Abstract
Underground constructions are implemented in cities to relieve the pressure of urbanization. Ground deformation often occurs with improper construction activities. Such deformation can be measured with techniques such as multitemporal interferometric synthetic aperture radar (MT-InSAR). However, the deformation anomalies, such as the building horizontal tilt can cause the MT-InSAR line-of-sight deformation to tend to zero, the deformed area is likely to be ignored when the individual SAR dataset is applied. In this article, we explore deformation induced by the underground construction of To Kwa Wan (TKW) station in Hong Kong with an improved MT-InSAR method. Multiplatform SAR datasets from TerraSAR-X, COSMO-SkyMed, and Sentinel-1A are adopted to retrieve comprehensive deformation of ground buildings for stability investigation. The results are validated through cross-validation between SAR datasets. Both spatial and temporal variations of ground deformation are revealed. Ground buildings suffered significant deformation in vertical and horizontal directions, the maximum deformation is around 30 and 40 mm, respectively. Due to the anomalous deformation, the ground buildings around the station are dumped towards the street center. In view of temporal evolution, the deformation is strongly related to the construction stages. The deformation turned to be stable after the completion of the main framework of the TKW station in December 2016. This article suggests that the deformation obtained from individual SAR datasets may sometimes is not noticeable or reliable in the area with complex underground construction. Such complex phenomena can be revealed by using the multiplatform SAR datasets with MT-InSAR.
Highlights
Ground deformation in urban area often caused by artificial activities such as land reclamation [1, 2], groundwater exploitation [3, 4], and underground construction [5, 6]
Beside the well-agreement between the deformation evolution and the different stages of subway construction, we have found the geographical location of the LOS deformation on the To Kwa Wan (TKW) station is significantly different when the SAR datasets along with different observed orbital directions are used
The results show that the ground buildings suffered significant sinking deformation in the vertical direction, the maximum deformation reaches 30 mm
Summary
Ground deformation in urban area often caused by artificial activities such as land reclamation [1, 2], groundwater exploitation [3, 4], and underground construction [5, 6]. MT-InSAR can provide more detailed information to study the various deformation processes, which range from the large-area ground subsidence to individual infrastructure stability. The ground subsidence relating to land reclamation [22, 23], underground mining [4], and urbanization [24] has been explored with MT-InSAR benefit from its wide coverage and high resolution. The deformation anomalies can often be arbitrary in nature in 3D space especially during the construction process, which may appear as vertical subsidence and horizontal tilting It may be different from the prior assumption, incorrect conclusions will be derived. The study result has informed future deformation monitoring of underground construction process in urbanized areas.
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