Asset managers in the transport sector are responsible for managing risk from a wide array of infrastructure. In the UK alone we have a variety of assets to operate and maintain:
Any number of these assets could be impacted by damaging ground movements. Monitoring all of these assets with traditional ground-based approaches is expensive, but the cost of failures to the asset owners and wider society is high, with risks of delays, closures and in extreme cases even a risk to life.
A number of types of ground movement that can impact earthworks. These range from shallow translational failures and washouts to deeper rotational slides. There is a risk in some cases of material encroaching on the active network, causing accidents or derailments in extreme cases. Movements can also offset the track, leading to speed restrictions and increased journey times.
SatSense data can identify ground movement before it leads to catastrophic failure. One example is the railway north of East Grinstead, where a landslip occurred in February 2020, forcing the line to close. SatSense data show that slow movement began at least 3 years prior to failure. Note after remedial works in 2020 the area has stabilised with minimal changes in displacement.
Seasonality naturally influences ground displacement - dry summer months cause the contraction of clay soils, and wetter winter periods lead to swelling of the soil. With a changing climate and more frequent occurrence of extreme weather events, it's becoming more important to re-evaluate the extent of seasonal shrink-swell fluctuations on earthworks to recognise any abnormalities or signs of distress.
The image shows bespoke shrink/swell risk indices for a stretch of railway. Areas of red indicate a high risk of shrink/swell and an associated time series (yellow box) showing the seasonal movement.
At locations where large-scale movements are known to occur, and are constantly monitored, SatSense InSAR can be used alongside traditional ground-based monitoring approaches, increasing the measurement density in space and time, and reducing both the cost of monitoring and the amount of time required next to the road/track.
At Folkestone Warren, where a very large landslide impacts the railway line, SatSense InSAR can capture the wide area ground movement. Comparison with Network Rail’s ground-based monitoring shows an excellent agreement between the ground based survey data and SatSense InSAR data. You can read all about the study by clicking the button below.
Events or activities that occur beyond the boundary fence can also be impactful to transport infrastructure. This new distribution centre was constructed in Rugby, England, which caused settlement that affected both the nearby railway line and the building itself.
Or, ground movement affecting a railway in South Yorkshire, caused by the legacy of coal mining. The highest rates of subsidence along the route are highlighted in the image below, just a small detail of a larger monitoring report generated by our InSAR technology. Any activities beyond the boundary fence that affect assets can be quickly identified.
Many of the assets that form part of the critical infrastructure of transport networks (bridges, tunnels, stations, depots etc) are only monitored with periodic visual inspections. Any small degradation or movements that occur between inspections are challenging to detect. SatSense InSAR can monitor assets over an entire network, flagging assets where there is concerning movement using bespoke algorithms, or showing assets to be stable, thus reducing the requirement for visual inspection.
In this image we see the impact of neighbouring construction on the highway and railway corridor.