| With the rapid urbanization and development of transportation infrastructure in China,urban land subsidence becomes common.The potential as a serious geological disaster in cities requires further investigation and quantitative evaluation of the subsidence.Highways are important infrastructure components related to the urbanization and residents’ lives.The surface deformation of the roads and their surrounding lands threatens the operation safety of the highways and indirectly affecting the safety of residents’ lives and property.Therefore,the quantitative evaluation of the surface deformation by various monitoring means is needed in a timely fashion.Thus,preventive measures may be taken before a disaster.In recent years,many countries and regions are developing their synthetic aperture radar(SAR)satellite programs.With the multi-temporal SAR datasets,the time-series analysis of the interferometry synthetic aperture radar(InSAR)technology has attracted great attention and becomes one of the powerful tools in the assessment of the surface deformation.The time-series InSAR technology that is typically represented by the permanent scatter interferometry(PS-InSAR)technology can not only minimize the atmospheric effects on the InSAR-derived outcomes,but also offer all-day and allweather monitoring,wide ground-coverage,high level of measurement accuracy,and low cost.The time-series InSAR technology has been widely used in the urban road deformation study.Chengdu is the central city in southwest China.In recent years,for the urbanization development of Chengdu,the demand for transportation infrastructure is enormous.The safety of the roads is paramount.In this study,the ESA(European Space Agency)C-band Sentinel-1 datasets and PS-InSAR technology were used to evaluate the surface deformation of two of the major transportation arteries,the third-ring expressway and fourth-ring expressway,and their surrounding areas.The SAR datasets consisted of sixtytwo images acquired along the ascending orbits and fifty-eight datasets along descending orbits.The time-span of the datasets was from July of 2015 to April of 2018.The spatial distribution of PSs and subsidence velocities between 2015 and 2018 were derived.The monitoring results obtained from ascending and descending orbit SAR datasets can be supplemented and compared with each other.Particularly,the subsidence near the southern and eastern parts of two expressways occurred spatiotemporal irregularly and corresponding section roads were analyzed with the time series results.With aerial coverage of the ascending orbits SAR dataset,the surface deformation of the city was analyzed.The overall deformation of the city might not be severe,but the southeastern Chengdu could be a hot spot with a relatively large rate in the surface deformation.The causes of subsidence were attributed to the local geological environment,precipitation,ground-water extraction,and construction activities. |
