Use of InSAR data for building deformation monitoring

Abstract

This thesis explores the use of InSAR data for building monitoring. The area of main interest is the city centre of Amsterdam, where quay wall replacements are necessary on a large scale. In Amsterdam, the foundation quality needs to be checked before construction activities nearby are performed, such as a quay wall replacement. Levelling benchmarks are usually installed to determine building deformation. In case large deformation rates are observed, additional measures are taken to ensure no building damage occurs during construction. Interferometric Synthetic Aperture Radar (InSAR) measures deformations from space and provides multiple years of deformation measurements. This can therefore reduce required monitoring time before construction.
In this thesis, the use of InSAR for building deformation monitoring is investigated by analysis of occurring deformations of three areas in the city of Amsterdam. Furthermore, deformation in the Spoorsingel area in Delft is analyzed since large deformations are observed here. In all cases, levelling benchmarks are available for comparison of deformations.
The results from the Amsterdam cases indicate similar building deformation behaviour by InSAR and levelling. Differences between InSAR and levelling are suggested to be the result of the measurement location and non-uniform building movement. In the city centre of Amsterdam, buildings with more than 2 mm/y settlement require additional attention. In this regard, a probabilistic approach is proposed. The probability of exceeding the 2 mm/y threshold is calculated by combining the calculated deformation rate with the variance of this estimate. This method is not only useful for InSAR displacement time series but also for other monitoring methods such as levelling, where the amount of measurements is often limited.
Furthermore, the InSAR data enables the identification of building deformation mechanisms such as rotation, as is observed for the Spoorsingel in Delft. To identify this movement, rigid building behaviour is assumed. For buildings in plane-strain situation a method is devised to calculate the three dimensional deformation, using the ascending and descending track of a Synthetic Aperture Radar.
All in all, the InSAR data is of added value to determine the building deformation behaviour. For this, the location precision, the quality of the time series, the line-of-sight measurement and the variance of the deformation rate estimate should be taken into consideration. A flow chart is proposed which describes the use of InSAR for building monitoring.