soil compaction silty sand (very fine sand)/ sandy silt (ML) loader VS vibratory compactor 1

[abds]

We have to backfill for foundation of bldg. backfill material is sandy silt / silty sand ( uniform fine sand) . We have Heavy loader/excavator and vibratory sheep-foot roller for compaction. what would be better for this kind of soil. I prefer vibratory sheep-foot roller but other loader I am looking for openion from experience engg, What would be best for this ?

 

[Ron]

First of all, I would require a better material for backfill. For fill materials, you can specify what you want and you want materials that are easily compacted and not so moisture sensitive. Sandy silts and very silty sands are not good fill materials.

Sheepsfoot compactors are better for clayey materials, not silty materials...they are generally unnecessary for silty materials (and potentially detrimental).

For the materials you've described, I would use static compaction, not vibratory. Your materials are very moisture sensitive and vibratory compaction will exacerbate those conditions.

 

[abds]

THank You Ron.
This is the soil specs, client wanted- close to natural soil. It is weired but they want material having more than 25% fine to prevent seepage under foundation. i have never seen this type of fill requirement for structural fill.

 

[Ron]

How does your client know that there might be "seepage" under the foundation? Are you the contractor? Is there a geotechnical consultant?

What type of "seepage" concerns them? If they are concerned about groundwater seeping upward under the foundation, this is exactly the type of soil you do NOT want!