Abstract
The ancient city of Xi’an, China, has been suffering severe land subsidence and ground fissure hazards since the 1960s, mainly due to the over-withdrawal of groundwater and large-scale urban construction. This has threatened and will continue to threaten the stability of urban infrastructure, such as the construction and operation of high buildings and subway lines. It is necessary to map the spatiotemporal variations of land subsidence over Xi’an, and to analyze their causes and the correlation with underground water level changes and ground fissure deformation. Time series of land subsidence were observed with the interferometric synthetic aperture radar (InSAR) technique, using multi-sensor SAR datasets from 2012 to 2018. Four land subsidence rate maps over Xi’an city were retrieved from TerraSAR-X, ALOS/PALSAR2, and Sentinel-1 data, each with different tracks. The InSAR derived results were then cross-validated with three independent SAR data stacks, and calibrated with GPS and leveling observations. Next, the spatiotemporal evolutions of three main regional land subsidence zones were quantitatively analyzed in detail, and the surface deformation of the Xi’an subway network was spatially analyzed. Third, the correlations between land subsidence and ground water withdrawal, ground fissure deformation, landforms, and faults were intensively analyzed. Finally, a flat lying sill model with distributed contractions was implemented to model the InSAR deformation over one typical subsidence zone, which further suggested that the ground deformation was mainly caused by groundwater withdrawal. This systematic research can provide sound evidence to serve decision-making for land subsidence mitigation in Xi’an, and may also guide land subsidence research in other cities.
Highlights
Land subsidence caused by the compaction of aquifer systems is a worldwide engineering and geological problem in urban areas, which are heavily dependent on groundwater supplies
We focus on the surface deformation in Xi’an city with the area of 39 × 44 km2, outlined in Figure 1 by the red rectangle, where severe land subsidence and ground fissures have occurred in past several decades and few new results available after 2012
The stratums related to groundwater exploitation and land subsidence are mainly located above a depth of 300 m, and consist of three layers from top to bottom: Pleistocene loess (15–30 m), Middle-Pleistocene fluvial and lacustrine strata composed of thin silt clay and silt (30–130 m), and thick Lower Pleistocene fluvial strata composed of gravel and cohesive soil interbeds [3]
Summary
Land subsidence caused by the compaction of aquifer systems is a worldwide engineering and geological problem in urban areas, which are heavily dependent on groundwater supplies. The traditional methods provide good precision of measurements and valuable deformation history, they are of limited use in the detection of land subsidence associated with groundwater depletion over large areas, and in retrieving data on the historic evolution of land subsidence and ground fissures, due to the labor-intensive and time-consuming nature of these problems. We focus on the surface deformation in Xi’an city with the area of 39 × 44 km, outlined in Figure 1 by the red rectangle, where severe land subsidence and ground fissures have occurred in past several decades and few new results available after 2012. HTahve eresdueltvs eloped continuaonudsalcyc,uwrachyicvhalipdoatsieons aaresedreisocruibsetdhirneSaetcttioonu4r.bSaonmceoannasltyrsuecstoiof rnegaionndalilnafnrdassutrbusicdteunrcee.aTrehgeirveefnore, the study oifntSheectsiounrf5a.cDeidsceufsosriomnsatairoenpirnovXidi'eadninisSoefctgiornea6t, asnigdnciofniccalundcien.gWreemfaorckus saroengitvheensiunrSfeaccteiodne7f.ormation in Xi’an2.cTithyewGietohlothgiecaalrBeaacokfgr3o9u×nd44ofktmhe2,SotuudtylinAerdeain Figure 1 by the red rectangle, where severe land subsidence and ground fissures have occurred in past several decades and few new results available after 2012.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
