compaction testing by feel
compaction testing by feel
(OP)
Sorry in advance if this isn't the appropriate activity area for this thread. I'm doing some utility removal beneath a concrete slab on grade. It's a small area 5'x5'x~4'D. I want to backfill in 8" lifts and achieve a 95% MDD compaction. The replacement pad will be ~5" thick with #4 bar 12" oc each direction placed mid-depth. The pad will be dowelled into the existing with two #4 bar on each side embedded 8" with epoxy. The area gets some vehicular traffic. What kinds of manual field tests are done to see if the soil is compacted enough? I have used a boot technique. I kick or grind my boot on the sub grade and if I can make an impression with moderate effort it needs to be compacted more. I've only done this as a pretest to the actual ASTM testing and so far have had good results. This time there will be no ASTM testing. Please don't ask why; right, wrong or different, that's just the way it's going to be. Looking for feedback if anyone else does something similar or different also with good results.





RE: compaction testing by feel
First try it on a known suitable soil area to get some idea of how it works. Several firms that I know of use this along with regular testing to quickly assess a large area before testing with better methods. I've done it many times with no other "testing" to approve a footing excavation as OK.. Call it the "T" test. It is more impressive than using an umbrella.
RE: compaction testing by feel
RE: compaction testing by feel
RE: compaction testing by feel
RE: compaction testing by feel
One comment on your concrete repair. I would suggest using a smooth dowel not deformed rebar. You need stiffeness for the load transfer and a smooth bar is considerably stiffer than deformed bars.
Mike Lambert
RE: compaction testing by feel
RE: compaction testing by feel
However you do it, physically manipulating the soil is a legitimate way of gaining a "feeling" for its properties. I use a T-handle soil sampler to probe and sample the soil or fill below the surface. The resistance to pushing the sampler in gives me an idea of its consistency/relative density, and I get a soil sample that I can examine further. It lets me quickly "look" another 18" to 24" below the surface.
For your specific situation, the relatively small volume of the excavation, and the lack of testing, makes me think that that you should consider backfilling with a material that doesn't need much compaction effort to develop good engineering properties with respect to settlement, shear strength, and bearing capacity. For example, you could use a well-graded sand, will-graded crushed limestone, or flowable fill. You may also need to line the excavation with a geotextile to separate a fine-grained subgrade from a courser-grained fill. This approach may increase cost, but it should reduce risk. Clients should realize that reducing costs by eliminating testing and engineering involvement doesn't necessarily save money in the long run, but it does increase risk to the owner, contractor, and professionals involved.
If you ever have a bad feeling about a situation, sample and test at your own cost to cover yourself and others involved. You'll sleep better.
RE: compaction testing by feel
I have no problem using the #5 rebar, or t-handle bar for natural soils when I have boring data to relate the field conditions.
f-d
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