Ground Movement Monitoring of Unstable Pipeline Corridors With Fiber Optic Slope Indicators

Spectra Energy Transmission (SET) owns and operates approximately 6,000 kms of raw and sweet natural gas transmission pipelines in northeastern British Columbia and northwestern Alberta. This geographic area is very susceptible to landslides and unstable land mass due principally to the local geological regime. These slope instabilities present long term operational challenges to pipeline companies. Geotechnical pipeline failures are not uncommon and pipeline operators spend significant portions of their operational budgets on geotechnical issues. SET has developed a geotechnical integrity program to take a proactive approach to these geotechnical issues. Ground movement monitoring is a significant component of this integrity program and provides physical data that becomes the backbone of remedial works. SET currently utilizes traditional slope indicators, surface survey monitoring, differential GPS, LiDar and InSar technologies to obtain this ground movement data. As an element of the geotechnical integrity program, SET utilizes fiber optic sensors to monitor the pipeline’s reaction to ground movement. After the initial installation of these fiber optic sensors, it was apparent that they could be bonded to almost any structural member. Potential to use the fiber optic sensors to extend the life of a traditional slope indicator was discussed with the sensor manufacturer and six joints of slope indicator casing were fitted with fiber optic sensors. These instrumented joints were then installed across known slide surfaces at various existing monitoring locations. Periodic data collection of both the slope indicator and the fiber optic sensors allowed for ground movement correlation up to the shearing of the slope indicator. It is anticipated that with proper installation and further design improvements from the manufacturer that the fiber optic instrumented slope inclinometers will facilitate ground movement monitoring beyond the life of the traditional slope indicator. This paper discusses the results of the initial trial, what was successful, what lessons were learned, and which pipeline scenarios would benefit from this technology and potential methodologies to monitor ground movement and pipeline bending concurrently.