In this project the work is being done for the rail road, but they are not managing the work it is a city project. So 8 or 10 years ago during the beginning stages of plan development this all should have been sorted out, but somehow the rail road has forgotten why the project is being built in the first place and have been slow to figure out how to proceed in this tight area.

I wish we could change the design to something else, but do the manny restrictions it is not possible. That was the first things we looked at was how to change the design, even skip the bent in question, but it couldn't be done.

 

[PEinc]

Was a representative from the railroad's safety department present at the meeting? I can't imagine their own safety guy would be happy driving that close to a hot third rail.

http://www.PeirceEngineering.com

 

[geoman110]

You can tell them that the difference between a building and power line is the spark. If you get too close to a building, it does not hit you with a spark of electricity.

In respect to changing the foundation type, I still do not understand why you cannot change it. If from geotechnical point of view, helical piles and micro-piles are feasible, you can change the foundation type, without changing the super-structure. The bend and anything else would be the same and only the foundation (and possible pile cap) would change.

 

[dgillette]

Is this in the US? I can't imagine OSHA allowing such a thing. One distraction (looking up at the hammer, windblown trash, attractive woman going by on the train, etc.) is all it takes for someone to step wrong and stumble. This sounds insane. Maybe railroad could shutdown the other line from 9 pm to 6 am so you can work at night.

 

[muuddfun]

We have had many problems with the pile installation on this project. After several hundred piles we have a procedure that works, I am very reluctant to change what we have spent million of dollars to find out the hard way, works. I started managing this project about a year and a half ago just when the previous guy bailed out, and that was just when things started to get difficult.

Design started about 8 years ago. Back then they never let our firm get access to drill any borings for the long expanse of the rail areas. So we got stuck with some borings at the river, then some about 700 feet away near the abutment. Total length is slightly short of 2,000 feet. To this day I still do not have any borings in this last area we are now working on.

We looked at many types of foundation options but do to many structural requirements we got stuck with driving 24 inch diameter CISS piles into a boldery riverbed. Micropiles won't give us the lateral values the structural needs. The other problem is the structural can't now change the stiffness response of the footing because most of the rest of the bridge is already being constructed. To change types would not work with his modal response and plastic hinging requirements. We had originally wanted to use CIDH during primary design, but the structural needed the CISS in the end to do the job. Earthquake loads are by far the primary drivers of the loading conditions.

We have already constructed 85 percent of the foundations, but now its the last 15 percent we can't get over. The rail yard has cost 2 years already on the construction schedule, and the project is already running at 50 percent of the bid in change orders. And thats before we even drive a singe foundation pile to start with in the rail yard.

There are too many underground utilities in the rail yard to clear the bents. So we are already having to redesign for about the 10th time the foundations in the yard. We are now having to construct an ecentrically loaded footing. The piles on one side are directly under the pier wall, and then we have to turn the pile cap into a large outrigger to get to the other row of piles used to resist the overturning. Whenever we are short of capacity of the piles then we have been driving extra H piles in between the CISS piles to get a little extra capacity. To date the majority of the problem has been with tension values, but with these ecentric footings we will also have to deal with large compression loads. If I overdrive the CISS piles then I will hit a layer of siltstone about 70 feet down, that won't have nearly the end bearing that I can get in the bouldery gravel layer about 50 feet down. If we drive the piles to short we don't get tension, if i am to long we won't get end bearing and therefore not enough compression, I have a hot rail one one side, and a buried 34 kv traction power duct about 5 feet on the other side of the pile cap. So you can see that I am pined in a very small area with vary narrow windows of what can be done. The rail road made us relocate the pile cap so it would not encroach over the top of the vault for the 34 kv, this is why we now have an ecentric footing. And we can't move the pier wall because it then wouldn't line up with the existing portion of the bridge.

I already asked to skip the bent in question, but it won't work because we have a similar problem at the bent next to it, and we would have to move track, relocate train control ducts, and more hot rail, if I had to double the span, in order to get the footing loads down to something I could accommodate. It is alread difficult enough for that bent.

This project may send me to the funny farm in the end.

Any ideas please. I have already had about 6 geotech Phd's advising me on this project but sometimes they are't as good as all of your collective wisdom and experience. The Contractor has been around for decades and he has built literally thousand of bridges, and he said he hasn't come across one that was this difficult yet.

 

[Ron]

Assuming this is some sort of a municipal "people mover", what about driving the piles between midnight and 6:00 am and/or on weekends? You could then de-activate the third rail and get it done safely.

 

[vulcanhammer]

Let me ask an idiotic, "equipment person" type of question: would fixed leaders help? Many of them can be positioned with a reasonable degree of precision, some even allow for vertical travel of the leaders, if that's helpful. It struck me when you said "swinging leaders" near high tension electrics in tight quarters that this wasn't a good thing to do.

Also: what type of hammer are you using?

http://www.pz27.net

 

[muuddfun]

dgillette

This is California.

Ron

Thats what I am hoping they have in their back pocket if we press them hard enough.

Vulcanhammer

Thats what I need to find out from the pile sub, we have been using a swinging leads so far on this job. Hopefully he has a fixed leads rig that might help some. Thanks

 

[PEinc]

Whether using fixed or swinging leads, you still need to be a certain diatance from an energized power line or, at least, the line needs to be shielded. Using fixed leads may help, but they do not eliminate all of the possible things that could go wrong that close to the third rail.

http://www.PeirceEngineering.com

 

[cargua]

First of all it would be interesting to know why its not possible to turn off both side o railway (service, traffic, electrical reasons or just foolishness)

How many piles are you going to do? maybe doing the job at night while the rail service its closed or almost, would be the solution. (turning it off before)


You are looking for ideas, i have some of them, maybe weird but they are all ideas:

1. I think you should ask for advice to an electrical engineer, because maybe its posible to make a "faraday cage" and all your equipment work inside of it.

2. Maybe its better to deviate the railway (if there's enough space for it).

3. Do the rail people have not electric train (fuel train)? maybe they can use it while you are working at night services. (i know this kind of train exist, because is the one they use in maintenance services)

4. Do a tunnel down the railway, and do the job there. (i know its weird, but it's just an idea)

 

[muuddfun]

Some kind of barrier or shielding might work.

My concern that I expressed to the contractor the other day was that he might not have enough room to construct a barrier. I was thinking of something like a k rail to anchor the bottom and then building some kind of screen wall above that.

Does a faraday cage have to be all the way around, or would partial screening with a metal fence on one side act the same way? My primary concern would be for the crane to move wrong and the hammer or pile to move through any barrier or fall and then come in contact with the rail.

The rail road has three tracks that come into the yard, and they don't want to shut down more than one at a time. They insist that we keep one of the two main tracks open so they can get trains into the yard. We are at a pinch point in there configuration. I think they could give us a window in the daytime when they do not have so many trains coming into the yard to do a shutdown of both tracks for 3 or 4 hours, but so far they have said no. I think they are more worried about there operations than anything else. They pretend to be about safety, but when it comes to something that will effect there operations, then they become blind. They already kicked the contractor out of the yard for a safety violation that was a lot less serious than what we would end up with here, but I guess its all in how it affects them. Maybe after several years of delay from the rail road I am starting to be wary of their motives.

I have made my position clear to the parties involved in writing. We have about a month before this work is scheduled to begin, so we will see how things play out. The resident engineer still thinks he can persuade them to give us some shutdown windows when we get right down to it.

 

[cargua]

I think that you have to ask to the crane guy about the solution too, because he's the one who will work there and he want to work safe too (you could be amazed about the solutions he would give you). But you still have the last word.

Putting a "building" between the work area and the "spark" is the best solution. But you should ask to an electrical engineer about the diferents situations with the spark.

I dont know if the 3rd power rail (im having a doubt with argot), comes by air, a wall or by ground. By ground would be most dangerous situation, because if the ground is wet ... you know.

 

[Zambo]

If you cannot get the power off long enough to drive the piles or divert the track then I think you have to look to the substructure or the superstructure for a solution.

So for a substructure I suggest that you ignore the current geometry of the wall or columns and crosshead (we don't have info about your stucture geometry) just find somewhere that sufficient piles can be driven safely. Then try to design a substructure around the piles. For example you may end up with a substructure which isn't parrallel to the track or even perpendicular to the bridge deck. Once you have a substructure that works then design the superstructure to suit what you have.

If the substructure solution stated above doesn't work then you need to find a superstructure solution. So first design a pile layout and substructure which can be constructed safely and then see what the span is. Then if you are now using pre-tensioned beams you could change to a post-tensioned box sections. If that doesn't work what about a steel truss or cable stayed concrete design?

Once you have a couple of options you can do a quick costing to see if the cost of an operational solution (such as increased closure periods) would be more cost effective.