Re: neutron probe aluminium tube

[Jim Prochaska <jnmtexas@startel.net>]

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Dear Magdeline,

Bentonite alone may not seal the air gap.  Normally you must swell it with
water.  If your soils are heavy clays that tend to swell when wetted, then the
problem will correct itself if wetted.  Unfortunately you have to add water to a
system that you really didn't want to be different than the surrounding soil.
If time is not an issue, then the surrounding soil and soil around the tube will
equilibrate after adding water, but if you need good, accurate data now, I would
recommend that you drill new holes.  I think that many of us have been in this
situation from time to time.

Jim Prochaska, PE
JNM Technologies, Inc.
jnmtexas@startel.net



owner-sowacs@aqua.ccwr.ac.za wrote:

> Dear subscribers,
>
> I have a slight dilemma. I have recently installed a neutron probe aluminium
> access tube and the hole drilled for installation is slightly larger than
> the tube (only about < 5mm diameter). Should I leave the small air gap as it
> is or fill it with bentonite? Which will affect my readings more?
>
> Thanks
>
> ****************************************************************
>
> Magdeline Pokar,                Tel: 0113-2335231 (O)
> School of Earth Sciences,            0113-2343795 (H)
> University of Leeds,            Fax: 0113-2335259
> Woodhouse Lane,                 email: M.Pokar@earth.leeds.ac.uk
> Leeds, West Yorkshire,
> LS2 9JT. UK


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