Spatial and temporal deformation characteristics of marine alluvial deposits due to land reclamation: implications from InSAR observation and geotechnical estimate

Ground deformation of reclaimed land is a key issue for reclamation design, construction and sustainable development in coastal areas as this consolidation process of the underlying compressible marine sediment sequences over very long-time periods could lead to damage of both ground constructions and underground facilities. In this case study, we have investigated the spatial and temporal characteristics of residual reclamation settlement of Click Lap Kok Airport, Hong Kong, one of the largest land reclamation projects worldwide. A total of 25 time series ENVISAT ASAR datasets, acquired between December 2003 and October 2000, were used to retrieve settlement rates and deformation history at high resolution and accuracy by means of advanced Synthetic Aperture Radar Interferometry (InSAR). The InSAR-derived results show a fairly homogenous and stable pattern in the sectors of the airport site corresponding to the two original islands of Click Lap Kok and Lam Chau. In contrast, a relatively high spatial settlement variability, ranging from moderate (3-7 mm/yr) to strong (>10 mm/yr) settlement rates, was discovered within the majority of the reclaimed portion of the airport. A joint analysis of InSAR observations and geological materials indicates that the variability of the recorded residual settlement was highly correlated with the variations of thickness and pre-consolidation state of alluvial deposits below the reclamation. A quantitative comparison analysis also has been carried out between time series InSAR observations and theoretical estimates of residual settlement modelled by geotechnical investigations. The results imply that a primary consolidation process in alluvial deposits below the reclamation might lie delayed with respect to the predicted results and may still have been occurring in most reclaimed areas during the investigation period (2003-2008); the time to complete it could stretch to decades depending on hydraulic conductivity and natural drainage conditions. Copyright (C) 2010 John Wiley & Sons, Ltd.