Resisting Force on Pipe

[Trackfiend]

I've been going over some structural problems (situtations) for my own learning pleasure and am hoping that this post is in the right forum.

There is an existing run of pipe (x amount of length) that I would like to remove from under a canal. The soil is clay with varying shear strengths of 0.3-1.5 kips per square foot, depending on the elevation. I am merely looking for the resistive force that would have to be overcome in order to pull this pipe out of the ground. Assuming the soil is clay, the pipe is polyethylene, and the pull is horizontal, how would I approach this? Forgive me if this seems simple, but I deal mainly with hydraulics and hydrology, but like to brush up on structural from time to time. Thanks.

 

[Trackfiend]

I again must apologize. It seems that this is a more complicated problem then I first thought and not enough information was given in the first post. I've been reading over various theories (critical state & steady state) and trying to dig into the relationship between shear strength and cohesion (with clayey soils). I guess I should have investigated this further before posting. Thanks anyways.

 

[ishvaaag]

One would need to know the adhesion of the polyethylene to the clayey soil. If lesser than the actual shear strength Su, you wouldn't need to overcome the whole shear strength at the perimeter. So for your worse data you should expect no less than 2·PI·R·Length·Su, or integration of the same. To be pulled out, straight, you also would need clamping force of this value and that the tensile strength of the polyethylene is enough to stand such tension.

R is the outer radius, or somewhat more, and better count also on some friction coming from the clayey soils, got better from data, and to be added to the pulling force.

It may facilitate the works that being plastic will try to reduce the diameter upon pulling, to the risk of knocking machine and people operating the pull action.

Since we are by now talking of overcoming the brute shear strength of the clay along some length, being somewhat curved wouldn't mean much to the pull force, except perhaps the fact of the pullout being at some moment more brusque from the hook anchor action at earlier states of lesser deformation from lower pull.