Installing the 3ESP
hand-operated post-hole auger. To minimize surface effects, you should ensure that
the hole is at least 1 m deeper than the length of the instrument, and preferably
somewhat more.
Since the hole has no lining, it may occasionally flood. However, most soil types are
sufficiently permeable to allow water to soak away, leaving the packing material
moist.
To install a 3ESP in a post-hole:
1.
Clean the post-hole, making sure there is no loose material around the mouth
of the hole or on its base.
2.
Prepare the instrument package, making sure the inclinometer is visible, and
attach it to a winch or hoist by clamping a light steel cable to the centre of the
handle so that the package hangs vertically. Connect the signal cable to the
instrument.
3.
Add packing material to the hole to about 15 cm depth. Fine crushed rock, with
a high proportion of rock flour and fine particles, makes excellent packing
material. Alternatively, a mixture of 3 mm grade angular coarse grit with
around 30% medium grit gives good results. Moisten the packing material in
the hole and ram firm.
4.
Lower the instrument to the bottom of the hole, but without slackening the
lifting cable.
5.
Fill more packing material around the instrument for about 30 cm, moisten,
and ram firm.
6.
Use the inclinometer to check that the instrument remains within its tilt
tolerance (± 2 °).
7.
Continue filling, moistening and packing until the instrument is buried,
checking that the tilt remains within tolerance.
8.
Release the strain on the lifting cable, and allow the packing material to settle
for 24 hours.
9.
If all is well after the settling period, release the lifting tackle, coil a tail of the
lifting wire into the top of the hole and backfill almost to the surface.
10.
Ensure that the signal cable is slack, and fix it to a support at the top of the
hole.
11.
Ram a split wooden bung into the top of the hole, and cover with sandbags.
12.
Attach the signal cable to your recording equipment or breakout box. Carry out
preliminary tests using a hand-held control unit, if required.
18
Issue G - February 2016
