InSAR for geotechnical infrastructure: enabling stakeholders to remotely assess environmental risk and resilience

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The three stakeholders in this project, Transport Northern Ireland (TNI), Northern Ireland Rail (NIR) and the Department of Enterprise, Trade and Investment (DETI) all have one common need which this project addresses. They are required to monitor ground deformations across their geotechnical assets (e.g. embankments, cuttings and earth retaining structures) using the most efficient, cost effective methods, with a view to minimising and managing the geotechnical risk to their businesses and the road/rail users. The objective of the work therefore is to apply the methodologies that the British Geological Survey (BGS) have already developed through past research projects of assessing the deformation of geotechnical infrastructure, such as slope movement or ground subsidence, using Satellite Interferometric Synthetic Aperture Radar (InSAR). The project will validate this methodology through ground truthing, using geotechnical monitoring and high resolution photogrammetry developed by Queen's University Belfast (QUB). Through this project, the stakeholders will be able to monitor ground deformations in a more cost effective, efficient, more thorough and more robust way, and embed the use of this methodology across their organisations making a step change on how they approach assessment and manage the resilience of their geotechnical infrastructure.TNI anticipate that the use of InSAR data will help form their strategies for monitoring their geotechnical assets and will feed into the existing GIS based risk assessment methods for their infrastructure assets. The site at Straidkilly is only one of many sections along the A2 coast road that is unstable and it is hoped that InSAR will give a much greater insight into the behaviour of a variety of geohazards that impact on the road and will inform their maintenance strategies and lead to more cost effective better targeted maintenance. TNI also are committed to having a better understanding of the mechanisms of failure on the slow moving failures on the Throne Bend in Belfast. The InSAR data will allow a much better correlation between slope movement and rainfall intensity and duration to be undertaken. InSAR data will also allow better mapping of the extent and magnitude of the instability. NIR also hope to be able to correlate the slope instability against rainfall data on the Belfast-Bangor rail line. DETI anticipate that the project will validate new methods of monitoring and provide baseline data of ground motion to form the basis of future strategic decisions in regards to geohazards. The use of InSAR at sites in Carrickfergus will potentially provide greater knowledge of extent of subsidence boundaries and provide indicators to potential catastrophic collapse by analysing SAR data against periods of known rapid collapse of ground.Keywords: geotechnical infrastructure, subsidence, slope instability, remote sensing, radar interferometry (InSAR), ground motion monitoring