I need to grind 2 massive tree stumps that are within 20 feet (linear) of my geo pipes.... The geo is 3 years old, so all the soil has settled. The geo is 3 feet down at minimum. The 2 trees that died are about 20 feet away from the geo field, rather large stumps. Do you think the vibrations from stump grinding will disturb the underground piping ?? also, the stump grinding machine weighs 5000 lbs... which will be driven close to the geo field, but not over. What are your thoughts ??
No worry. Drive the grinder anywhere you want over the field. PE pipe can take significant pressure inside or out. Road construction contractors add fill in layers only several inches thick before compacting because compaction tools and pressure won't transmit down through soil well. 3 year soil is probably well settled, so any surface pressure will have minimal impact at depth. The pressure of the grinder is really only gonna be at or near the tire pressure of the machine (maybe 65 psi)
My concern are the vibrations... transmitting down through the soil... Not so much the weight of the machine. I'm sure the grinder will vibrate the earth quite a ways down.
At that distance, Absolutely no concern. I’m a licensed mechanical engineer with an advanced degree in civil engineering.
ok, but when a freight train passes by my place of business, the tracks are 300-400 feet away. You can definitely feel the vibrations in my building. So all the vibrations are transmitted through the earth... Our building is on a slab. You don't think that affects the piping heat welds ???
No real concern. Strength of heat welds are comparable to the base pipe itself. Vibration in and of itself won’t break plastic. Significant movement of pipe could cause issues, but the existing pipe is anchored in place with dirt that’s been compacted for 3 years. There is virtually no freedom of movement. Just think how much you need to bend a paper clip (distance and amount) before it breaks. The plastic pipe is extremely tough and isn’t moving much at all.
I agree with mtrentw - I don't think there is any concern either. If you truly are worried about driving the equipment near or even over the field, put 2x12s, plywood or some other load distributing material on the soil surface below the wheels to distribute the wheel load across the ground. Drive perpendicular to pipe run and not parallel. Unless there is some big voids in and around the piping (which would mean your heat transfer doesn't work too well), I can't imagine any vibration transmitted to the soil would cause pipe settlement at 3 years out from the trench excavation. If you want to read the background to these opinions, google "Boussinesq curve Fig 2.18 from Buried Pipe Design by Moser". Piping buried 5ft or more below grade should have little to no influence from surface loads (pipe sees ~10% of surface loading). At 3ft depth, you are probably close to 25% of surface loading influence. All of this assumes no load distribution at the ground surface and a concentrated load directly above a buried pipe. Move the load to the side of the pipe and all of this disappears.
If you read every post... I'm not concerned about vehicle weight. I'm concerned about vibrations transmitted through the earth.
This specifically addresses your vibration concern: "Unless there is some big voids in and around the piping (which would mean your heat transfer doesn't work too well), I can't imagine any vibration transmitted to the soil would cause pipe settlement at 3 years out from the trench excavation." My own opinion: I would worry about a point load over your pipe before I would ever worry about vibration from a stump grinder. And as indicated, I think the point load aspect isn't something to worry about either.
The heat transfer isn't done in the horizontal header. It's done in the vertical loop... which is 3' to 250' below grade.
