The society keeps building more ambitious projects. With higher skyscrapers,
longer bridges and larger dams, the use of monitoring becomes a necessity. The
constructions are exposed to many dangers, including seismic activities,
structural deformation and corrosive weather.
This application note develops two different cases:
Slope indicator probes in boreholes
Structural inclinometers fixed to critical spots
Explanation of the System
Slope Indicator Probe
Geophysical monitoring analyses the soil’s displacement in order to predict
catastrophic landslides and similar disasters. Boreholes are drilled along the
slope of a mountain, so that critical areas are identified. The probes with
embeddedinclinometers are disposed
as shown below.
Figure
1: A vertical slope inclinometer
Structural Inclinometer
A first possibility involves a sensor fastened to a building’s foundations in
order to detect the effects of collapsing fields. Another solution is to install
beams with embedded inclinometers vertically or horizontally to buildings.
Figure
2: The types of applications in urban survey
Environmental Analysis
Slope Indicator Probe
The inclinometers located in boreholes are required to provide accurate readings
during a long period of time. They also have to withstand very humid
environments. One to two sensors per probes are sufficient to get sufficient
data. The inclinometer wake up every hour to make a measurement.
Structural Inclinometer
The sensors need to be extremely accurate as the weight of the building is
massive: even a microscopic variation of angle may affect the entire structure.
Depending on the situation, the temperature variation has to be often
considered.
Performance Required
Slope Indicator Probe and Structural Inclinometer
Very low resolution < ±0.002°
Accuracy < 0.05° after compensation
ΔT = 5°C for slope indication
ΔT = 40°C for structural inclinometer
Figure
3: The arch dam at Emosson needs precise monitoring
The MEMS Potential
Slope Indicator Probe
Servo-accelerometers measure inclination with high precision, despite their
power consumption, large dimensions and expensive price. Today, the small size
and improvements in the performance ofMEMS
accelerometersmake them more
suitable for this application. An important advantage is the autonomy of these
sensors, as they need very low current to operate.
Structural Inclinometer
The MEMS capacitive sensors offer a simple, yet efficient solution for long-term
structural monitoring. Nowadays, their technology, portability and accuracy
satisfy the requirements for civil surveys.
