Diagnosing Subsidence Geohazard at Beijing Capital International Airport, from High-Resolution SAR Interferometry
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sustainability Article Diagnosing Subsidence Geohazard at Beijing Capital International Airport, from High-Resolution SAR Interferometry Keren Dai 1,2 , Xianlin Shi 2,*, Jisong Gou 2, Leyin Hu 3, Mi Chen 4, Liang Zhao 5, Xiujun Dong 1 and Zhenhong Li 6 1 State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (Chengdu University of Technology), Chengdu 610059, Sichuan, China; [email protected] (K.D.); [email protected] (X.D.) 2 College of Earth Science, Chengdu University of Technology, Chengdu 610059, Sichuan, China; [email protected] 3 Beijing Earthquake Agency, Beijing 100080, China; [email protected] 4 College of Resources Environment and Tourism, Capital Normal University, Beijing 10048, China; [email protected] 5 College of Geophysics, Chengdu University of Technology, Chengdu 610059, Sichuan, China; [email protected] 6 COMET, School of Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, UK; [email protected] * Correspondence: [email protected] Received: 18 February 2020; Accepted: 11 March 2020; Published: 13 March 2020 Abstract: Beijing Capital International Airport (BCIA) has suffered from uneven land subsidence since 1935, which affects the smoothness of airport runways and seriously threatens the safety of aircrafts. In this paper, a spaceborne interferometric synthetic aperture radar (InSAR) with high-resolution Cosmo-SkyMed SAR data was utilized at BCIA for the first time to diagnose the subsidence hazard. The results show that subsidence is progressing at BCIA at a maximum rate of 50 mm/year, which is mainly distributed in the northwest side of the airport. It was found that the Shunyi-Liangxiang fault directly traverses Runway2 and Runway3 and causes uneven subsidence, controlling the spatial subsidence pattern to some degree. Four driving factors of subsidence were investigated, namely: the over-exploitation of groundwater, active faults, compressible soil thickness, and aquifer types. For the future sustainable development of BCIA, the influence of Beijing new airport and Beijing Daxing International Airport (BDIA), was analyzed and predicted. It is necessary to take relevant measures to control the uneven subsidence during the initial operation of BDIA and conduct long-term monitoring to ensure the regular safe operation of BCIA. This case demonstrates a remote sensing method of diagnosing the subsidence hazard with high accuracy and non-contact, providing a reliable alternative for the geohazard diagnosis of key infrastructures in the future. Keywords: subsidence geohazard; InSAR; Beijing Capital International Airport; geological fault; driving factors 1. Introduction Beijing, the political center of China with a population of more than 21 million, has suffered from land subsidence since 1935 [1]. Severe subsidence still occurs in eastern Beijing, with a maximum subsidence rate exceeding 10 cm/year [2–4]. Beijing Capital International Airport (BCIA) is located in the Beijing Shunyi District, northeast of downtown, which was involved in the core subsidence area in Beijing. The runways in the airport are the infrastructures that most require stable ground [5]. Sustainability 2020, 12, 2269; doi:10.3390/su12062269 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 2269 2 of 16 Significant uneven subsidence or fissure would cause the risk of major disruption. It could particularly pose a great threat to the safety of aircrafts during takeoff, landing and taxing. Monitoring and controlling the subsidence of runways are of great significant to ensure the safe operation of the whole airport and avoid the potential extensive loss of life and property. During the last three decades, interferometric synthetic aperture radar (InSAR) technology has developed into a powerful tool, providing high-resolution, day-and-night, weather-independent wide-coverage and high-accuracy measurements of the earth surface [6]. It has been widely used in various applications, such as the displacements monitoring of city subsidence [7–12], important infrastructures [13–16] and landslides geohazards [17–21]. Compared to traditional geodetic measuring methods—e.g., leveling and global positioning system (GPS)—InSAR measurements do not need any on-site installation and power supply, thus they will not have any impact on the regular operation of the airport. InSAR has been used in several airport subsidence monitoring, such as in Chek Lap Kok Airport [22]. The subsidence in BCIA has been monitored using InSAR technology, which has drawn wide attention from the government and relevant scholars. Gao et al. used multi-temporal InSAR technology to investigate the deformation in BCIA with Envisat ASAR images (from 2003 to 2013) [23] and with TerraSAR-X data (from 2010 to 2017) [24]. Continuous monitoring covering BCIA is in high demand in order to investigate the latest subsidence and to take necessary measures, especially with high-resolution data, resulting in detailed subsidence analysis. In this paper, current land subsidence in BCIA was investigated using time series InSAR technology based on twenty-one high-resolution Cosmo-SkyMed (CSK) SAR images, which were acquired from November 2017 to February 2019. We obtained the latest spatiotemporal subsidence in BCIA with a maximum subsidence rate of 50 mm/year. The 3 m high-resolution CSK data enabled us to analyze the uneven subsidence on each terminal building and runway. Linear subsidence boundaries were found, which corresponded to the geological fault trace. The subsidence and geological fault that affected BCIA was explored. The future sustainable development analysis of BCIA was discussed in detail, combining the subsidence driving factors and the influence of the new airport in Beijing. 2. Study Area, Data Source The Beijing Plain is located in the northern part of the North China Plain, which is formed by sediments carried by Chaobai River and Wenyu River, surrounded by the Yanshan Mountains in the north and the Taihang Mountains in the west. It is a typical piedmont alluvial plain and most of the area is covered by fine sediments (Figure1a). BCIA, located 32 km northeast of Beijing’s city center, is the 4F-level international airport serving Beijing. The airport is located in a flat zone between the Wenyu River and the Chaobai River alluvial fan at the end of the Yongding River alluvial fan, with an average elevation of 30.4 m (Figure1a). It has been the world’s second busiest airport in terms of passenger traffic since 2010. In 2018, the airport handled of 614-thousand air traffic movements, 100 million passengers, and over 2 million tons of cargo in total [24], becoming the second airport in the world with an annual passenger throughput of over 100 million. BCIA was opened in 1958 and three round expansion were performed in 1980, 1999 and 2007. Now there are in total three terminals and three runways within the airport (Figure1b). Terminal 1 (T1) and Terminal 2 (T2), in the west part of the airport linked by a public walkway, were opened on 1980 and 1999 with a floor area 60000 m2 and 336000 m2 [25], respectively. Terminal 3 (T3), opened in 2008, is the largest airport terminal building complex built in a single phase, with 986,000 m2 in total floor area, consisting of a main passenger terminal (Terminal 3C, T3C), two satellite concourses (Terminal 3D and Terminal 3E, T3D and T3E), and five floors above ground and two underground [25] (Figure1b). There are, in total, three runways in the BCIA. All of them have the same geographic bearing and magnetic bearing of 173/353◦ and 179/359◦, respectively [24]. The dimensions of Runway2 and Runway3 are 3800 60 m and 3200 50 m for Runway1. × × Sustainability 2020, 12, 2269 3 of 16 Sustainability 2020, 12, x FOR PEER REVIEW 3 of 17 Figure 1. (a) GeologicalGeological settings and locationlocation of Beijing and BCIA;BCIA; ((b)) DistributionDistribution of terminalsterminals andand runways in BCIA. CSKBCIA is was an Earth-observation opened in 1958 and satellite three space-based round expa radarnsion systemwere performed funded by in the 1980, Italian 1999 and and Ministry 2007. ofNow Defence there (MoD),are in total controlled three andterminals maintained and three by the runways Italian Spacewithin Agency the airport (ASI), (Figure intending 1b). for Terminal Dual-use 1 (both(T1) and military Terminal and 2 civilian (T2), in use)the west to establish part of the a global airport service linked supplyingby a public provision walkway, of were SAR opened data [26 on]. The1980 spaceand 1999 segment with ofa floor the system area 60000 includes m2 and a constellation 336000 m2 [25], of four respectively. mid-sized Terminal satellites and3 (T3), each opened of them in was2008, equipped is the largest with airport a multi-mode terminal high-resolution building complex SAR built operating in a single at X-band phase, with with global 986,000 coverage m2 in total [27]. Eachfloor satellitearea, consisting repeats theof a same main ground passenger track terminal every 16 (Terminal days, and 3C, allof T3C), thesatellites two satellite follow concourses the same ground(Terminal track 3D ofand between Terminal 1 and 3E, 15T3D days and [ 26T3E),], providing and five observationfloors above ofground an area and of interesttwo underground with 1–16 repeated[25] (Figure cycle 1b). in There all-weather are, in conditions.total, three runways The CSK in satellites the BCIA. have All three of them basic have types the of same imaging geographic modes, namelybearing Spotlightand magnetic mode, bearing Stripmap of mode, 173/353° ScanSAR and mode.179/359°, respectively [24]. The dimensions of Runway2In this and study, Runway3 twenty-one are 3800 CSK × images60 m and were 3200 acquired × 50 m for during Runway1. November 2017 to March 2019 with descendingCSK is orbitan Earth-observation in Stripmap mode. satellite The images space-based are single radar polarization system (HH) funded data by in SLCthe (singleItalian lookand complex)Ministry of format, Defence with (MoD), a spatial controlled resolution and of maintain 3 m and aned incidentby the Italian angle ofSpace 20.1 ◦Agency.