Tre Altamira has released the first results of their close surveillance of the construction works of the Grand Paris Express scheme.
Commissioned by the Société du Grand Paris in 2015 - the public agency set up by the French Government to deliver the vision of Grand Paris Express, Tre Altamira has been surveying the construction works in order to minimise any potential impact.
Tre Altamira has monitored the project from space to the nearest millimetre, measuring the impact of the operations along its track and the adjacent areas. The satellite based solution measures the ground displacement by processing satellite radar images acquired over the same area in different points in time.
A retrospective study of the ground motion was conducted over the 200km of the Grand Paris Express network, with historical ground motion mapped with an inventory of the soil surface behaviour from April 1992 to March 2015. This identified vulnerable constructions before the start of any work.
The mapping was generated from the processing of archived images acquired since the early 1990s to 2010 by medium-resolution satellites from the European Space Agency, and by high resolution satellites from the Italian and German Space Agency for 2011-2015.
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The historical was combined with historical maps and conventional geotechnical surveys to detect ground movements caused by the evolution of quarry conditions or possible slope instability. In zones where clays are found, as is the case for other Grand Paris Express project lines, it allows for the detection of soil movements caused by the swelling of the clays.
For each measured point, it is possible to see at what period the displacements have been initiated, and whether these displacements are stabilised or in progress. These observations were crossed with existing knowledge in order to better understand the cause of the motion, and to qualify potential impact when tunnelling.
Tunnelling started on the project earlier this month.
In a statement the company said: “Monitoring activities will continue during the whole project to detect and measure any ground displacements in the area with the ultimate aim of keeping the prime contractors fully informed of the impact of drilling on the surface, so that they can adapt their work accordingly.”
An overview of the project and the satellite monitoring can be seen at this video by the Société du Grand Paris.
When completed the Grand Paris Express will be the largest expansion of the existing public transport network for the Paris metropolitan area. The project will provide Paris with 68 new stations and the 200km of metro lines will be gradually put into service by 2030.
GE visited one of the largest shafts on the project. Read more about it here.