Underground Construction in BudapestTerraSAR-X-based analysis of surface movement phenomena related to underground construction in Budapest
Infrastructure constructions, excavations and underground engineering can cause movements of the Earth’s surface. These typically happen very slowly yet may have sudden and far-reaching effects that endanger infrastructure or even human lives. Today underground civil engineering projects are particularly complex tasks when conducted in the densely populated areas of large cities.
Construction of a New Metro Line in Budapest
In the Hungarian capital Budapest a complex building project was initiated in 2006, when the founding stone was laid for the construction of a new Metro line almost crossing the entire town.
Metro Line 4 is planned to connect South West Budapest with the North Western parts of the city, comprising 16 stations along a length of 12.7 km, to be completed by 2013.
Building of the Line 4 Tunnel
The tunnels of the new line are constructed using underground tunnel driving machines, while the stations are constructed by a top-down method.
During the construction, an extensive terrestrial surveying programme was established in order to monitor surface movements related to the construction, which could potentially endanger not only human lives but also the historic heritage-protected buildings of the city.
[top] PSI Analysis in the wider area of Station Szent Gellért tér based on 43 TerraSAR-X satellite data sets; [middle] Focused SBAS Analysis in the area of Station Szent Gellért tér; [bottom] Sample time series of surface displacements showing the highly
Satellite Monitoring and Surface Movement Mapping
In addition to the customer terrestrial surveillance campaign, Airbus Defence and Space experts conducted a monitoring campaign using 43 TerraSAR-X StripMap scenes of the target area, acquired between October 24th, 2008 and April 16th, 2010.
The aim of the project was to confirm the suitability of satellite based surface motion monitoring to resolve surface movements related to underground construction works in the urban area. For this aim, results derived from TerraSAR-X data were compared to the terrestrial surveying.
Sub-centimetre Precision from Space
The TerraSAR-X data was analysed using Persistent Scatterer Interferometry (PSI) and Small Baseline Subset Interferometry (SBAS) techniques which determine movements of the ground surface with sub-centimetre precision by analysing the change in the interferometric phase of the radar backscatter over time.
This interferometric technique makes use of the fact that the phase of the radar signal, transmitted by the sensor and reflected from the ground is proportional to the distance between the satellite and the point on the ground from which the signal is reflected. Thus a change in the interferometric phase of the reflected signal is proportional to the potential surface uplift or subsidence in that time frame.
Surface Displacements: Up to 10 Millimetres
Surface subsidence is made visible in the red colour scale, while surface uplifts are colour-coded in the blue colour scale.
From the map it is clearly visible that surface movements have occurred along a line from North East to South West of the river Danube, which correspondends exactly to the track of the subway construction of the new Metro Line 4. Significant surface displacements of up to approx. 10 mm per year were detected especially in the vicinities of the underground stations.
Underground Construction in Budapest