Installation Manual - Future Pipe Industries

If the trench wall is of a soil type which gives insufficient support, the trench can be widened and backfilled with
a high degree of compaction (min. 90% Proctor and 70% relative density). Alternatively, support sheeting may be
left in place. The trench floor must be stabilised if it is very soft or uneven is expected.
Fig. 9.1.c.
supporting partition
backfilling material
All sharp particles must be removed from the trench floor before pipe installation. A hard uneven trench floor should
be loosened to prevent point loading. Alternatively the trench floor can be deepened by about 15 cm below the
recommended installation level and this area can be filled with sand or gravel (max. particle size 20 mm) after which
it must be compacted to a degree of compaction at least equal to the backfill material.In order to achieve sufficient
compaction of the sidefill and to have pressures in the sidefill material well distributed and transmitted to the trench
walls, the width of the trench at the crown level of the pipe should be at least:
for pipes ≤ 250 mm : W= Diameter of pipe + 30 cm
for pipes > 250 mm : W= Diameter of pipe + 50 cm
W
From approximately 30 cm above the crown of the pipe the trench may have any width. Additionally this sub-ditch will
lower the load on the pipe. The minimum depth is at least 0.5 m but this depends on pipe class, service conditions,
soil conditions and wheelload. The crown of the pipe must be installed below frost level.
Wavistrong Installation Manual
35
20 cm
0,3 x ID
first
back filling zone
~15 cm
~15 cm
excavated soil
compacting in layers
layers of 15 cm
second back filling zone
compacting in
lagen van 15 cm
bedding
foundation