Statement about SPT
Statement about SPT
(OP)
Hi, how do you interpret this:
"SPT tests shall be conducted continuously to a depth of 4 m, or 4 m below the lowest floor elevation, whichever is greater."
How can you do a "continous SPT"?. I usually see SPTs conducted at 1.5 meters intervals (US practice) or 1 meter intervals (in Japan). I am not sure how the above statement can be accomplished.
"SPT tests shall be conducted continuously to a depth of 4 m, or 4 m below the lowest floor elevation, whichever is greater."
How can you do a "continous SPT"?. I usually see SPTs conducted at 1.5 meters intervals (US practice) or 1 meter intervals (in Japan). I am not sure how the above statement can be accomplished.





RE: Statement about SPT
In general, the sampler is advanced for SPT values, then removed and the hole is cleaned only to the depth of the sampler, not to the next sampling interval as you've noted. The sampler is then advanced for the next SPT.
Yes, technically it is incorrect to call it "continuous" since each SPT will consume at least 18 inches of soil with only 12 inches counting for the SPT....but it's close.
RE: Statement about SPT
RE: Statement about SPT
I agree with you that taking an undisturbed sample for clayey soil is often more beneficial, both for checking soil lenses and for testing.
RE: Statement about SPT
RE: Statement about SPT
RE: Statement about SPT
The method suggested by, "Oldestguy" is not appropraite and inconsistent with ASTM, so we would not allow that in highway work. I've seen it though and may be as old. . .
f-d
ípapß gordo ainÆt no madre flaca!
RE: Statement about SPT
RE: Statement about SPT
RE: Statement about SPT
That's besides the point. I would suggest to the client that the thin-walled steel tube sampler is a more appropriate method of obtaining samples as well as giving a value (either by miniature lab vanes in the tip) or unconfined or triaxial testing for the undrained shear strengths as the OP is in clayey materials. Sometimes those who specify should leave the judgement to the geotechnical "expert".
When I was working in India, they would take an SPT at the surface, then a shelby at a depth of 3 m, then SPT at 6 m, etc. - really not good for what we were needing. I wanted to get a handle on the upper 6 m and 2 tests were not enough. As we were using 100 mm thin walled tubes, I would push a tube at, say, 1 m (1 to 1.45), then do an split spoon sampler (SPT) through the hole formed by the thin walled tube fomr 1.45 to 1.90. Drill to 2 m and do the same again. This way I got 6 thin walled samples and 6 disturbed samples (with SPT) in the first 7 m of the site. The bottom line is that we adjusted to the site conditions and didn't follow "standard" or "specified" protocol just to please when the protocols were not suitable.
RE: Statement about SPT
RE: Statement about SPT
In hard or gravelly soils, I have driven a 24" long 'California' Sampler (w/liners) & then a 24" SPT in the existing hole, then auger out to clean.
Beware of trying to run a Shelby immediately beneath a drive, unless you are aware of what can be happening in the soil in front of the drive head. I have had a few surprises.
RE: Statement about SPT
RE: Statement about SPT
RE: Statement about SPT
p.s., I got gray hair too!
f-d
ípapß gordo ainÆt no madre flaca!
RE: Statement about SPT
f-d, 20 ft deep hand auger should be tough, what tools did you use?