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Vibrating Wire Piezometer Applications Typical applications for the VW piezo- meter are: • Monitoring pore water pressures to determine safe rates of fill or exca- vation. • Monitoring pore water pressures to determine slope stability. • 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. • Monitoring pore pressures to check containment systems at land fills VW Piezometer(top)and VW Push-In Piezometer(bottom). and tailings dams. Operation Installation Overview Advantages The VW piezometer converts water Grout-In Method: The piezometer is Groutable: The VW piezometer can pressure to a frequency signal via a lowered to the specified depth,and be installed without a sand filter or diaphragm,a tensioned steel wire, the borehole is simply backfilled with bentonite seal.This greatly simplifies and an electromagnetic coil. a bentonite-cement grout. Read same-hole installation of multiple The piezometer is designed so that a more about this method at Slope piezometers or piezometers with change in pressure on the diaphragm Indicator's website:www.slopeindi- inclinometer casing. causes a change in tension of the cator.com. High Resolution: VW piezometers wire.An electro-magnetic coil is used Sand Filter Method: The borehole is provide a resolution of 0.025% of full to excite the wire,which then flushed with water or biodegradable scale. vibrates at its natural frequency.The drilling mud.A sand filter is placed vibration of the wire in the proximity High Accuracy: Slope Indicator's P y around the piezometer at the speci- automated, precision calibration sys- of the coil generates a frequency sig- fied depth.A bentonite plug is tem ensures that VW piezometers nal that is transmitted to the readout formed at the top of the sand filter. meet or exceed specifications. device. Then the remainder of the borehole is The readout or data logger stores the filled with a bentonite-cement grout. Rapid Response: VW piezometers reading in Hz.Calibration factors are push-In: The piezometer is pushed respond very quickly to small changes in pore-water pressure, then applied to the reading to arrive into soft cohesive soil at the bottom whether they are grouted in,pushed at a pressure in engineering units. of a borehole.The piezometer must into cohesive soils,or embedded in a be monitored to ensure that it is not sand filter zone. overpressured as it is pushed in. Reliable Signal Transmission: With Embankments: The piezometer is properly shielded cable, signals from embedded in sand and then covered the VW piezometer can be transmit- with hand-compacted select fill.Sig- ted long distances. nal cables are routed through trenches and covered with com- pacted fill. Bentonite water stops are placed at appropriate locations.