Integrated use of GNSS and InSAR Techniques for Movement Monitoring under Trunk Road T2 and Cha Kwo Ling Tunnel

In the Trunk Road T2 and Cha Kwo Ling Tunnel (collectively “the T2”) project, a number of innovative techniques have been employed successfully. In particular, the Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) have proven to be beneficial in enhancing productivity and site safety for movement monitoring of sensitive receivers during the course of tunnel works in the T2 project. This paper reports the site application of these two innovative techniques in this tunnel project and the results of the GNSS and InSAR monitoring works. GNSS monitoring was applied to monitor the movement of the existing Public Works Central Laboratory (PWCL) Building due to the Tunnel Boring Machine (TBM) launching shaft construction works in close proximity and the movement of the seawalls and breakwater due to the crossing of TBMs underneath these marine structures, whereas InSAR monitoring was used to monitor the settlement of the existing structures in Cha Kwo Ling Village due to the T2 tunnel works. It is demonstrated that both GNSS and InSAR monitoring can effectively supplement the conventional survey monitoring.