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Slope Stability Monitoring Technical White Papers


Displacement patterns of a landslide affected by human activities: insights from ground-based InSAR monitoring 2011

Francesca Bozzano, Ivan Cipriani, Paolo Mazzanti, Alberto Prestininzi

Abstract: Landslides interacting with large infrastructures represent a major problem for the economy, society as a whole, and the safety of workers. Continuous monitoring for 23 months using an integrated platform with a ground-based SAR interferometer (GBInSAR), a weather station, and an automatic camera gave us the opportunity to analyze the response of an unstable slope to the different phases of work. The deformational behavior of both the natural slope and the man-made structures was recorded and interpreted in relation to the working stages and the rainfall conditions during the whole monitoring period. A typical pattern of displacement was identified for shallow landslides, debris produced by the excavation and gabions, metallic walls, and anchored bulkheads. Furthermore, insights into the dynamics and behavior of the slope and the man-made structures that interact with the landslide were obtained. Extreme rainfall is the main trigger of shallow landslides and gabion deformations, while anchored bulkheads are less influenced by rainfalls. Movement of debris that is produced by excavations and temporary metallic barrier deformation are closely related to each other. The herein proposed monitoring platform is very efficient in monitoring unstable slopes that are affected by human activities. Moreover, the recorded patterns of displacement in the slope and the man-made structures can be used as reference data for similar studies and engineering designs.

Key words: GB-InSAR  Interferometry  Landslide  Monitoring  Displacement Infrastructure.

This paper was published by Springer Science+Business Media. For details on how to access this paper in pdf form, please clickhere

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Radar-based Measurement of Deflections on Bridges and Large structures: Advantages, Limitations and Possible Applications 2009

C. Gentile

Abstract: The microwave interferometry has recently emerged as an innovative technology, suitable to the non-contract vibration monitoring of large structures. New radar systems - entirely designed and developed by Italian researchers - are now available and capable of simultaneously measuring the static or dynamic deflection of several points on a large structure with high accuracy.

In the paper, some concepts of the main radar techniques (high resolution radar waveforms, phase interferometry) adopted in the radar-based measurement of deflections are first summarized, in order to highlight advantages and potential issues of the new technology and to properly discuss the technical characteristics of microwave interferometers. Subsequently, the accuracy and simplicity provided by the radar techniques in a live-load static test and ambient vibration tests performed on full-scale bridges are presented and discussed.

Key words: Ground-based SAR; Microwave Interferometry; Bridge and Structure Deflections.

To download this white paper in pdf form, please click here
 

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Near Real-Time Monitoring Of Displacements with the Ground Based SAR IBIS-L 2009

Sabine Roedelsperger, Matthias Becker, Carl Gerstenecker, and Gwendolyn Laeufer

Abstract: Within the Exup´ery Project of the German Early Warning Systems program in the Geotechnologien framework, a Volcano Fast Response System (VFRS) is being developed by a consortium of German Universities (see http://www.exupery-vfrs.de). One component of the VFRS is a ground based hybrid deformation monitoring system which combines areal measurements of the ground based SAR IBIS-L with GPS measurements at discrete points. IBIS-L operates at a frequency of 17.2 GHz (Ku-band) with a synthetic aperture of 2 m. The achievable spatial resolution is 0.75 m in range and 4.5 mrad in cross-range. From April to August 2009 a prototype of the VFRS was installed at the Fogo volcano on Sao Miguel, Acores.

The image sampling rate of ground based SAR is in the order of several minutes and the number of images can easily reach several thousands. The conventional Persistent Scatterer Interferometry (PSI) technique developed for spaceborne SAR would therefore result in an unacceptable computational effort. Here a sequential PSI analysis is described that allows the near real-time computation of displacements. First results from the processing and analysis from data gathered during the field test on the Acores and others are presented.

Key words: Ground-based SAR; IBIS-L; Persistent Scatterer Interferometry.

To download this white paper in pdf form, please click here

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Monitoring of the Manhattan Bridge for Vertical and Torsional Performance with GPS and Interferometric Radar Systems 2009

L. Mayer, B. Yanev, L.D. Olson, and A. Smyth

Abstract: This paper describes monitoring of the vertical and torsional displacements of the midspan of the Manhattan Bridge using Interferometric Radar and Global Positioning Systems (GPS). The Manhattan Bridge is a particularly interesting case study due to its immense size, unique loadings, high traffic volume, age, and recent multimillion dollar rehabilitation and stiffening program. The Interferometric radar system is an non-contacting, innovative microwave radar sensor (IBIS-S) used to simultaneously measure the displacement response of multiple locations of a structure from distances up to 0.5 kilometer. GPS systems use triangulation from satellite signals to accurately locate the absolute position of a receiver and are routinely used in a variety of applications. The systems were employed to measure the midspan deflections of the bridge under normal automobile and train traffic loadings. The GPS data characterizes the maximum deflections as well as deflection time histories of the outer roadway edges at midspan. The data acquired using the Interferometric Radar system characterized the maximum deflections as well as deflection time histories simultaneous at 80 points along the midspan with a set-up and test time of about 3 to 4 hours. Both measurement systems compared well with one another and are promising technologies in the area of bridge deflection and vibration measurements.

Key words: Interferometric Radar, Remote Testing, Bridge Monitoring.

To download this white paper in pdf form, please click here


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