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4.2.2 Uplift prevention
•
The pit design ensures that the pit is protected against uplift if
installed correctly (excluded D 800 x 1000 and D 1200 x
1500). Requirements for uplift prevention depend on the
geotechnical conditions. They must be determined by the
engineer or contractor and are outside Grundfos' area of
responsibility.
The requirements below are the minimum
requirements. Observe local regulations.
The safety against uplift is determined according to Eurocode EN
1997-1 including national annex, DS/EN 1997-1 DK NA:2015.
The most unfavourable ground water conditions for the pit is
when the ground water table is located at terrain level. This
situation creates the highest hydrostatic water pressure at the
bottom of the pit, and causes the highest reduction in soil weight
for the stabilising soil volume.
The sand volume resting on the pit's shoulder is a stabilising
force. The sand volume is determined as a cone with hollow core
as illustrated in fig. 7.
The inclination of the cone is illustrated 1:n. The inclination n can
be determined based on the friction angle for the design. The
characteristic friction angle for sand with a unit weight of 19 kN/
3
m
, compacted to 97 % standard proctor, is estimated to 37
degrees. The design friction angle is 32 degrees which
corresponds to an inclination of n = 1.6.
Fig. 7
Stabilising sand volume
4.3 Installing the valve chamber
When installing the valve chamber, follow the same instructions
as for installation of the pit. See section
The valve chamber is only to be installed for PS.R.17
pits.
Isolating valves
Non-return valves
Fig. 8
Valve chamber
4. Installing the
product.
7
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