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Pneumatic Piezometer
The pneumatic piezometer is mechanically simple, inexpensive, reliable and robust. It avoids many of the problems associated with electrical instrumentation. Elevation differences between the installed tip and the reading point are of no direct significance; readings are of the pressure at the tip and no further arithmetic reductions are necessary. The system is capable of operating over relatively long lengths of connecting tubing although the reading cycle becomes progressively slower as the distance increases. Installations are possible in horizontal and upward vertical boreholes.
The instrument is designed to operate in saturated soils but will record short term negative pressures when fitted with a high air entry filter. However, because there is no facility for de-airing of the tip, this diaphragm type of piezometer is unsuitable for measuring long term negative pressures in partially saturated soils. The small volume change resulting from the diaphragm deflection during the reading process can influence measurements when the tip is installed within a highly impermeable material.
Placed in boreholes or embedded in fill materials the Pneumatic Piezometer is a low cost instrument used for the measurement and control of water pressures in soil and rock, including:
- Stability investigations of natural and cut slopes
- Control of permeability testing, de-watering and drainage
- Monitoring water table elevation
- Construction control and stability monitoring of tunnels and other underground works
- Stability monitoring of foundations, embankments and dams
- Short response time even in low permeability soils such as clay
- Excellent stability
- High and low air entry filters available
- Simple, accurate and reliable design with over 50 years of use worldwide