SBAS-InSAR Based Deformation Detection of Urban Land, Created from Mega-Scale Mountain Excavating and Valley Filling in the Loess Plateau: The Case Study of Yan’an City

Abstract

Yan'an new district (YND) is one of the largest civil engineering projects for land creation in Loess Plateau, of which the amount of earthwork exceeds 600 million m 3 , to create 78.5 km 2 of flat land. Such mega-scale engineering activities and complex geological characteristics have induced wide land deformation in the region. Small baseline subset synthetic aperture radar interferometry (SBAS-InSAR) method and 55 Sentinel-1A (S-1A) images were utilized in the present work to investigate the urban surface deformation in the Yan'an urban area and Yan'an new airport (YNA) from 2015 to 2019. The results were validated by the ground leveling measurements in the YNA. It is found that significant uneven surface deformation existed in both YND and YNA areas with maximum accumulative subsidence of 300 and 217 mm, respectively. Moreover, the average subsidence rate of the YND and YNA areas ranged from −70 to 30 mm/year and −50 to 25 mm/year, respectively. The present work shows that the land deformation suffered two periods (from 2015 to 2017 and from 2017 to 2019) and expanded from urban center to surrounding resettlement area, which are highly relevant with urban earthwork process. It is found that more than 60% of land subsidence occurs at filled areas, while more than 65% of surface uplifting occurs at excavation areas. The present work shows that the subsidence originates from the earth filling and the load of urban buildings, while the release of stress is the major factor for the land uplift. Moreover, it is found that the collapsibility of loess and concentrated precipitation deteriorates the degree of local land subsidence. The deformation discovered by this paper shows that the city may suffer a long period of subsidence, and huge challenges may exist in the period of urban maintaining buildings and infrastructure facilities.The widely applied methods for monitoring urban surface deformation are leveling measurement and global navigation satellite system (GNSS) measurement [17]. These methods can achieve high precision at single points in the monitoring of local land subsidence with low spatial resolution and high cost [18]. On the other hand, synthetic aperture radar interferometry (InSAR) has significant advantages over other methods, including fast surface deformation with large monitoring range, operability in all climatic conditions, low operational cost and high spatial resolution [19]. The first application of the InSAR was the monitoring of an earthquake in Landers, California [20], but the temporal resolution was relatively low because of the absence of analyzing on time series images. To overcome this limitation, multi-temporal InSAR was introduced for long-term and large-scale monitoring of surface deformation [21,22]. More specifically, a permanent scatterers InSAR (PS-InSAR) method proposed by Ferretti et al. and a small baseline subset InSAR (SBAS-InSAR) method introduced by Berardino et al. have been widely used in related fields with millimetric accuracy [23][24][25]. Zhang and Zhou analyzed W...

Characterizing the Topographic Changes and Land Subsidence Associated with the Mountain Excavation and City Construction on the Chinese Loess Plateau

“…The narrow and long urban area of approximately 36 km 2 accommodates nearly 500,000 people, making the local construction land per capita far below the national standard for land utilization. Simultaneously, Yan'an city, as a revolutionary holy land of China, has over 140 historical relics [5]. However, in order to obtain more land for urban development, a large number of revolutionary sites have been occupied and destroyed, which intensified the competition between urban and landscape areas.…”

Characteristics of Surface Deformation in Lanzhou with Sentinel-1A TOPS

“…Rock masses with considerable water content are weak, and they show plastic failure and have low shear strength [30]. It is well-known that loess has collapsibility [33,34]; therefore, surface deformation was seen in Region P2. In Region P3, the geology is part of the Hekou Group and the Upper Pleistocene Aeolian Group, which consist of materials such as sandstone, conglomerate, glutenite, argillaceous siltstone, mudstone and loess.…”

Ground Deformation of the Chongming East Shoal Reclamation Area in Shanghai Based on SBAS-InSAR and Laboratory Tests

“…When generating ground deformation, one hundred and twenty-five ground control points (GCPs) that approved the quality inspection were utilized in the area to the west of the G40 expressway in order to eliminate the change of phase caused by satellite orbit errors and remove the residual topographic phase. An atmosphere high path size of 365 days and an atmosphere low path size of 1200 days were utilized to alleviate the atmosphere delay [53].…”