Subway Tunnels Identification Through COSMO-SkyMed PSINSAR Analysis in Shanghai

Zhiying Wang - HITSZ Daniele Perissin - CUHKHui Lin - CUHK

Subway development in Shanghai

2008 2010

4 new lines and 2 extensions

From 2010 to 2020: 5 extensions, 8 new linesTotally there will be more than 20 lines

Subway development in Shanghai

Soil composition in Shanghai city center

large void ratio, high plasticity, poor permeability, high water content, low shear strength, and low modulus of

deformation.

High probability of subsidence

Previous subsidence studies in Shanghai

D. Perissin and T. Wang,Time-Series InSAR Applications Over Urban Areas in China, IEEE J-STARS, 4(1):92 – 100, 2010

(a) PS technique (1993 – 2000) (b) optical leveling (1990-1998)ESA, 40 ERS data images

New data availability in Shanghai: Cosmo-SkyMed

33 high resolution/frequency X-band SAR images

Methodology: InSAR multi-temporal processing

PS-InSAR single master config.

deformation model: linear in

time

Master scene; Oct. 2009

Identification of independent targets (discarding dependent pixels) Estimation of double scatterers in a single resolution cell Estimation of a seasonal trend for targets laying on high buildings Estimation of target life time to detect also temporary targets

Processing tool used in this study: SARPROZ

http://ihome.cuhk.edu.hk/~b122066/index_files/download.htm

Written in Matlab, graphical interface, advanced options,

processing, data visual./export.

Shanghai Huang Pu, Lu Wan, Jing An and Zha Bei, 600 sqkm

~1.5 Million PS’s

Results and analysis

Results and analysis

Close up of subsidence mapand superposition of Metro stations

Deformation detail – localization

The precise location of the subway tunnels is not public. With radar data, through the surface deformation, we can precisely

track the new lines built recently.

Example of 3D visualization. The color indicates the PS Height

Example of 3D visualization. The color indicates the PS Height

Deformation detail – Xiaonanmen

Subsidence happens mostly on the ground or on low buildings

Near Xiaonanmen station – line 9

High buildings

Metro tunnel

SARPROZ visualization tool

High buildings

tunnel

SARPROZ visualization tool

Deformation detailAmplitude and phase time

series

Deformation detail – profile of the subsidence

Subsidence width: > 90m; The width of the inflexion is around 60m; maximum subsidence: 18mm/year

Deformation detail - profile of the subsidence

Idealized settlement curve

Kz= 18m and Smax=18mm

when the radius= 3.2m

The real curve depends on many factors,it may not be symmetric.

Tunnel information of detected line 9 and line 10 the external diameter: 6.4m. The distance between two central lines of tunnels is about

20m !!! Very good agreement (18*2+20=56m)

Conclusion

Advantages: PS-InSAR with Cosmo data is able to monitor subsidence of metro

tunnels in most cases PS-InSAR with Cosmo data is able to monitor the subsidence of

buildings beside tunnels – (tunnel monitoring systems cannot) We can precisely localize and track newly built tunnels with high

details The whole line can be consistently monitored (global monitoring

method)

Disadvantages: PS density is depending on the observed area (e.g. on wide roads

there are few PS’s).

Ongoing works: Results validation with ground data New project in Hong Kong for monitoring new tunneling works

Thank you!