Suggested solutions for coring in clay

[Katherine HARLE]

Thankyou very much to all who replied to my plea for help regarding coring
in clay.  There was a fairly wide range of solutions suggested, which makes
me wonder whether it would be a good idea to put together an updated booklet
or perhaps an article for QA on coring techniques for different sediment
types.  Any volunteers? Guaranteed support of the QA editor! (:

Below are the solutions suggested.
thanks
Kate


The gemco corer/drill that ANU is using and has for the sleads project is
just the thing.
Patrick De Deckker
patrick.dedeckker at anu.edu.au


there is a company based in Brisbane run by Dr Trevor Graham called
Geocoastal.
highly recommended and I shall find his email address and send it tomorow.
regards
Kriton Glenn
Kriton.Glenn at agso.gov.au


I have successfully used a vibrocorer in saltpan and mangrove sediments here
in Townsville.  I don't know what setup you have available, but we had a big
tripod setup with a winch to help extract the cores.  The dry sediments were
harder but not impossible to core.
Ingrid Ward
iakw01 at uow.edu.au

I suggest using 90mm plastic pipe with a slide hammer to go in.  Cap and
pull out with a chain block held by a tripod.  If you want more info or even
to borrow the gear and a techo to fly it contact me.  there is a photo of
the method on our web page too.
Stuart Pearson
ggsgp at cc.newcastle.edu.au

Yes, a vibrocorer with sharpened tip and a couple of hefty technicians to
lean on it would be the go.  Ideally, catch it just after it's emerged
from it's seasonal soaking.
Piers Larcombe 
piers.larcombe at jcu.edu.au


I have been taking a lot of cores lately in mangroves. I use a 3" soil auger
to trudge down through the first 50-150cm, then often a D section will take
softer materials. Or you could try a Livingstone. Advantages: cheap, and it
does the job at slight risk of contamination.
The corer you want is a hammered corer with a cam piston (basically
Livingstone in design), with a tripod and great big hoist. Steve Athens has
been taking 20m cores through clay, sand and lumps of coral in the Pacific
with one of these and swears they are unstoppable. The core piston is locked
and only released by internal wire at the start of a drive. The barrel is
aluminium and this is sacrificed as a storage for the core - so you need 40m
of pipe to go down 20m. The tube is cut open on a table saw. Steve has a
tame guy who makes these, but they are expensive. You can get details by
mailing iarii at aloha.net 
ANU will rent you a light JACRO with split tube- light is still pretty heavy
(eg 250kg) however. Discuss with Damien Kelleher.
Geoff Hope 
Geoff.Hope at coombs.anu.edu.au

We've have a mobile (6kg) tonker designed by Nigel
Cameron for the one which fortunately (!) has water in it. She can borrow it
in
Feb when she comes past here if she will ship it back. The shallow one is
good
for the ol pipe and wet tennis ball technique. If she want to control for
compaction she can measure down the pipe after every 5 cm of tonking and
measure
in segments the amount of compaction down the core.
Peter Gell 
peter.gell at adelaide.edu.au


Sounds like Dr Morris needs hammer driven samples using a Longyear rotary
rig. This method is used routinely for ground investigation in civil
engineering projects. They are referred to as U76 undisturbed samples. 
Dr. Yim 
wwsyim at hkucc.hku.hk

Damien Kelleher and I have drilled through over 40 metres (two cores) of
exactly the same dense palaeolacustrine clay at Lake Lewis. We got excellect
recovery, little to no compaction, perfect core, even though it's as tough
as old boots.

Damo used a truck-mounted Edson 360 Versdrill top drive rotary rig with
conventional hollow augers. Plus some deeper probes with solid augers from
which I took grab samples of the clay from the fetches. I don't know if Damo
will be over in WA with the rig in the near future, although he gets around
with it, and helps a lot of people out. I think JC is sending him back to
drill in New Guinea presently. Damo has also done plenty of drilling through
water. His email is: damien.kelleher at anu.edu.au
Pauline English
Pauline.English at anu.edu.au


During fieldwork for my doctorate working on coastal 
wetland sediments in southern Sicily (Central 
Mediterranean), I encountered much the same problem with 
sun-baked salt marsh and lagoonal sediments. I used two 
open d-shaped gouges, 8 and 3.5 cm diameter respectively.
I found that although the surface 30 cm was often almost 
impenetrable, fine grained sediments at depth were 
extracted without too little damage. I used the narrow 
gouge on really firm clays, just to build up an idea of the 
stratigraphy.
After my first, rather unsuccessful coring campaign in the 
summer, I went back to the same sites in the Spring, 
following winter rains, which yielded much better cores. 

I  also found that the open gouges worked OK in submerged 
settings, if (and it's a big IF) the sediment was mainly 
fine-grained sediment. The first bit of sand or shell 
accumulation and the core usually slid out under its own 
mass during retrieval.

You've probably worked all this out already, but I'd give 
the open gouges a go. I would have been stuck without them. 
The other thing was that I filed the cutting edge of the 
gouge before insertion, in clays the difference was 
surprisingly noticeable.

Hope of some use, best of luck with the coring.
Dr. Simon Turner
S.D.Turner at exeter.ac.uk


We did some coring into clay a few years back at my site at Clarence 
Lagoon in Tasmania.  We set up a tripod in about 1.5 m of water and 
bashed in a steel pipe and then used a block and tackle to extract the 
pipe.  We did have a bit of trouble with the sleeve slipping on the pipe 
during the whole process, but managed to extract about three metres of 
mostly clay.
Feli Hopf 
feli at yvh.au.com