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Vibrating Wire Piezometers �} Applications VW piezometers are used to monitor pore-water pressure.They can also be used to monitor water levels. Typical applications include: • Monitoring pore water pressures to determine safe rates of fill or exca- vation. • Monitoring pore water pressures to determine slope stability. � ,G . • Monitoring the effects of dewater- ing systems used for excavations. • Monitoring the effects of ground � improvement systems such as ver- tical drains and sand drains. • Monitoring pore pressures to check the performance of earth fill dams and embankments. 4 , � • Monitoring pore pressures to check containment systems at land fills and tailings dams. • Monitoring water levels in stilling basins and weirs. VW Piezometers:Standard,Low-Pressure,and Push-in(bottom) Operation The VW piezometer converts water Installation Overview Advantages pressure to a frequency signal via a Grout-In Method: The piezometer is Groutable: The VW piezometer can diaphragm, a tensioned steel wire, lowered to the specified depth, and be installed without a sand filter and an electromagnetic coil. then the borehole is backfilled with a zone.This greatly simplifies the The piezometer is designed so that a bentonite-cement grout. installation of multiple piezometers in change in pressure on the diaphragm Sand Zone Method: The piezome- the same borehole. It also provides a causes a change in tension of the ter is lowered to the specified depth. way to install piezometers with wire.An electro-magnetic coil is used A sand filter zone is formed around inclinometer casing. to excite the wire, which then the piezometer.A bentonite plug is High Resolution: VW piezometers vibrates at its natural frequency.The placed at the top of the zone,and the provide a resolution of 0.025% of full vibration of the wire in the proximity remainder of the borehole is grouted. scale. of the coil generates a frequency sig- Embankment Method: The piezo- High Accuracy: Slope Indicator's nal that is transmitted to the readout meter is embedded in sand or grout automated, precision calibration device. and covered with hand-compacted system ensures that these sensors The readout or data logger stores the fill.Signal cables are routed through meet or exceed specifications. f reading in Hz. Calibration factors are trenches with bentonite water stops. Rapid Response: VW piezometers then applied to the reading to arrive push-In Method: The push-in pie- respond very quickly to small at a pressure in engineering units. zometer can be pushed a short dis- changes in pore-water pressure, tance into soft soil at the bottom of a whether they are grouted in, pushed borehole.The piezometer must be into cohesive soils,or embedded in a monitored to ensure that it is not sand filter zone. overpressured as it is pushed in. Reliable Signal Transmission: With Weirs: The piezometer is fixed to the properly shielded cable,signals from wall of the weir. In this application, the VW piezometer can be transmit- barometric pressure should also be ted long distances. monitored.