Application
A real-time alternative to the traversing probe type of inclinometer, the in-place inclinometer employs a fixed string of sensors and does not require an on-site operator. It is ideal for data logging and real-time, remote monitoring for critical applications such as construction control. Typical applications include:
- Monitoring landslide areas above dams, highways, and railroads to provide early warning of slope failure.
- Monitoring ground movements induced by tunnel construction and excavation.
- Monitoring deformations of embankments and retaining walls
Operation
The in-place inclinometer system consists of inclinometer casing and a string of electrolytic inclinometer sensors. The inclinometer casing is installed in a vertical borehole that passes through a suspected zone of movement. The string of sensors is positioned inside the casing to span the zone of movement.
The sensors measure the inclination of the casing. Changes in the inclination readings indicate that the casing has been displaced by ground movement. The amount of displacement is calculated by finding the difference between the current inclination reading and the initial reading and then converting the result to a lateral distance.
In most applications, sensors are connected to a data acquisition system that continuously monitors movements and can trigger an alarm when it detects a change, or rate of change, that exceeds a preset value.
Advantages
Single Cable Installation: The multiplexed version of the EL IPI installs with just one cable. Although multiplexed sensors are more expensive, their higher cost is partially offset by easier installation and wiring, and savings on signal cable and external multiplexers.
High Resolution: The ceramic EL sensor has a range of +/- 10 degrees and a resolution of 9 arc seconds (0.04 mm/m) with a CR10X. Increased resolution is possible with a higher resolution readout device.
Ideal for Critical Applications: In-place inclinometers are easily connected to data acquisition systems with on-site alarms and automatic dialers. Built-in signal conditioning ensures compatibility with most data loggers.
Lower Cost: EL IPI systems cost significantly less than comparable servo-accelerometer systems.
Wheels: Wheeled sensors can be removed to allow verification checks with a traversing probe or when sensors are needed at a different site.
Rigid Gauge Tubing: Inclinometer calculations assume straight-line segments for sensor gauge lengths. Rigid gauge tubing satisfies this assumption. Rigid gauge tubing also provides reliable performance in soft ground, where abrupt changes in profile may occur at a shear zone.
