Slope Monitoring of a Road Embankment by Using Distributed Optical Fibre Sensing Inclinometer

Abstract

Distributed Optical Fibre Sensor (DOFS) is a versatile sensor considering that it can be used to measure various parameters, such as detection of small strains over large areas and long distances. The application of DOFS is currently being explored as an early warning system, particularly for slope movement detection. In this paper, an embankment slope at Sungai Rual, Jeli, Kelantan, Malaysia was selected to determine the best monitoring layout for landslide detection. Two methods of installation for vertical Fibre Optic (FO) inclinometers (using conventional casing with a special grove) were installed to monitor subsurface horizontal ground movements. The first method of FO inclinometer installation uses concrete (grade 35) grouting, and the second method uses a bentonite mixture. It was found that the first method was unsuccessful due to the fibre breakage during the hardening process of concrete and hence not recommended. However, the measurement was successfully taken for the bentonite mixture method. The displacement reading was taken using both the FO and conventional inclinometer probe. The reading for the 9.5 m depth of the inclinometer casing were recorded for the comparison between FO and conventional inclinometer probes. A comparison between FO and conventional systems showed almost similar results to the conventional method. The FO inclinometer developed in this project shall provide vital information to assist designers and operators, as well as inform stakeholders on the integrity of their structures.