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| SPIGOT & SOCKET PIPES - RECOMMENDED TRENCH WIDTH AND BEDDING PIPES |
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When laying pipes, to attain its full potential as a load
bearing structure, trench width, proper bedding and
backfilling are equally as important as the actual pipe
strength. In fact, almost 50% of the completed structure
is attributed to proper design and good workmanship.
Any increase in trench width above that specified will
increase the load on the pipe and a narrower trench
may impede the proper placing and consolidation of
bedding.
The trench should be dug so that the line, gradient and
dimensions are as specifications or as agreed with site
engineer.
The bedding is intended to level out any irregularities in
the formation and ensure uniform support along the
barrell of pipe.
Click here to view diagram
The selections of bedding material and bedding class is
influenced by many factors which include the nature of
the ground, the loads acting on pipeline, availability of a
particular type of bedding material. The ideal is crushed
rock or gravel that is compatible and provides stable
embedment.
For more details on bedding and pipe specifications see
C.P.A. (Concrete Pipe Association) publications.
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Typical Bedding Detail
Click here to view larger diagram
It is recommended that were pipes have to be airtested,
it should be done every fourth pipe and prior to back
filling.
Cover to pipes (H) laid in fields for agricultural purposes
only = 600mm.
However, it is advisable that pipes laid under roads
carrying traffic or grass verges adjacent to such roads,
should have a minimum 1200mm cover.
Never drive across a pipeline with minimum cover
unless at prepared crossings.
Ground water should be kept below the bottom of
trench by use of temporary drains and not allowed to
rise before backfilling is complete.
Special care should be taken with the bedding material
immediately surrounding the pipes to minimise the
possibility of lumps or others coming into direct contact
with pipes thus causing point loading.
Never bulldose backfill directly into trench.
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