Piezometers
Introduction  |  Standpipe Piezometer |  Pneumatic Piezometer |  Vibrating Wire Piezometer

Applications

Typical applications for piezometers are:

• Monitoring pore water pressures to determine safe rates of fill or excavation.
• Monitoring pore water pressures to evaluate slope stability.
• Monitoring dewatering systems used for excavations.
• Monitoring ground improvement systems, such as vertical drains and sand drains.
• Monitoring pore pressures to check the performance of earthfill dams and embankments.
• Monitoring pore pressures to check containment systems at landfills and tailings dams.

Types of Piezometers

Standpipe Piezometers
The standpipe piezometer, which is installed in a borehole, consists of a filter tip joined to a riser pipe. Readings are obtained with a water level indicator.

Advantages: Simple, reliable inexpensive, not electrical, no calibrated components.

Limitations: Accuracy depends on skill of operator; reading requires a man on site; remote reading not possible; slower to show changes in pore-water pressure.

Pneumatic Piezometers
The pneumatic piezometer consists of a pneumatic pressure transducer and pneumatic tubing. It can be installed in a borehole, embedded in fill, or suspended in a standpipe. Readings are obtained with a pneumatic indicator.

Advantages: Reliable, remote reading possible, not electrical, indicator can be calibrated at any time.

Limitations: Accuracy depends on skill of operator; difficult and expensive to automate, so reading requires man on site; reading time increases with length of tubing; pneumatic tubing can be blocked by condensation if not frequently charged with dry nitrogen gas.

Vibrating Wire Piezometers
The vibrating wire piezometer consists of a vibrating wire pressure transducer and signal cable. It can be installed in a borehole, embedded in fill, or suspended in a standpipe. Readings are obtained with a portable readout or a data logger.

Advantages: Easy to read, very accurate; good response time in all soils; easy to automate; reliable remote readings.

Limitations: Must be protected from electrical transients; must compensate for barometric pressure when used in wells that are open to atmosphere.