2. The simplicity of laying pipes made fronr- HDPE
1. Trench
The trench should be nanow, but not less than 40 cm
(16 inches) wide and should be checked for depth and slope'
The bottom of
trench must be even and stonefree.
2. Bedding
ln normal soil the bedding should be of sand or gravel and
r'
15
cm (6 inches) thick. Stones in the graUel:must not be bigger
than 20 mm. (415 inches). It is not necessary to compact the
bedding.
3. Bottom supporting
When pipe is laid clearances are allowed for sockets and
flanges so that the pipe is supported along its whole iength.
The bottom supporting is compacted as shown in the diagram.
It is important that the supporting is finn and even along whole
length of pipe, otherwse the pipe could be darnaged. lf more
than one pipe is being iaid in the trench the initial backfill for
the lower pipes must be compacted 6efore the next layer of
pipes is laid.Check the pipe for slope and alignment.
3. ww t#,j:-,
C
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4-lnitial_ Bagkfill
The initial backfill should be made in 10 cm (4 inches) thick
layers using sand or gravel and compacted as illustrated in the
diagram. lf a machine is used for compacting it should be light
and easy to handle and care should be taken that the machine
does not contact the top of the pipe.Compact to a 90% Proctor
density.
lt is this initial backfill that supports the pipe
and
protects if from deformation so that compacting must be carried
out carefully by tamping on each side of the pipe altemately. lt
is important that gravel size should.not be greater than 20 mm.
(4/5 inches)diameter.
5, Prp.tecjive
.. Use
Fl|Jir.rg
the same
s'
described'for the initial backfill.
,'B-
It is essential that thbre are no large stones in this fill as they
can cause point stresses on the pipe and damage it. protective
filling should be 30 cm. (t foot) thick and tamping with a heavy
machine on top of the pipe should be avoided. lf ground water
flows into the trench during ihis operation increase the speed of
filling or the or the pipe wilt ftoat
6.
Final. Backfill
complete the filling of the temch with the excavated materiar
evenly distributing the stones through out ihe fill. compact to
minimum
of g0% Proclor density. Foilow the
building instructions. The pipelaid will need
maintenance.
recommended
a
minimum of
Li;-
