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Version 1.4 May 09
5.4.1 Impermeable Material
1.
Once the cable route has been
defined, excavate a trench
( minimum 200mm deep ) along
the route from the piezometer
installation location to the intended
cable termination point. Where
compaction of backfilled material is
critical, the trench should have
sides raked at an angle of a
minimum 45 degrees.
2.
Place a minimum 100mm thick
layer of graded backfill in the base
of the trench. The backfill should
be similar to the excavated
material, graded to remove any
stones or objects that may damage
the cable. The backfill material
must have a low permeability
3.
Create a small pocket ( minimum
300mm x 300mm x 300mm ) into
which the piezometer can be
installed. Check the elevation of
the pocket to ensure that the
piezometer will be installed at the
correct level. See sketches for
level details.
4.
The piezometer can be either
placed in the pocket and
surrounded with suitable backfill
material or it can be pushed into a
pre-formed socket in the base of
the pocket.
5.
To form a socket, make or obtain a
‘mandrel’. This should be the
same diameter as the piezometer
and the socket is generally formed
so that the whole piezometer body
can slide into it.
6.
Place a 100mm layer of graded
backfill in the base of the pocket.
7.
Having prepared the piezometer for installation and recorded its site Zero
Reading ( see Section 5.1 ), bring it to site for installation in a water filled
(Continued on page 30)
Piezometer in a pocket in an impervious material
Forming hole for Piezometer in impervious material
Piezometer pushed into an impervious material
