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Summary of Proposal CAL1140

TitleRadar Interferometric Monitoring of Surface Settlements due to Shield Tunnelling at the Wehrhahnlinie in Düsseldorf (Germany)
Investigator Mark, Peter - Ruhr-University Bochum, Collaborative Research Centre 837 (DFG)
Team Member
Dr.-Ing. Riedel, Björn - TU Braunschweig, Institut für Geodäsie und Photogrammetrie
Prof. Dr.-Ing. habil Mark, Peter - Ruhr-University Bochum, Collaborative Research Centre 837 (DFG)
SummaryThe research team consists of two interacting research groups, one at Ruhr-University Bochum and the other one at TU Braunschweig, both with different key activities under the auspices of the Collaborative Research Centre SFB 837. In the first step, the team of TU Braunschweig (Co-PI Dr. Björn Riedel) evaluates scenes from the TerraSAR-X satellite to derive information about settlement rates taking place in the area of interest. Therefore, the Interferometric SAR (InSAR), especially the Persistent Scatterer Interferometry (PSI), will be used for that task. The once processed project data will then be interchanged by a Geo Information System (GIS) to the SFB 837 in Bochum. This specific interchange will be supported by subproject D1. In the second step, the processed displacement data form a well-founded base for civil and computational engineers working on many subprojects of SFB 837, e.g. soil modelling or building settlement. A main focus within the SFB 837 is laid on the enhancement of realistic forecast and minimization of soil redistributions due to shield tunnelling. Using the Interferometric SAR technique enables to image the integral extent and pattern of soil redistributions. Conventional measurements (e.g. tachymetric survey, levelling) are not able to give a conscious awareness of the complete displacement pattern in the area of interest, as they are restricted to particular points or lines, whereas methods based on SAR Interferometry allow us to keep an eye on inhabited areas entirely. Considering this background, the benefit for our research is primarily seen in two fields: a) Calibration of newly derived models, methods and design concepts b) Determination of actual subsidence of existing structures by means of vulnerability analyses The aim of a) is to test, calibrate and enhance the sophisticated and interlinked models by employing the PSI-derived displacements. Ideally the influence of e.g. the wheel-soil interaction to the surface-settlements can be investigated and simulated in greater details. Its outcome will be an integral model to describe the holistic process of excavation and tunnelling considering their entire facets. Calibration and verification will gain even more importance in later project phases, which rely on these models. According to b) we are going to investigate immediate consequences of surface settlements to the damage risk of existing structures beyond the tunnel axis. For this purpose the PSI-derived displacements of the urban area will be compared to available results of the conventional measurements which allows for assessment of data quality. Subsequently, the quality of satellite data can be verified. Secondly, realistic displacements, torsions, and tilts of buildings will be calculated with the data in subproject D3. With the aid of vulnerability analyses the sensitivity of typical intra-urban structures concerning the mentioned displacements will be investigated. Additionally, acceptable rates of tilt and torsion can subsequently be derived and/or accordingly existing rates can be verified by the results of vulnerability analyses. In a later project phase it is intended to develop so-called risk-profiles of building damage due to the settlements by tunnelling. Considering the fact that the time-slot to get meaningful data – for the region of our interest – from the TerraSAR-X satellite is limited, we prefer to use the High Resolution Spotlight Mode, with a repeat cycle of 11 days. The preferred angle of incidence for all scenes is 45°. With High Resolution Spotlight Mode we intend to compensate the limited number of scenes available by maximising the number of Persistent Scatterers points. Furtheron, we also intend to use of archived scenes from the EOWEB to extend our analyses to any time before April 2011. The evaluation of subsidence by using TerraSAR-X satellite data in this project is financially supported by the DFG Collaborative Research Centre SFB 837.

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