Installing the 3TB in a borehole
The following photographs show the steps involved in backfilling with sand:
4.2.1 Procedure
To install a sensor at the bottom of a borehole of known depth using sand backfilling:
1. Measure or calculate the physical volume of the unit which is to be installed
in the borehole. (The volume of a cylinder is given by v = πr2h.) Also measure
the internal diameter of the borehole.
2. Measure and pour in a sufficient quantity of sand to fill the borehole to a
depth of around 300 mm.
3. Connect the signal
cable to the connector
on top of the sensor.
Ensure that the “O”-
rings inside the
housing are clean and
well-greased. If
necessary, apply a coat
of extra silicon grease
to the 'O'-rings: Dow
Corning Molykote 111 is
suitable. Tighten the
knurled connector nut
to its end stop. It may
be necessary to wiggle
the connector several
26
Issue G - November 2019
