Integrating geotechnical and interferometric SAR
measurements for secondary compressibility
characterization of coastal soils
L. Tosi
Institute of Marine Sciences, CNR, Venezia, Italy
P. Teatini
Department of Civil, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
L. Bincoletto
Geological consultant, San Vito al Tagliamento, Italy
P. Simonini
Department of Hydraulic, Maritime, Environmental and Geotechnical Engineering, University of Padova,
Padova, Italy
T. Strozzi
Gamma Remote Sensing, Gumligen, Switzerland
ABSTRACT
Persistent scatterer interferometry (PSI) provides a new perspective to monitor
the movements of coastal structures due to long-term consolidation using satellite-borne
remote sensors. The method has the advantages of detecting the displacements at a very
high spatial (from 1 to a few meters) and temporal (from 10 to 30 days) resolution. Cost-effective
monitoring of complex and large (some kilometer long) structures can be done
over long time (up to 10 years) intervals and at large scales (tens times tens km2<) of
investigation. Here, these measurements are integrated with geotechnical, site-specific
measurements to characterize in a unique framework the long-term compressibility of
coastal soils over large areas. The approach is tested on the 60-km-long coastland of the
Venice Lagoon, Italy. An accurate quantification of the movements of coastal infrastructures
at the Venice coastland is carried out by PSI using ENVISAT ASAR and TerraSARX
images acquired from April 2003 to December 2009 and from March 2008 to January
2009, respectively. Several nearshore and offshore structures were constructed over the
decades to protect Venice and its coastal environment from sea storms and high tides. Long
jetties were built at the lagoon inlets since the end of the 18th century, significantly
reinforced between 1994 and 1997, and finally reshaped since 2003 in the framework of the
MOSE construction (i.e., the project of mobile barriers for the temporarily closure of the
lagoon to the sea). The measured displacements range from a few mm/year for the
structures older than 10 years to 50-70 mm/year for those realized a few years ago. The
PSI measurements are combined with the outcome of a detailed geomechanical characterization
of the lagoon subsoil obtained by a field-scale experiment started at the end of
2002 and monitored to 2008. The use of the stress-strain properties derived from the trial
embankment and the actual lithostratigraphy below the coastal structures, which is
available from several piezocone profiles and boreholes, allows for the computation of
secondary compression (consolidation) rates that match very well the PSI-derived movements.
The results provide important information on the potential of using PSI to characterizing
geotechnical properties (magnitude and distribution) of coastal deposits, as well
as to estimate the expected time-dependent geomechanical response of coastal structures or
other large constructions.
