Abstract
Subways have been an important method for relieving traffic pressures in urban areas, but ground subsidence, during construction and operation, can be a serious problem as it may affect the safety of its operation and that of the surrounding buildings. Thus, conducting long-term ground deformation monitoring and modeling for subway networks are essential. Compared with traditional geodetic methods, the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique offers wider coverage and denser measurements along subway lines. In this study, we mapped the surface deformation of the Guangzhou subway network with Advanced Synthetic Aperture Radar (ASAR) and Phased Array Type L-band Synthetic Aperture Radar (PALSAR) data using the Interferometric Point Target Analysis (IPTA) technique. The results indicate that newly excavated tunnels have regional subsidence with an average rate of more than 8 mm/year, as found on Lines Two, Three, Six, and GuangFo (GF). Furthermore, we determined the spatio-temporal subsidence behavior of subways with PALSAR in delta areas using Peck’s formula and the logistic time model. We estimated the tunneling-related parameters in soft soil areas, which had not been previously explored. We examined a section of line GF, as an example, to estimate the ground settlement trough development. The results showed the maximum settlement increased from −5.2 mm to −23.6 mm and its ground loss ratio ranged from 1.5–8.7% between 13 July 2008 and 19 January 2011. In addition, we found that the tunnels in line GF will become stable after a period of about 2300 days in peak subsidence areas. The results show that the proposed approach can help explain the dynamic ground subsidence along a metro line. This study can provide references for urban subway projects in delta areas, and for the risk assessment of nearby buildings and underground pipelines along metro lines.
Highlights
The excellent climate, beautiful landscape, and convenient waterway communication have contributed to the favorable economic development of delta regions around the world, such as Guangzhou, Shanghai, Shenzhen, and Beijing in China, Mexico City in Mexico, and Bangkok in Thailand
To provide an overview of the subsidence behavior along the metro line, we extended the analysis to a wider area from Kuiqi Lu station to Zumiao station, about 4 km, and chose 9 profiles to estimate the structural parameters, according to the PT density
The spatio-temporal analysis showed that the maximum settlement are around [5.2−23.6] mm and its ground loss ratio ranged from 1.5−8.7% between 13 July 2008 and 19 January 2011 in GF line
Summary
The excellent climate, beautiful landscape, and convenient waterway communication have contributed to the favorable economic development of delta regions around the world, such as Guangzhou, Shanghai, Shenzhen, and Beijing in China, Mexico City in Mexico, and Bangkok in Thailand. Vulnerable geological conditions plus sediment loading, compaction, and human activities, including groundwater and hydrocarbon extraction, have led to different degrees of subsidence These human activities all significantly impact subway construction and operation, so surface subsidence monitoring along any subway under construction and operation is necessary. Only a few ground deformations, related to subways in delta areas, have been identified [16,17,18,19,20,21,22], and little work has used InSAR observation to study tunneling parameters, such as the maximum settlement, ground loss, and settlement trough width. This study attempted to use InSAR measurements to monitor the surface deformation along subway lines and determine the tunneling-induced deformation parameters.
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