Researchers at Imperial College have released a map showing ground movement across London, which highlights Crossrail tunnelling.
Using radar interferometry to detect movement within 1mm accuracy with advanced algorithms, satellite images were taken between May 2011 and April 2017 to measure where ground has moved.
In the image shown below, red corresponds to subsidence and blue to uplift, up to 2mm, while black areas are mainly parks and the Thames, where no measurement points can be retrieved.
The red line corresponds to subsidence caused by tunnelling for Crossrail and the red spot just East of Canary Wharf is caused by dewatering of the deep Chalk aquifer, which was necessary for Crossrail’s construction.
Notable movement is shown underneath Brick Lane and crossing Regent’s Park for electrical ducting projects, as well as the settlement caused by the start of the Northern Line Extension Project near Kennington Park.
According to researchers, the areas of uplift (blue) found south of the Thames are yet to be explained but may reflect seasonal changes in groundwater.
The Crossrail Learning Legacy has provided free access to their ground-based monitoring data which made it possible for the researchers to validate the remotely sensed measurements.
The research is a collaboration between Imperial College and Tre Altamira and part of student Christine Bischoff’s PhD project. It is supervised by Imperial College’s Philippa Mason, an expert in GIS and remote sensing, and Richard Ghail, specialised in geotechnical engineering, and Alessandro Ferretti, CEO of Tre Altamira and a leading authority on radar interferometry.
Last month Tre Altamira released the first results of their close surveillance of the construction works of the Grand Paris Express scheme.