Super Soft Clay
Super Soft Clay
(OP)
What is Super Soft Clay? can any one say about characteristic of this kind of soil? is this soil liquefy?
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RE: Super Soft Clay
RE: Super Soft Clay
RE: Super Soft Clay
Second, generally speaking clays don't liquefy. This doesn't mean that there will not be displacement due to a seismic event. Again, the geotechnical engineer for the project can help with that analysis.
Lastly, 50 to 70 kPa is not super soft, not even soft. This equates to about 1,000 to 1,500 psf which we consider stiff clay. Th fact that your moisture content is above the liquid limit, but your strength is pretty good indicates that the material is sensitive to disturbance. Again, you need to discuss your project and the impact of this material with your project geotechnical engineer.
Mike Lambert
RE: Super Soft Clay
according to A. Fakher, Lecturer, Department of Civil Engineering, Tehran University, Iran, Clay having a very high water content behaves neither like a liquid nor like a solid, it has very little shear strength but some times Shear strength may varie from <0.1 KPa to 1000 of KPa, which is case sensative and can be termed a super soft clay. clay is neither a liquid nor a solid; it is a material with characteristics bordering between the two. It may be defined as a soil with no practical bearing capacity, often displaying a fluid-like consistency and behaviour.
Similarly, you should be clear that there were many cases, Flow liquefaction occured in Clay having Plasticity Index greater than 20, having Liquid Limit > 50.
I think, You may not gone through recent study over liquefaction, please once search liquefaction on clayey soil and reply me.
RE: Super Soft Clay
I don't recall the index properties of the Bootlegger Cove Clay, but your soil sounds similar. Be careful!
RE: Super Soft Clay
Terminology:
"Sand-like" (or cohesionless) refers to soils that behave like
sands in monotonic and cyclic undrained loading. Onset of
strength loss and large strains is "liquefaction."
"Clay-like" (or cohesive) refers to soils that behave like clays
in monotonic and cyclic undrained loading. Onset of strength
loss and large strains is "cyclic softening."
RE: Super Soft Clay
As I indicated, "generally" speaking clays don't liquify. Strain softening, yes, but that is not liquifaction.
Again, the strengths are are reporting are not soft. Clay with strengths that you report would be fine supporting fairly light structures under most conditions, therefore it does have a practical bearing capacity.
Could your clay loose strength due to remolding in an earthquake due to sentivity, maybe. But an online form is not the place to be getting advice if you have that kind of problem. You need people experienced in the local geology and who understand the seismic risk.
Mike Lambert
RE: Super Soft Clay
Unless you have some extremely high column loads or a huge mat foundation with high loads, I wouldn't worry too much about your clay layer.
RE: Super Soft Clay
RE: Super Soft Clay
RE: Super Soft Clay
From AGMU 10.1
Low plasticity silts and clays may experience pore-water pressure increases, softening, and strength loss during earthquake shaking similar to cohesionless soils. Fine-grained soils with a plasticity index (PI) less than 12 and water content (wc) to liquid limit (LL) ratio greater than 0.85 are considered potentially liquefiable and require liquefaction analysis. While PI is regularly
investigated for pavement subgrades, it has rarely been considered in the past for structure soil borings. However, in order to investigate liquefaction susceptibility of fine-grained soils, the plasticity of such soils should be examined when conducting structure soil borings. Drillers should inspect and describe the plasticity of fine-grained soil samples. Low plasticity finegrained
soils, particularly loams and silty loams, should be retained for the Atterberg Limit testing with the results indicated on the soil boring log.
What happen if my soil is clayey silt? is that liquefy now? if my PGH is arround 300 gal?
RE: Super Soft Clay
You seem to have all the information and answers, so why are you posting the question here? We are not going to run the analysis for you.
As has been pointed out, strength loss and movement of the clay or any soil are possible due to a seismic evenet whether the material liquifies or not.
Mike Lambert
RE: Super Soft Clay
RE: Super Soft Clay
Have you done any crosshole shear-wave testing to derive the low-strain shear modulus?
f-d
¡papá gordo ain’t no madre flaca!
RE: Super Soft Clay
I have six different borehole, i have some physical tests, i have NMC, LL, PL, PI, Unconfined compression data, Triaxial data, Consolidation data, Seive Data with SPT value, but dont have any dynamic parameter like shear wave...due to limitation of technology and cost available on my country i have no any other option for deatail field works and further analysis...neither we have any software nor standards or books. We are still following old books and mannuals i.e. from late 80's.
So i need modern methodology, codal provison and findings from you guys.
We are still using cast insitu bored pile, no driven pile nor precast pile within my country.
Even bored pile is uncased....
So whats ur suggestion for me, to resist 2000 KN of load with single cast insitu bore pile for Road Flyover....
Soil Parameter,
Layer 1 SPT Nfield-6, from ground to 11 m, silty sand, Phi=31
Layer 2 SPT Nfield-50 average, 11m to 20 m, Coarse sand, Phi 34
Layer 3 SPT Nfield-6 average, 20 m to 100 m, clayey silt, c=50Kpa, LL=60, NMC=70, PI=15, cc=0.4, clay=9%, silt=85%, organic matter=6%
For liquefaction analysis PGA=300 gal,
If any one have any idea please advice me depth of required pile, if 1500 mm dia pile will preferred?
RE: Super Soft Clay
I have always been under the impression that below 40 ft (13 or so meters), liquifaction is not an issue. Too much confining pressure.
f-d
¡papá gordo ain’t no madre flaca!
RE: Super Soft Clay
RE: Super Soft Clay
f-d
¡papá gordo ain’t no madre flaca!
RE: Super Soft Clay
RE: Super Soft Clay
RE: Super Soft Clay
http://cee.engr.ucdavis.edu/faculty/boulanger/PDFs...
That's probably the best source on clay with cyclic loading available at present. If you have access to the ASCE Jnl of Geotechnical Engrg., look for a paper by Tim Stark and Ivan Contreras on the 4th Avenue slide in Anchorage, Alaska, in the same 1964 earthquake as the Turnagain slide that aeoliantexan mentioned, maybe 10 years ago. It may be referenced in that report I gave you the link for.
Interesting that the water content is greater than LL at such a great depth, with N ~ 8.
aeoliantexan - Are you in the town of Aeolian (Eolian?)? Must be windy there.
Regards,
DRG
RE: Super Soft Clay