Geotech PVT PIEZOMETER, Руководство пользователя

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GEOTECH PVT DIRECT PUSH PIEZOMETER Manual 2015-11-11
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Installation of the piezometer
Pre-drilling 3.4
If the first meters consist of dry crust with clay or silt, pre-drilling is recommended. Depending on soil con-
ditions and local quality requirements for pore pressure measurements, pre-drilling may need to be car-
ried out all the way down to the ground water table. If possible, keep the hole filled with water.
If the first meters consist of fillings, pre-drilling is recommendable through the whole filling. If the soil
seems to collapse into the hole it should be stabilized with a casing pipe or a fluid, e.g. bentonite. If cas-
ing is being used, it should be filled with water.
Should the ground be frozen, pre-drilling is always to be carried out. If the piezometer is pressed through
frozen soil, a negative pressure might occur, sucking the water out of the filter. In worst case the water
inside the piezometer could freeze and crack the sensor membrane.
Pre-drilling should always be carried out through frozen ground. Negative pore pressure could
affect de-airing. The sensor membrane might crack if the water inside the piezometer freezes.
4 Installation of the piezometer
Pushing down 4.1
The piezometer should be pushed down through the soil with a constant speed of max. 2 cm/sec – in
some soils you have to push even slower. To prevent overloading of the sensor membrane, it is recom-
mended to connect the read-out instrument and check the pressure regularly during the installation. The
pressure may never exceed the pressure range with more than 75% (valid for standard equipment). Low-
er limits may apply for piezometers with special range.
Protect the cable from tangling and from high pull forces. Make sure that there are no sharp edges that
may damage the cable. A damaged cable could make the piezometer unusable.
Push down the piezometer slowly and monitor the pressure during installation – the pressure may
never exceed the pressure range with more than 75% (valid for standard equipment). Lower limits
may apply for piezometers with special range.
Push down the piezometer with constant speed. Any kind of hammering will permanently damage
the sensitive ceramic membrane of the pressure sensor.
Protect the cable from tangling and from high pull forces. Make sure that no sharp edges damage
the cable. A damaged cable could make the piezometer unusable.