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plastic pipe

plastic pipe

plastic pipe

(OP)
Our client wants to use plastic pipe instead of RCP. The groundwater is within 2' of surface.  I am worried about buoyancy forces lifting the pipe up.  Does anyone know a quick formula to use to see if it will work or how much cover we need.  Thanks

RE: plastic pipe

no quick formula, just sum up the forces
draw your free-body diagram and add up the vectors

downward
weight of pipe
weight of soil over the top

upward
bouyant force

use a safety factor and make sure the resultant is pointing downward

RE: plastic pipe

(OP)
ok
safety factor of 1.5 good enough?

RE: plastic pipe

Just a note....

Don't forget about structures, inlets, catch basins and end sections that will act to secure the pipe. I work in an area with very shallow water tables (Florida) and there is seldom a problem if the structures are not too far apart. Just be careful during construction.

Laura P, P.E.

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