Integrated analysis of SAR interferometric and geological data for investigating long-term reclamation settlement of Chek Lap Kok Airport,Hong Kong

We investigated the long-term reclamation settlement of Chek Lap Kok Airport, Hong Kong, one of the largest reclamation projects worldwide. An advanced InSAR technique was applied to two independent ASAR data sets along ascending (25 scenes) and descending (22 scenes) orbits acquired between 2003 and 2008, and allowed us to generate deformation velocity maps and displacement time series for the investigated area. Intercomparison of deformation velocity results from the two ASAR data sets and their validation against leveling survey measurements were carried out in order to assess accuracy and reliability of the InSAR observations. The intercomparison and validation results demonstrated the potential of elaborate InSAR processes on local-scale areas to monitor and detect a long-term residual settlement in such complex reclamation area. The InSAR-derived deformation velocity maps showed a fair stability in areas of the two original rocky islands of Chek Lap Kok and Lam Chau, and on most of the buildings at the site due to foundation on piles reaching the granite bedrock, whereas a generally moderate (3–7 mm/year) to strong (> 10 mm/year) and spatially variable settlement trend was detected in the majority of reclamation areas of the airport. The consistent relationship we found between the observed settlement pattern and the underlying geological conditions suggested that this recoded differential settlement was mainly related to the variations in thickness and soil properties of both the fill materials and the alluvial deposits below the reclamation. A geological and geotechnical interpretation of the lithostratigraphy of the alluvial deposits beneath the reclamation implied that the relatively large settlement rate measured up to 2008 was resulted from a still active primary consolidation process.