IG-032-EN version 05; 18/06/2019
21
General instructions
pfu basic range: Prefabricated concrete
enclosure, ground-level walk-in type
Installation
8.4. Preparing the ground
8.4.1. Excavation drawings
The excavation levels indicated below must be respected.
The ground must support the weight of the pfu model,
including the switchgear fitted in each case. The pressure
exerted on the ground by the pfu never exceeds 1 kg/cm
2
.
If ground bearing capacity is insufficient, it may give way
or cause loss of levelling, producing differential settlement.
Such settlement may damage the pfu structure.
There are two types of ground:
1. Ground with hardness greater than 1 kg/cm
2
:: spread
a 100 mm layer of sand over the ground and compact it
properly. Take the measures appropriate to each case to
prevent the filling sand from eroding.
2. Ground with hardness less than 1 kg/cm
2
: the base
of the pit must be covered with a layer of reinforced
concrete of at least 100 mm thick, on which a 30 to
50 mm thick layer of sand must be laid, using a level
board.
*Check with Ormazabal to define the thickness of the concrete slab.
1
Concrete slab (required if soil bearing capacity
is less than 1 kg/cm
2
)
2
Levelling sand layer
a
Excavation length
b
Excavation depth
c
Sand layer thickness
Figure 8.2.
Excavation dimensions for
pfu
(in mm)
pfu-3
pfu-4
pfu-5
pfu-7
Length (A)
4080
5260
6880
8880
Excavation depth (b)
Soil bearing capacity > 1 kg/cm
2
≈ 560
Soil bearing capacity < 1 kg/cm
2
≈ 600
Sand layer thickness (c)
Soil bearing capacity > 1 kg/cm
2
100
Soil bearing capacity < 1 kg/cm
2
30 – 50
Table 8.2.
Excavation dimensions (en mm)
When installing on a slope, please ask Ormazabal.
