The inclinometer measurement
Using an inclinometer it is possible to detect deformations or shifts in the subsoil. Inclinometer measurements are a standard procedure in geotechnics. In underground construction and foundation building, inclinometer measurements are used in multiple ways. With the help of a mobile inclinometer, the incline of a borehole can be measured producing an incline profile.
Through repeated measurement cycles it is possible to determine how the subsoil has changed as a result of the construction activities or from naturally occurring settlement. In this way it is possible to detect slippages of embankments, deformations of retaining walls, settlements of foundation soil and other deeper shifts in the subsoil. With an inclinometer measurement tilting of retaining walls or other changes in the foundation soil can be monitored during the construction phase using an integrated measurement conduit.
Most frequently inclinometer measurements are used to document drilling verticality, as a means of monitoring horizontal slippage and to determine any movements in buildings and other structures. While settlement measurements can only be conducted at the surface, with inclinometer measurements it is possible to check what is happening with structures at a deeper level.
The inclinometer measurement can be used in two situations – as a vertical measurement or as a horizontal measurement. Slippages and monitoring of retaining walls are instances of vertical inclinometer measurements. Checking settlements and roadway monitoring are examples of horizontal inclinometer measurements. The inclinometer measurement gives a clear and exact indication in graphic or in table form of any movement that has taken place.
The inclinometer consists of a two-way tilt sensor with which the inclination in two main directions is shown – either an inclination of decline (axis A) or at an adjacent 90° auxiliary angle (axis B)
Procedure for taking an inclinometer measurement
To begin with a blind probe is sent through the measurement casing to check if it is passable. Then the actual probe is introduced into the flexible measurement casing and the incline is determined along both measurement axes at regular intervals. Two readings are taken at each measurement point to reduce the level of error. Using these values the course of the borehole as well as any deformations, error values and average values are determined. With these various elements, it is possible to determine what the condition and developments in the subsoil are.
Zero offset and follow-up measurements
To obtain valid and complete data, an initial zero offset measurement is taken to use as a reference. Then at regular intervals follow-up measurements are taken which can be supplemented with measurements at special points in time (when certain construction milestones are reached, for example).
Deviations from a perpendicular value or horizontal value are shown in graphs and tables. Continuing inclinometer measurements make it possible to see changes in comparison to previous measurements. Using inclinometers from the company GLÖTZL, Buck Surveying in Kassel offers a full range of inclinometer measurement services.