Abstract
On the evening of 7 February 2018, a deadly collapse of a metro tunnel under construction in the Southern China city of Foshan caused 11 deaths, 8 injuries, and 1 missing person. For disaster prevention and mitigation, the spatiotemporal ground deformations before and after the collapse event were derived from 55 Sentinel-1A synthetic aperture radar (SAR) images spanning from March 2017 to January 2019. The results showed that prominent ground subsidence in the shape of a funnel with a maximum rate of 42 mm/year was observed in the vicinity of the collapse area before the accident. After the accident, the area and magnitude of subsidence decreased compared with precollapse subsidence. This decrease is related to the progress of tunnel excavation and groundwater changes. In the temporal domain, continuous subsidence was observed over a year before and after the accident, and accelerated subsidence appeared one month before the collapse accident. Soft soil consolidation and tunnel-induced soil losses were the main reasons for the subsidence over the study area. The leakage of groundwater accounted for the collapse event. The leaked groundwater eroded the soil, resulting in the formation of an arched hole. The connection between the arched hole and the tunnel reduced the bearing capacity of the soil layer above the arched hole, triggering the collapse event. The findings provide scientific evidence for future collapse monitoring and early warning due to tunnel excavation.
Highlights
As an advanced space observation technique, synthetic aperture radar (SAR) interferometry has demonstrated advantages for monitoring the ground deformation for collapse sinkholes compared with some ground-based instruments and techniques, such as high-precision leveling [1], robotic total stations [2], global positioning systems [3], and terrestrial laser scanner [4]
The findings provide scientific evidence for future collapse monitoring and early warning due to tunnel excavation
Using 55 C-band Sentinel-1A images, the annual deformation velocity and timeseries deformation maps before and after the event were retrieved through multitemporal SAR interferometry processing
Summary
As an advanced space observation technique, synthetic aperture radar (SAR) interferometry has demonstrated advantages for monitoring the ground deformation for collapse sinkholes compared with some ground-based instruments and techniques, such as high-precision leveling [1], robotic total stations [2], global positioning systems [3], and terrestrial laser scanner [4]. The sinkholes along the Dead Sea coast in Israel and Jordan have been successfully identified and monitored by SAR interferometry since 2002, providing rich references and experiences for studying the deformation of collapse sinkholes [5,6,7,8,9,10,11]. The collapse area is part of the shield tunnel interval between Huchong Station and Lvdaohu Station, which is 1804 m long and 17.2–34.4 m deep [20].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
