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Fig. 11 Lifting the pit (PUST17)
Warning
Observe local regulations.
9. Installation
4
Fig. 12 Schematic installation drawing
Pos.
Description
1
Foundation layer
2
Bedding layer
3
Backfill, compacted in layers of maximum 30 cm
Distance of 50 cm from cover where heavy traffic
4
loads must not occur
The location of the pit must be selected so that
its establishment does not damage other
Caution
constructions. Conversely, these must not
damage the buried pit.
Foundation layer
•
The bottom of the pit must have a foundation layer if soil
analyses and information about pit load show that the bottom
is not capable of bearing. The bedding layer on which the pit is
placed is not regarded as a foundation layer.
•
The foundation layer can be made after the excavation by
laying a stable layer of suitable gravel or similar material and
compacting it in layers of maximum 30 cm (corresponding to
approx. 20 cm after compaction). Such a foundation layer is
also required if the excavation has become too deep by
mistake.
10
4
3
2
1
Bedding layer
•
The material for the bedding layer must be compactable and
composed so that neither its properties nor compaction will
cause damage to the pit.
•
Grains larger than 16 mm must not be present.
•
The content of grains between 8 and 16 mm must not exceed
10 %.
•
The material must not be frozen.
•
Sharp flint etc. must not be present.
•
The bedding layer must usually have a thickness of 10 cm.
If the bottom of the excavation meets these requirements, a
bedding layer is not required.
Backfill
•
The backfill must provide sufficient support of the pit on all
sides and ensure that the load can be transferred without
detrimental point impacts or similar impacts.
•
The backfill must meet the same requirements as those for the
bedding layer.
•
The backfilling must be carried out so that the pit is not
damaged or deformed.
•
The backfill must be compacted in layers of maximum 30 cm
(corresponding to approx. 20 cm after compaction).
Warning
Before the pit is lowered into position, various
connections must be retightened, as they may
have become loose during the transport.
Check the pit for external damage before
lowering it into position. When the pit has been
Note
installed, Grundfos cannot be held responsible
for possible damage.
Place the pit on the bedding layer.
Check that the pit is vertical.
Groundwater must not rise above the bedding layer until the
backfilling has been completed.
Compact the bedding layer under the inlet and
discharge pipes properly so that they are not
Note
exposed to downward loads when the backfill is
compacted. See fig. 13.
Fig. 13 Insufficient compaction under pipes
During backfilling, the cover must be on the pit to
Note
ensure that the pit is not deformed (becomes
oval).
Fig. 14 Oval pit after compaction
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