Soil Instrumentation

Piezometer

Operating Principle

The VW piezometer converts water pressure to a frequency signal via a diaphragm, a tensioned steel wire, and an electromagnetic coil. The piezometer is designed so that a change in pressure on the diaphragm causes a change in tension of the wire. An electro-magnetic coil is used to excite the wire, which then vibrates at its natural frequency. The vibration of the wire in the proximity of the coil generates a frequency signal that is transmitted to the readout device.

Applications
The VW piezometer is used to monitor pore-water pressure, e.g, Monitoring

to determine safe rates of fill or excavation.
to determine slope stability.
the effects of dewatering systems used for excavations.
the effects of ground improvement systems such as vertical drains and sand drains.
pore pressures to check the performance of earth fill dams and embankments.
pore pressures to check containment systems at land fills and tailings dams.

Advantages

Data reading is simple and reliable yet to avoid human errors at jobsite.
Experice engineer (Berpengalaman)
Quick and good response time even in soils with low permeability.
Less expensive than other types of diaphragm piezometers.
Reading station is remote from work area and does not interfere with construction activity.
Not damaged by freezing.

The READOUT or data logger stores the reading in Hz.
Calibration factors are then applied to the reading to arrive at a pressure in engineering units.
Some readout devices display a simple frequency reading.
Other readouts, convert the frequency reading to units of pressure or water head.

Inclininometer

Inclinometer designed to measure lateral movement of earthworks or structures.

The reading of Inclinometer data provides:

quantitative data on magnitude of inclination of foundations and its variations with time.
the pattern of deformation
zones of potential danger
construction control measures

Inclinometer Probe
The wheeled inclinometer probe tracks the longitudinal grooves in the casing. It contains two force-balanced servo-accelerometers.

One accelerometer measures tilt in the plane of the inclinometer wheels. This plane is known as the A axis. The other accelerometer measures tilt in a plane perpendicular to that of the wheels. This plane is known as the B axis. Tilt readings are typically obtained at certain intervals
(narasi belum ada. Foto sudah ada)
as the probe is drawn from the bottom to the top of the casing.