Compaction test for backfilling works using sand

[dewins]

Is there an ASTM standard referring on this? EPC contractor preferred to use sand saying there is no standard test and visual inspection is enough. Sometimes, soil will be mixed with sand as binder and will not conduct FDT either.

There is something wrong I think. Please enlighten us.

 

[dik]

I have the attached in my files... seems reasonable, but, don't know the source.

Dik

 

[BigH]

I am presuming it is a relatively clean sand with less than 15 % passing the #200 sieve. By rights, the relative density is the way to go (ASTM has two specs on this - one for maximum density (D4253 using vibrating table) and one for minimum density (D4254); British Stds (BS 1377 Pt 4 Section 4 using a vibrating hammer) also has specs for relative density.) As has been pointed out in a number of geotechnical threads, many (perhaps most) laboratories do not have the equipment to carry out the relative density test. As a result, the Proctor tests are still used. When doing this, the sand will be relatively flat across the water contents and when above the optimum, you will probably see water seeping out the base of the Proctor mold.

One test that can be done is the Ontario Ministry of Transportation test where the volume of the field relative compaction is determined as: (1) density hole is determined by water balloon or sand cone method, (b) the soil removed is then adjusted in moisture content to "optimum" (need an experienced soil tech or engineer) and then, (c) the soil is compacted into the Proctor mold where based on the field hole volume there is a dipstick that permits the number of blows to be adjusted to give the Proctor energy. (d) The volume in the mould is then determined via a scale on the dipstick and (e) a comparison is made of the field hole volume and the Proctor volume to give the "% relative compaction". I used this method back in the 1970s - it works well but was time consuming.

Given that you will be likely doing a Proctor I would suggest that, to get a better handled on the actual relative compaction, the previous layer be tested. Due to the sand confinement issues, it is better not to test the layer you are placing but the previous layer - then, follow the progression in similar fashion until the surface. If the surface remains as "sand", the relative compaction will have little meaning after a few days in the hot sun . . .

At least, this is my take on the issue posed.

 

[oldestguy]

Sounds like the contractor is trying to pull something figuring you may accept it. While the relative density method may be preferred by some, I know that many a sand fill job works out OK using the usual Proctor compaction in the lab and field density tests on the job. ASTM tests apply then, such as D1557 . The lab test has problems (with sample shearing all around, etc), but the numbers usually work out fine for an acceptable product. Hire a testing lab and be done with it. Depending on the use for the fill, maybe 90% compaction may be adequate for simple backfill with nothing special on top.

 

[Ron]

Agree with BigH and OldestGuy.....Proctor (Moisture-Density Relationship of Soil or Soil-Aggregate Mixtures) test will likely be used. I've used same on thousands of cubic yards of fill material in coastal plains soils.....works fine. As BigH noted, the M-D relationship curve will sometimes be relatively flat, indicating that the particular soil is not so moisture sensitive; however, confinement is critical as such soils usually have accompanying low stability. Agree with BigH's note that you should not test for field density at the surface in sands....they become "fluffed" from drying during compaction and will often show lower density in this situation.