If you looking for relative compaction then you need to do a sand cone replacement test or a nuclear guage (with your nuke calibrated from your material). Neither of these can be done in a 2m hole unless its wide enough to allow a person and equipment enough space to comfortably do the test.
What's the size of the crushed rock? EireChch is correct unless of course you are dealing with rock large rock sizes.
I am not sure if you are doing this at the base of a hole that has been dug to 2 m depth or ? If it is one that is done to 2 m depth and you are testing the base, you will need to make sure that the sides meet safety requirements as this is deeper than 1.4 m. if the rock size ranges are large - say nominally 0 to 300 mm, then the methods suggested by our mate would not really be applicable and you will need to use a water replacement method such as ASTM D 5030. Remember that the diameter of hole is given in D 5030. For a max size of 300 mm, you need a 2 m diameter hole; 450 mm requires 3 m diameter. Basically the diameter of the ring is 6 to 7 times the maximum stone diameter. There are depth requirements too. So, a lot depends on the maximum size of the stone. Bigger stone requires as larger diameter ring which means if you are doing this at a depth of 2 m, then the hole really needs to be big to accommodate.
Try to keep the hole as vertical as possible. Keep all material removed for determining the mass. When the hole is clean, you would would place a thin plastic film in the hole. Keep it "loose" so that when water is placed the film can deform into the crevices that will be present. D 5030 wants you to "mortar the sides smooth" - which is just not done. Prior to digging the hole you will need to determine the volume of water "in your above ground ring to subtract from the total water used. It is pretty intuitive.
Below gives you the "start" of a large scale water replacement test
I love the picture. Good tool set. Now the OP needs to consider that a sieve analysis of the material, Based on the small cobble sizes--ALL of the material, is next on the list of activities. I would also recommend that quite a few moisture sample be taken during the excavation process.
Hi BigH and EirechCh..I need to find the density at the base of a 2 meter hole already filled with compacted crushed rock 10mm. Also need something quick and easy method to get density, as I need to check the density for 1000 predrilled piles.
Seems like you should have determined the soil density at the base (depth 2 m) of the hole prior to filling with your sand and gravel crushed rock. Guess you could remove the hole's backfill.
What is the base? if clayey, after drilling you could push in (or very lightly tap in) a thin walled steel tube and get the density that way (ASTM Core Cutter method). If sandy at the base, you'll have to go with sand cone or rubber balloon. Using nuclear gauge in a hole 2 m deep would have to be calibrated for the "trench" effect. Issue: OSHA Excavation rules.
Why do you need the density at 2 m depth? What is the criteria for "founding" the piles?
Some years ago I had to assess whether coarse crushed backfill (3/4" to 1-1/2") placed beneath the springline of a large diameter (6-foot) concrete pipe had been sufficiently densified by the contractor. US Bureau of Reclamation had developed a procedure referred to as sleeve density method that was accepted by ASTM to provide a measure of relative compaction. The process involved calibrating the drive resistance of the sleeve into a test box filled with the proposed gravel placed a different degrees of relative compaction. After calibrating the sleeve resistance to driving, the test could be run in the field. Time consuming and costly for average, everyday use.
Since the material was cohesionless and would respond to vibratory compaction, I had the contractor run a 2" diameter concrete vibrator into the backfill at 12 inch spacings to see what happened. When the vibrator started to disappear into the backfill and a cone of depression form around each penetration, the discussion was over. The contractor removed 2 feet ob backfill and vibrated the gravel until the probe could not penetrate the gravel; then he added another 12 inches of gravel and repeated the operation.
I do not think this will work well at all on 2m of backfill; maybe 1m might be workable.
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