use of controlled density fill in silo floors

huangyhg

use of controlled density fill in silo floors
does anyone have experience in the use of controlled density fill (cdf) where the depth of the fill will be 11'-0"+-?  we are designing the tunnel for the reclaimer and floor slab for a 55' dia.x112' high grain by-product silo.  they want the floor slab on the cdf rather than constructing a floor.  load will be 3500 psf.  
my questions are:
-what strength of cdf do we need?
-is there any special concerns about the ring around the perimeter supporting the end of the reclaimer (5k load)?
-should this be poured in lifts each lift will have a chance to set up (water has no where to go)?  cdf will be poured over a matt foundation?
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flowable fill or excavatable fill comes in a variety of strengths, 10 psi to 100 psi. the 3500 psf requirement would lead me to specify 50 psi fill for a safety factor of two. the deepest flowable fill that i have used was around a 72 inch diameter casing, approximately 8' deep.  the flowable fill supported construction equipment, (scrapers and motorgraders), after 36 hours.  the soils surrounding the fill were permeable, sands and silts.
conatact a geotechnical engineer to discuss this.