Minimum PVC cover 1

[scoute]

We are installing 4 inch schedule 40 PVC in an electrical substation at a depth of 30 inches below grade. The purpose of the pipe is to serve as a conduit for electrical relay cables. There will be some heavy traffic driveing over the conduit on a regular basis. I need an equation that will give me the maximum live load, (over the top of the pipe)assuming 90% compaction of fill, or minimum cover necessary
to facilitate heavy semi-trucks moving in the yard.

 

[RWF7437]

This information should be availabble from the pipe maker in the form of maximum and minimum cover tables. 30 inches is probably OK though.

 

[Focht3]

I doubt that you will have any problems - after all, the top of the pipe will be more than 6 pipe diameters below ground. But if pipe failure is a serious concern and you can't put the pipe any deeper, then you might consider backfilling the trench with lean concrete. Stop the concrete 6 to 12 inches from the ground surface - then put base in the top of the trench.



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

 

[cap4000]

Let me first say at 30 inches down you should be ok. The 4 main references you need are by: The Boussineq Formula = Soil pressure stress = 0.477W/H squared. 2nd: Handbook of PVC Pipe Design: 3rd: Refer to Dr.Reynold Watkins Experiments on Buried Coduits. 4th AASHTO Specs. Good Luck.