Introduction to Inclinometers

Applications

Inclinometers are used to monitor subsurface movements and deformations. Typical applications include:

• Monitoring slopes and landslides to detect zones of movement and establish whether movement is constant, accelerating, or responding to remedial measures.
• Monitoring diaphragm walls and sheet piles to check that deflections are within design limits, that struts and anchors are performing as expected, and that adjacent buildings are not affected by ground movements.
• Monitoring dams, dam abutments, and upstream slopes for movement during and after impoundment.
• Monitoring settlement profiles of embankments, foundations, and other structures (horizontal inclinometer)

Inclinometer Components

An inclinometer has two principal components: inclinometer casing, which is installed in the ground, and the inclinometer measurement system, which may be portable or in-place (fixed).

Inclinometer Casing

Inclinometer casing is permanently installed in a borehole that passes through suspected zones of movement. Inclinometer casing can also be embedded in fill, buried in a trench, cast into concrete, or attached to a structure.

Inclinometer casing maintains access for the inclinometer readout system, allowing the system to obtain subsurface measurements.

Portable Measurement Systems

Digitilt Classic System
Digitilt AT System

Portable measurement systems include a probe, cable, and readout. Portable systems are economical because they can be carried from site to site. They are accurate because the measurement routine involves two traverses of the casing with many readings.

A set of readings is called a survey. The first survey establishes the initial profile of the casing. Subsequent surveys reveal changes in the profile of the casing if movement has occurred.

Slope Indicator offers two portable measurement systems: the Classic Digitilt System, the world standard in precision and reliability for many years, and the Digitilt AT System, which takes advantage of newer technologies.

Inclinometer measurement systems generate large amounts of data. For example, an ordinary survey may generate several hundred data points. Over time, tens of thousands of data points must be manipulated, reduced, graphed, and archived. Slope Indicator's DigiPro software is designed to speed this process.

In-Place Measurement Systems

In-place measurement systems consist of a number of inclinometer sensors that placed at specific depths to span a zone of suspected movement. In-place inclinometer sensors are left in-place (unlike the traversing probe) and usually monitored continuously to ensure safety. The costs for an in-place system are greater because the sensors are dedicated to a particular installation.

A data logger is used with in-place sensors. It monitors continuously and can trigger an alarm when it detects a change or rate of change that exceeds a preset value. Slope Indicator typically supplies Campbell Scientific data loggers.

In-place inclinometer systems generate large amounts of data, and often the data must be processed and distributed as soon as it becomes available. Slope Indicator's Atlas web-based monitoring performs this task, automatically processing the readings, checking for alarms, and generating graphs and reports.

Spiral Checking

A spiral sensor provides readings that can be used to correct inclinometer data obtained from spiraled casing. Spiral surveys are recommended when the installation is very deep, when inclinometer readings indicate movement in unlikely directions, or when difficulties were experienced during installation.