High thermal conductivity backfill

[LittleInch]

Hi,

I tried this question in the electric power forum as it seems to be stuff they use sometimes to reduce cable heating, see

http://www.eng-tips.com/viewthread.cfm?qid=394527

However I didn't really get much traction. The design is pretty much fixed, what I am looking for is ideas and experience of improving the thermal conductivity of soil, maybe using bentonite?

Trying this form or if anyone can advise a better one then please let me know.

Many thanks, LI

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[thaidavid40]

@LittleInch,
When I was managing the design of the DAGIR Training Range out at Ft. Bliss, we ran into this problem there. The native soils and rock we were trenching in there for the MV cabling had a naturally high thermal rho factor (as it was also perpetually dry). We looked into site-crushing trenched materials to produce a "crusher run" material for use as a thermal backfill, but it didn't pan out (pun intended!). If I remember correctly, we ended up using a site-mixed fluidized thermal backfill (FTB) for the majority of the buried power cabling. Be sure not to add too much cement powder to the FTB, or it will be next to impossible to excavate in the future for repairs!
Good luck,
Dave

Thaidavid

 

[oldestguy]

Be careful with soil types that may "attract" water and also may then develop frost lenses, with resulting heave. That heave may lift your facility and destroy it. Low frost heave soils are low in silt, preferably none. You may have to arrange things that no water can reach the frozen ground. I'd think dealing with water is more your problem than thermal conductivity. Involving someone who deals with arctic soil conditions may be needed.