Hello:
I happen to study into jet grouting of marine clays for my Masters of
Engineering. There was somebody else studying for deep cement mixed marine
clays. By the way, there is much info in the following:
"Grouting and Deep Mixing", Second International Conference on Ground
Improvement Geosystems, Tokyo 1996.
"Grouting in the Ground", Proceedings of Conference Orgnaised by ICE, London
1992.
Anyway, in my thesis I covered something I referred to as "workable limit"
of cemented clays (my supervisor is writing the paper to ASCE and it is
apparently taking a long time to be reviewed). It seems that when a little
bit of cement (say 5% cement by weight of solids) is added to clay slurry,
it becomes very viscous and has a higher liquid limit than clay itself. On
addition of more cement, the liquid limit than drops. The turning point of
the pick up to the drop of the liquid limit and "bleeding limit" (something
I dreamed up) was at about 8% cement to total soilds wt. I think it is a
collodial particle interaction thingy that I do not pretend to understand
very well.
I think it is important to understand the viscosity limits of the mix you
are targetting. It may be useful to check with simple tests such as liquid
limit and plastic limits to see the constituent content (water, clay solids,
cement) you are looking at.
I believe in jet grouting, the mix should be wetter than liquid limit. In
DCM (deep cement mixing, wet or dry), it would be drier. But by being not a
"liquid", compaction is required. If you look at the many literature in lab
based tests on DCM mixes, it always involves some kind of compaction. Even
in the DCM process itself, the blades actually sort of compacts the soil on
withdrawal. How to relate the compaction effort to lab means of compaction
may be another problem.
Anyway, for my research in jet grouting which involves mixes of wetter than
liquid limit, the strength of the samples with cement content less than the
"turning point" (approx 8% cement / total solids by weight), the samples
were basically jelly (almost 0 strength) which shrinks to half its size when
dried up.
I suggest that you conduct say 2 to 3 ranges of compaction effort for the
same mix.
Although lab tests may not be comparable to actual field results, it is
important to have a basis for estimation based on controlled results. A bad
guess based on facts is better than a blind shot in the dark. So, do not be
deterred by the difference in lab and field results.
If you want any more info, please e-mail me. If I can get hold of the DCM
guy who did his Masters with me, I'll get him to write to you.
Yah, nearly forgot. Do not be tempted to dry the clay (if you ever use
actual soil), the properties changes very much.
Hope I have been of help.
Lee Yeong
BBR Ground Engineering
Singapore
>
>Deal all
>I am studying on the behaviour of cement-treated soil and modeling work of
>bonded soil, especially cement-treated clay. For the lab test condition, I
>assumed that deep mixing works is going in the marine clay.
> >>I did the lab tests to get the mechanical properties of cement treated
>soil, for these I applied pure kaolin and Portland cement with water
>content (70, 100%) and cement ratio (2, 5, 10%). I used under water curing
>instead of humid curing method, but almost all curing method done by other
>authors are humid curing method. I found that sample preparation was very
>difficult, because the mixing soil cement sample change to the stick state
>if the cement ratio higher than 10%. Below 10% cement ratio, the effect of
>cement as a stabilizing agent was not favorable.
>
>My questions are
>
>1.Sample preparation method for soil cement mixing sample, especially clay
>+ cement.
>2.What is difference between under water curing and humid curing?
>3.What is the real cement ratio usually applied in the real fieldwork?
>
>Please let me know if you have any other ideas and have experience,
>
>Good Luck
>
>
>
>==================================================
>Kyuhwan Lee
>
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