Development of distributed fibre optic inclinometer for landslide and geotechnical application

Geotechnical instrumentation and monitoring works are essential for the successful completion of geotechnical projects particularly for critical ones such as tunnels, slopes, embankment and ground excavations next to sensitive structures. However, most conventional geotechnical instruments are limited to discrete sensing (they may miss the critical location of soil movement), high cost, and susceptible to various reading errors (e.g. electromagnetic interference). These problems can be overcame using a novel Distributed Optical Fibre Strain Sensor (DOFSS). As investigated and presented in this paper, the DOFSS is incorporated using a Brillouin Optical Time Domain Analysis (BOTDA) interrogator that measures strain and temperature at every 5 cm along the whole length of an optical cable for kilometers long. The paper presents how this technology can be used to monitor vertical and horizontal ground movements as well as the data processing technique involved. Distributed optical fibre inclinometer is developed through laboratory pipe bending tests where the data is corroborated with conventional instruments. A simplified cost comparative study between DOFSS and conventional geotechnical instrumentation indicates the new technology is cost-effective for applications in slope and embankment monitoring particularly when monitoring large number of borehole points and measurement arrays. Copyright © Soil Mechanics and Geotechnical Engineering, ARC 2019.All rights reserved.