Remote Sensing Techniques for Highway Earthworks Assessment

The Highways Agency (HA) in the United Kingdom is responsible for managing 9380 km of the motorway and trunk road network in England. This includes around 7000 km of embankment and cutting slopes. Year on year costs for repairing slope failures have been increasing almost exponentially and it has been recognised that significant whole life cost savings could be achieved through implementation of an appropriate pro-active regime through preventative maintenance of marginally stable earthworks. This together with the requirement to increase capacity and reliability of the existing network have led the Highways Agency to implement specific research into the implementation of a pro-active maintenance regime for earthworks. As part of this programme, research into the use of remote sensing techniques for inspecting the network earthworks has been undertaken by the Highways Agency with the aim of improving the speed, safety, quality and repeatability of slope condition data collection and reducing disruption to road users caused by inspections. This is to allow the regular identification of at-risk earthworks slopes and facilitate the improved management of the geotechnical asset. The Remote Rapid Assessment research project comprised a series of trials to evaluate selected remote sensing techniques for highway earthworks inspections. The techniques included satellite and aerial photography, airborne laser scanning and thermal scanning and videography. This paper describes the trials and outlines the extent to which remote sensing techniques can currently identify slope instability features and assist in the asset management process. Costs and benefits associated with remote assessment are also discussed. The HA research into pro-active earthworks asset assessment is ongoing but indications are that the techniques will allow significant improvements to the current regime.