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Load on Pipeline Crossing Under a Railway Line

05/24/2017 7:43 AM

I ve to provide a 1400 mm dia Mild Steel casing pipe crossing 9 meters under a railway line to carry a pipeline of 900 mm dia. from one side to other. To calculate wall thickness of the casing pipe to withstand the load of the earth overhead as well as the load of the moving train overhead, I need to know lateral pressure on the pipe to ensure it does not buckle. The Diesel railway engine weight is 112.8 tons. and 17 meters long. Has 12 wheels 6 on either side. Each wagon's max. wt. is 83 tons and length 10 meters. The railway line is broad gauge which has a span of 1.676 meters between the rails. Can anyone provide the thk. calc. or let me know at what spread of area the load will get distributed from the top of the embankment to the top of the pipe so the pressure on pipe can be calculated by dividing the load by the area.

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#1

Re: Load on Pipeline Crossing Under a Railway line

05/24/2017 9:27 AM

Try this first:

https://en.wikipedia.org/wiki/Lateral_earth_pressure

Are you sure about buckling of the pipe?

What wall thickness is available for your casing? Do you have many options?

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#2

Re: Load on Pipeline Crossing Under a Railway line

05/24/2017 10:16 AM

If it was me I would be inclined to use standard concrete culvert piping for the load bearing section given its engineered to withstand such loads plus has an extramly long service life compared to mild steel when placed in the ground.

Beyond that I would also l consult with the railway engineers as to what depth and other requirements they may have as well.

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#3

Re: Load on Pipeline Crossing Under a Railway line

05/24/2017 3:34 PM

I imagine the "soil" composition between the railroad bed and your pipe will also be a concern. Swamp, solid granite bedrock, crumbled slate, mafic lava (the cooled variety) and loam top soil will all have different load bearing capabilities that can carry the load around the pipe.

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#4

Re: Load on Pipeline Crossing Under a Railway line

05/25/2017 2:03 AM

For coated or cathodically protected pipe.... .469" nominal thickness...unprotected .531"...minimum yield strength 35k psi...

https://www.cn.ca/-/media/Files/Delivering-Responsibly/Safety/Utility-Installation/pipeline-specs-form-US-0510-en.pdf?la=en

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#5
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Re: Load on Pipeline Crossing Under a Railway line

05/25/2017 2:54 AM

Thought you were having a laugh. I overlooked that decimal following that initial ellipsis.

...

Shouldn't those thicknesses be 0.750" and 0.812", respectively?

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#10
In reply to #5

Re: Load on Pipeline Crossing Under a Railway line

05/25/2017 12:16 PM

Yes....I guess I was looking at 900mm....that's why I include the links, for double checking....good catch

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#6

Re: Load on Pipeline Crossing Under a Railway line

05/25/2017 3:18 AM

Most modern railway organisations will have standardised solutions for this particular application, though usually in pre-formed concrete sections rather than in steel. Maybe it's time to pick up the phone and ask about them with Engineers that actually work in this field, perhaps?

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#7
In reply to #6

Re: Load on Pipeline Crossing Under a Railway line

05/25/2017 10:02 AM

I go along with that. In fact it might be a case of the railway engineering dept refusing to allow you access - and doing the work themselves - and sending you a bill at the end.

If I owned a railway, I would not wanting novices digging tunnels under it.

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#8
In reply to #6

Re: Load on Pipeline Crossing Under a Railway line

05/25/2017 10:14 AM

Anyway, isn't that a good enough reason to attend a networking event? - to get to know people who know where to look things up? After all, not everything is on the internet.

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#9
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Re: Load on Pipeline Crossing Under a Railway line

05/25/2017 10:24 AM

The problem is that everything but clearly indicated as authorized answers are on the internet. Remember, for every AHJ there are millions of bored wannabes and liars that are eager to be heard. Internet search engines put at the top of their searches the popular answer. If your lucky that will be the correct answer.

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#11

Re: Load on Pipeline Crossing Under a Railway line

05/26/2017 4:23 AM

Thanks to all for your comments. I guess I need to go to a consultant who gets clearances / approvals from Railways for such crossings.

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#12

Re: Load on Pipeline Crossing Under a Railway line

05/26/2017 7:26 AM

why not some out of the box idea?

how about using regular steel plates of parabolic shape, placed vertical, facing each other and the 900 mm pipe passing between them?

all the lateral load will be nullified because of shape. soil density varies in different seasons, that's the only problem you have to solve now.

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#13

Re: Load on Pipeline Crossing Under a Railway line

06/02/2017 4:50 AM

The depth of burial also comes into it. The deeper it is, the greater the weight of earth, but the weight of the engine is spread out more.

I agree with others in thinking steel isn't the best choice for the job.

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