Siavash:
You don't mention how large your standpipe is. If it is large enough, we
have occasionally been able to push the stone down with a chimney cleaning
rod. These are about 10 or 15 mm in diameter, and come in threaded sections
about 0.5 m long. They are fairly stiff as they are used to push brushes up
flues to clean them, and available at most hardware stores. They are handy
to have around, we have been able to use them to sound broken extensions on
settlement platform extensions, check for depths of sand when installing
pneumatic or vw piezometers. If you are really lucky you might be able to
use some kind of adhesive on the bottom of the rods and pull the rock back
up (a variation of retrieving coins from the storm sewers). If you have
already pushed it down further this probably won't work.
As JD points out, prevention (and I would add redundancy) is sometimes the
best cure for this type of problem.
If the stone is above the water surface this might give you some ideas. I
have never tried it for this, but we use magnesium and sodium sulfate
solutions in the lab (AASHTO T 104) to duplicate the effect of freezing and
thawing on aggregate and to check its soundness. The material is repeatedly
immersed in a solution of the above (16 to 18 hours) and oven dried, with
the rehydration of the salt simulating the expansion of water in the
particles. An unsound material will suffer size degradation, simulating the
effects of weathering in an accelerated way. You might be able to
accomplish something like this that would be able to break up the particle.
You would have to figure out some way to dry the particle (really tough if
its plastic unless you have lots of time - could you direct a hot gas down
the tube, like vehicle exhaust or something?), and you would have to decide
whether you could accept the potential contamination of the groundwater by
the solutions.
It may be just as effective to simply replace it, rather than go to all this
bother.
Good luck, and regards,
Mike
Michael R. Bleakney, P. Eng.
Geotechnical Engineer
New Brunswick Department of Transportation
Design Branch
PO Box 6000
Fredericton, NB
E3B 5H1
Canada
Phone: (506)453-2674
Fax: (506)457-6714
E-mail: [log in to unmask]
-----Original Message-----
From: Siavash Ghabezloo [mailto:[log in to unmask]]
Sent: Sunday, February 18, 2001 1:16 AM
To: [log in to unmask]
Subject: Plugged standpipe piezometer
Hi
What we can do if a standpipe piezometer is plugged with an external
material such as a small piece of stone and probe can not reach the
water level?
Sincerely
Siavash
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