Correlation between SPT and Clay Properties
Correlation between SPT and Clay Properties
(OP)
Hi
Anyone has the Stroud (1974) and Stroud and Butler (1975) papers on the correlation between SPT and undrained shear strength and volume of compressibility?
Stroud (1974) The standard penetration test in insensitive clays and soft rocks
Stroud and Butler (1975) The standard penetration test and the engineering properties of glacial materials
Any idea how reliable are these correlations? Any other correlations that you normally use in your design? I am trying to estimate the pile group settlement and ultimate capacity. All I have right now is the SPT-N data.
Thanks.
Anyone has the Stroud (1974) and Stroud and Butler (1975) papers on the correlation between SPT and undrained shear strength and volume of compressibility?
Stroud (1974) The standard penetration test in insensitive clays and soft rocks
Stroud and Butler (1975) The standard penetration test and the engineering properties of glacial materials
Any idea how reliable are these correlations? Any other correlations that you normally use in your design? I am trying to estimate the pile group settlement and ultimate capacity. All I have right now is the SPT-N data.
Thanks.





RE: Correlation between SPT and Clay Properties
See attached technical note which questions the use of SPTs in clays.
Although it raises questions, correlation of N values to undrained shear strength is widely used in the UK. I have even seen engineers use N values to determine undrained shear strength over shear vanes that directly measure undrained shear strength in the same borehole....
RE: Correlation between SPT and Clay Properties
Anyone who has been following developments in site investigation techniques over the last 30 or so years knows that there are more reliable in situ tests than the SPT; the SPT is arguably the least reliable in situ test. Cost is obviously an important factor, but once you take into account the time taken to do a load of SPTs, other techniques (e.g. CPTs) are actually quite cost effective. If the cost of unreliable data on a design is also considered (e.g. in terms of additional conservatisms needed in the design due to the reduced reliability of the input data), then SPTs just aren't cost effective.
RE: Correlation between SPT and Clay Properties
I go both ways.
f-d
ípapß gordo ainÆt no madre flaca!
RE: Correlation between SPT and Clay Properties
Can you attach the file?
thanks, Dik
RE: Correlation between SPT and Clay Properties
LRJ - Yes I would have to agree with you. A colleague of mine once told me that those were the most expensive words in business "we've always done it that way". SPTs have do have an advantage of being able to penetrate most soils. We use to have problems with CPTs when we had shallow gravel layers, i think they would call refusal as soon as they hit a qc of 30MPa . When you have to start pre drilling the cost goes up. Doing SPTs every 1.5m was the norm too where i worked. I asked one day for SPTs every 1m and the driller looked at me in shock. Again, "they had always done SPTs every 1.5m"
f-d - We regularly used N values for detail design. Although it was residential house foundations so consequences were not high risk.
RE: Correlation between SPT and Clay Properties
RE: Correlation between SPT and Clay Properties
RE: Correlation between SPT and Clay Properties
RE: Correlation between SPT and Clay Properties
RE: Correlation between SPT and Clay Properties
RE: Correlation between SPT and Clay Properties
Dik
RE: Correlation between SPT and Clay Properties
UCS on an SPT? Sure, that'll return some index value, that may be useful in correlation? I liken that to a more difficult process then using a pocket penetrometer. You also get unit charges for an UCS, which you would not get if the drilling geologist logged the holes with a pocket penetrometer in hand.
I don't have any context on residential geotechnical engineering - well other than aftermath lawsuits. . .
f-d
ípapß gordo ainÆt no madre flaca!