Fibre optic inclinometer sensor

Inclinometers are devices for monitoring movements of natural slopes or man-made slopes such as embankment dams, open cut excavations, etc. The conventional inclinometers measure the lateral deformation by means of a probe passing along a casing installed either in a borehole or in fill. In spite of being widely used, the inclinometers are of limited use for remotely continuous measurements of displacement since the displacement is measured when the sensing probe is manually lowered into the casing. As far as monitoring of slope movement is concerned, continuous measurement will provide the basis for early warning systems and real-time monitoring and forecasting of slope movement behaviour. But also the attributes of inclinometers concerning the damage in case of large displacements need to be improved. An investigation has been performed to develop a new inclinometer device using fibre optic approach. A fibre optic cable was attached to the outer surface of a plastic pipe in two loops. Each half of the loop made up one quadrant of the circular section of the plastic pipe. As the fibre cable was firmly fixed to the pipe, any stress acting on the pipe will be transmitted to the fibre cable. The experiment results reported in this Paper indicated that this technique give the possibility in performing real-time continuous measurement of both direction and displacement of slope movements.