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

Lead Research Organisation: NERC British Geological Survey
Department Name: Earth Hazards & Observatories

Abstract

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

Planned Impact

TNI: The expected outcomes are an enhanced capability to monitor and assess landslide hazards across the whole 21,000km of road network by investing in this 'leapfrog' technology, moving from a traditional on site visual assessment, to state of the art, remote sensed, regional scale hazard mapping using InSAR technology. This will see huge benefits across TNI in mapping and understanding geo-hazards. Having a better understanding of the mechanisms and extend of soil movement also allows belter informed engineered remediation techniques to be considered. This also has the impact on the organisation of being able to target their limited resources at sites assessed at being at high risk.
NIR: In addition to similar benefits and impacts to TNI, an added value to NIR is the reduced requirement to have staff on active rail tracks inspecting geo-hazards.
DETI: New innovative monitoring technologies will complement past and current data in determining the risk associated with mine subsidence and the economic impact of infrastructure deformation. The InSAR technology offers the benefit of greater consistency and accuracy of ground motions with the capability of narrowing measurement intervals during periods of increased concern. The added benefit of this platform is it also provides remote monitoring methods reducing the risk to personal that previously monitored movement from within sites. The benefit of more accurate data will improve information delivered to stakeholders in the Planning Service, local Councils and Government agencies resulting in better regulation and information for decision making process. The project will also enhance and develop the relationship between DETI and scientific research in using innovative approaches in assessing risk associated with geological hazards.
The outcomes for DETI are opportunities to provide the greater capability to assess and communicate the risk posed by ground subsidence and support the planning process in determining 0m lines of subsidence with greater accuracy. This is crucial at Carrickfergus, an area of growing residential and commercial development which borders and encroaches many of the mine sites under review. This immediate outcome will form the basis of risk assessments and feed into the planning process with the anticipation of continuation of same technology for future monitoring. The main beneficiaries from the project outputs and increased knowledge with the planning authorities and the general public with increased knowledge and understanding of risk associated with ground motion.

Publications


10 25 50
Hughes, David (2016) Millimetre precision potential in Ground Engineering
 
Description 1. Variable densities of ground movement reflectors in the ERS-1/2 data.
2. Tying reflectors to specific structural members in the infrastructure is proving challenging
We are still correlating the returns with data collected from conventional monitoring technologies.
Exploitation Route Higher resolution data will be worth comparing once we have finalised the data analysis.
Sectors Construction,Transport,Other
 
Description A stakeholder workshop was held at Queens University, Belfast in September 2016. Following this one of the stakeholders has been liaising further with respect to the detail of the movement that was evident in the data. It is clear that this stakeholder would like to engage further with the data. A second workshop is scheduled for May 2017.
First Year Of Impact 2017
Sector Government, Democracy and Justice,Transport
Impact Types Societal
 
Title Ground motion maps 
Description Maps of ground motion derived from the InSAR data using the Small Baseline Subset (SBAS) approach developed by Berardino et al. (2002) 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact Too early for this 
 
Title Output files and GIS hosting of ground motion data 
Description The point dataset was exported to shapefile format and saved as: ERS_1992-2000_SBASlowres_WGS84.shp. The data were converted from the 1984 World Geodetic System (WGS84) to the Irish National Grid (ING) and loaded into an Irish National Grid ArcGIS project using the TM65_To_WGS_1984_2 transformation. Position Vector - dx=482.530000 dy=130.596000 dz=564.557000 rx=-1.042000 ry= -0.214000 rz= -0.631000 s= 8.150000. The data were exported for loading into ArcGIS and then classified to show ranges of ground movement. 
Type Of Material Data handling & control 
Provided To Others? No  
Impact Good visual representation of the ground motion. Stakeholders readily identified with the method of presentation. 
 
Description Geoblogy 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Blog: Assessing ground motion from space...by Kieran Parker
Posted on the BGS website.
Year(s) Of Engagement Activity 2016
URL http://britgeopeople.blogspot.co.uk/2017/01/assessing-ground-motion-from-spaceby.html?m=1
 
Description InSAR for geotechnical infrastructure: enabling stakholders to remotely assess environmental risk and resilience 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Presentation delivered by Dr F Cigna to an Arup hosted workshop: Remote Sensing for Geotechnical Asset Management Workshop. This was useful in establishing links with a similar project being led by Highways England.
Year(s) Of Engagement Activity 2016
 
Description Presentation to Belfast City Council 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Other audiences
Results and Impact Presentation on Understanding Underground by Alex Donald. The InSAR project was in the order of 1/3 of the presentation.
Year(s) Of Engagement Activity 2016
 
Description Science uncovered flier 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Flier prepared for the event: Science Uncovered
European Researchers Night
Ulster Museum, Belfast
Friday 30 September 2016, 7-10pm
Year(s) Of Engagement Activity 2016
 
Description Stakeholder workshops 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Two stakeholder workshops have been held. The first was a start-up meeting and the second (September 2016) provided stakeholders with the opportunity to use the GIS at Queens University, Belfast to explore the ground motion data, which is at a resolution of 100m.
Year(s) Of Engagement Activity 2016