Historical Analysis of Tunnel Approach Displacements with Satellite Remote Sensing

Historical displacements of tunnel boat sections at the approaches to the Monitor–Merrimac Memorial Bridge–Tunnel (MMMBT) in Virginia were investigated as a potential reason for ongoing seawater infiltration. Archived data collected from December 2001 to March 2010 by the Radarsat-1 Earth-orbiting radar satellite were analyzed. Millimetric precision was achieved in displacement measurements over an area of approximately 100 km², including the MMMBT and adjacent regions of Suffolk and Newport News, Virginia. Data consisting of 42 radar acquisitions were processed by using the interferometric synthetic aperture radar (InSAR) differential technique. Additional statistical analyses were conducted on selected points of interest. Results of the historical analysis of satellite radar remote sensing data indicated no significant displacements of the tunnel boat sections during the study period. The annual displacement rate precision of the tunnel boat sections was estimated to be ±1 mm/year at the 95th percentile confidence level. Thus, settlement of the constructed islands was unlikely to have been a reason for the ongoing water infiltration.