Soil Friction 1

[B.L.Smith]

Dear Frineds

I'm not a civil eng. and I have a basic question:

Suppose two same material and density pipes:
1- A 50 meters carbon steel pipe on 5 steel pipe support.
2- A 50 meters carbon steel pipe on the dry ground(not buried).
which of them does need greater force for moving?

 

[msquared48]

Steel has a lower coefficient of friction than earth, so I would say the earth application would take the greater force to move, either dragging the pipe or rolling it.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[B.L.Smith]

what is the minimum friction coefficient between soil and C.S pipe?
Does friction coefficient depend on soil compaction(proctor number)?

 

[GeoPaveTraffic]

What kind of soil?

Yes the coefficient will depend, to a greater or lesser extent, on soil type.

Mike Lambert

 

[molerat2210]

There is a lot that goes into design of thrust restraint for buried piping. Are we talking about thrust restaint? The question is not clear at all? Are we talking about soil-pipe interface angle for design of restrained joint pipeline?

Pipe material and pipe envelope backfill material would be determining factors for the inteface friction angle. Research organizations such as DIPRA have publised values for this.

 

[cvg]

flanges or pipe joints will be a controlling factor on the ground. they dig into the soil when you try and drag the pipe. fully welded pipe will not have this issue. on pipe stands, unless the pipe is connected to the supports there will be much less frictional force than on the ground. roller stands will have virtually no friction.

 

[B.L.Smith]

Molerat,

Suppose that the pipe movement is due to thermal expansion of the pipe.

 

[molerat2210]

Brad,

Pipe thrust results at pipe bends, valves, reducers and line stops for pressure pipes. These forces need to be calculated and restrained by the appropriate method. This is why pipeline designer ask questions like: "what is coffecient of friction for the soil/pipe interface".

In the water pipeline design world we use restrained joint pipelines or thrust blocks to resist thrust forces. Sometimes, we need to use batter piles to support the thrust blocks. Thrust forces can be very large depending on the pressure and diameter. Improperly restained pipes can rupture, do lots of damage and result in loss of life. Calculation and design of pipe retraint can get complex due to geometry of multiple bends in a short distance (i.e., become three dimensional problem).