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Version 1.4 May 09
2.
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.
3. Where
the
excavation
is
in a granular material, place a layer of Geotextile
material in the base and up the wall of the excavation, then a 100mm layer of
graded sand in the base of the trench and pocket.
4.
Having prepared the piezometer for installation and recorded its site Zero
Reading ( see Section 5.1 ), bring it to site for installation. Check the function of
the piezometer using a portable readout.
5.
Carefully remove the piezometer
from the water filled container and
place it in the sand pocket as
shown.
6.
Coil the cable in the pocket, to
form a loop as shown. This helps
to reduce the risk of cable damage
due to excessive settlement or
stretching.
7.
Lay a section of the cable into the
trench and backfill the pocket and
trench with stone free sand as
shown in the above sketch. It may
help to pour some water over the
sand to assist with compaction.
8.
Complete the cable laying operation,
snaking the cable in the trench only where specified, and backfill the trench with
sand. ( Laying the cable in a ‘zig - zag’ or ’snaking’ pattern is sometimes
specified with the intention of reducing the risk of cable breaks due to stretching.
The preferred solution is to use a good quality cable without steel armouring,
laid in a straight line ).
9.
Before resuming any further filling operations, check the function of the
piezometer using a portable readout.
(Continued from page 27)
Piezometer in a pot in a permeable material
