Impact of ground subsidence on the Beijing-Tianjin high-speed railway as mapped by radar interferometry

The construction of the Beijing-Tianjin high-speed railway line started in July 2005. The railway has been completed and opened to traffic in August 2008, just before the Beijing Olympic Games. The 113 km railway costing 13.3 billion Yuan (US $1.5 billion) is the country's first high-standard passenger rail. It is also believed to be the pilot project of a massive highspeed rail network in China. The train shuttles passengers between the cities in just half an hour, 45 minutes shorter than the usual travel time. The train is designed to go 200 km/h, but can reach speeds of 350 km/h. The current railway is under pressure, handling 25.55 million passengers each year. The new passenger rail line is expected to handle 32 million passengers from 2008 and 54 million passengers in 2015. Both Tianjin and Beijing have been suffering from ground subsidence due to groundwater extraction. This study focuses on mapping the impact of such subsidence on the Beijing-Tianjin high-speed railway using differential radar interferometry. Both persistent scatterer interferometric synthetic aperture radar (PSInSAR) and differential InSAR (DInSAR) techniques are used to analyse SAR data collected by ENVISAT ASAR and ALOS PALSAR sensors. The results are further analysed in GIS and compared with reported ground survey results.12 page(s