How inclinometers assist geotechnical monitoring

Inclinometers have been around for many years and are an important tool used to monitor the deflection (degree of tilt) of important assets (like retaining walls).

They are a simple, cost-effective, piece of equipment that usually consists of a hollow PVC tube with two sets of internal grooves which allow measuring wheels to measure deflection in two directions.

Inclometer 1

Inclometer 2 B

The installation of slope inclinometers helps to determine the following:

  • The nature of deformation patterns, i.e., isolated, or extensive, within a slope or embankment
  • The rate of deformation, i.e., accelerating, decelerating or steady
  • Whether the deformations are within relevant limits for the project

Signs of a potential failure

Inclometer 3


Examples of the type of data obtained from inclinometer.

How they are installed

Inclinometers are typically installed in two ways:

  • Inside the structure whose deflection they want to monitor (e.g. inside of a shoring pile to measure the deflections of a retaining wall during bulk excavation); and
  • Inside boreholes, which have been purposely drilled to install the inclinometer and obtain a detailed sub-surface profile at the inclinometer location. Upon completion of the drilling, the inclinometer casing is lowered into the open borehole and grouted in.

Two sets of perpendicular grooves are present within the inclinometer casing which allows the deflection to be measured in two directions. Using either manual or automatic measuring equipment, the local ‘tilt’ and cumulative deflection of the ground or assets can be determined to a high degree of accuracy.

Inclinometers can be installed vertically or horizontally depending on which direction you want to monitor deflections. A vertical inclinometer will provide information on the horizontal deformation of the ground, whereas a horizontal slope inclinometer will demonstrate characteristics of vertical movement.

Ideally, inclinometers should be installed before any excavation works take place to get an accurate baseline position (it’s no good monitoring if your wall has already moved 20 mm!).

Inclinometers are an incredibly simple piece of equipment, however, the process of taking deflection readings requires incredibly precise measuring equipment. This measuring process is either performed manually, using digital gauges which store the deflection readings at fixed depth/length intervals for each direction, or automated measuring systems which can take deflection readings at timings set by the owner and upload results to a server so that near-continuous monitoring can be performed without the need for anyone to visit the site.

Automated inclinometer measuring systems are an incredibly useful tool for monitoring the deflection of high-value assets or at locations which are high-risk entry such as the rail corridor, as the need for someone to be onsite regularly has been removed.

When would an inclinometer be necessary?

Inclinometers are used across a variety of geotechnical projects. An engineer may install an inclinometer to assist with the following objectives:

  • Landslide investigations
  • Monitor slope stability
  • Monitor retaining structure performance
  • Monitoring excavations near important assets or major roads
  • Monitoring pile and drilled pier performance
  • Monitoring settlement of embankments
  • Monitoring deformation of pavement base
  • Monitoring performance during tunnelling

Get in touch

Douglas Partners has extensive experience with inclinometers and can assist with the installation and monitoring on your project.

Contact your local Douglas Partners office here.