佛山地铁沿线时序InSAR形变时空特征分析

佛山作为中国珠三角地区经济和城市化高速发展的城市,由于其脆弱的地质水文条件,长期遭受地面沉降灾害的影响。同时,该区域地铁作为缓解城市交通压力的重要工具,其施工和运行所导致的地面沉降也影响了人们的生命财产安全。但目前针对佛山地区相关的系统研究不多,对地铁沿线的沉降规律认识不足。利用Sentinel-1数据监测了2015-06至2018-09间佛山市的形变信息,结果表明,佛山市地表形变呈零星分布,未出现大范围的沉降漏斗,形变速率为-20~5 mm/a,局部区域的沉降速率超过-30 mm/a。地面沉降主要与不稳定的地质结构、地下水抽取和局部区域工程施工有关。基于获得的形变结果,对佛山市地铁沿线的形变情况进行了研究,并对2018年佛山市地铁坍塌事故路段的沉降情况进行了详细分析,阐述了在空间分布上地铁沿线沉降差异的成因,并在时间上对地铁沿线的形变进行了模型参数反演。研究工作为今后当地政府开展地表形变普查、沉降灾害预警提供了参考,并为地铁正常运行与维护的安全监测提供了理论依据。     

Temporal and Spatial Evolution of Land Subsidence Induced by Groundwater Exploitation and Construction in the Eastern Chaoyang District,Beijing, China

Human activities have a large impact on land subsidence in great metropolitan areas. In this study, the RADARSAT-2 observation data over a 4-year period (from November 2010 to September 2014) is used to investigate the trends of land subsidence in the eastern Chaoyang District in Beijing, China, and to analyze the impact of human activities on it. The observation results indicate that the temporal and spatial evolutions trend of land subsidence in this area is uneven, with deformation rates ranging from ??116.52 to 7.1 mm/year. There are two large subsidence areas located in the northern part of the study area, and we find that the groundwater exploitation and deformation rates are strongly linearly correlated. The effect of construction on land subsidence has also been investigated. Over time, land subsidence is generally increased in the study area, with an exception at the Longfor Changying Galleria area, which is under construction during the observation period. Based on the time-series analysis of permanent scattered points in the 200 m buffer area, construction activities are observed to cause both land subsidence and upheaval deformation of the surrounding soil. During the construction period, the displacement of the surrounding soil is disturbed. After completion, the initial displacement of surrounding soil is tended to involve the uplift of the surrounding soil, followed by a gradual subsidence with time.     

InSAR填海区地铁沿线地表沉降反演分析

为了更好地监测和掌握深圳填海区地铁工程结束后地铁沿线的地面沉降情况,该文利用TS-InSAR技术和20景2017年8月15日—2019年3月14日的Sentinel-1A SAR数据,借助POD精密定轨星历和ASTER GDEM V2分别去除轨道误差和地形相位,反演了深圳填海区2017—2019年地表沉降时间序列,并在此基础上重点分析了填海区地铁沿线地面沉降的时空演变规律以及地面沉降成因。结果显示,填海区各地铁沿线的地面沉降特征较为明显,最大沉降速率为-17.52 mm/a。其中,宝安中心、前海湾、深圳湾区段地铁沿线的地面沉降趋势较为严重,其地面沉降呈现逐渐增强和扩散趋势。     

PSP-InSAR技术在地铁沿线的形变监测应用

基于56景COSMO-SkyMed影像,本文采用PSP-InSAR技术对杭州地铁2号线沿线500 m范围进行地面沉降监测,并对形变区的位置、面积和数量进行了统计,在此基础上提取形变梯度大于0.1 mm/m的累计形变量点并开展比对分析。结果表明：①虽然地表形变集中区、形变严重区和形变梯度较大区域有着高度的重叠,但部分形变集中区内形变量和形变梯度并不大,也存在形变平稳区段形变梯度却较为显著现象,因此单从一个角度分析地铁沿线的形变,易增加漏检和错检的概率。②PSP-InSAR技术可从空间上完整表现地铁线上沉降的分布特征,对于地铁竣工运营期间的沉降监测具有显著意义,可为地铁的运营维护提供依据。     

Change in regional land subsidence in Beijing after south-to-north water diversion project observed using satellite radar interferometry

ABSTRACT

Over-exploitation of groundwater has caused severe land subsidence in Beijing during the past two decades. Since the middle route of South-to-North Water Diversion Project (SNWDP), the biggest water diversion project in China, started to deliver water to Beijing in December 2014, the groundwater shortage has been greatly alleviated. This study aims to analyze the impact of SNWDP on the spatiotemporal evolution of land subsidence in Beijing. Change in surface displacement in Beijing after SNWDP was retrieved and the spatiotemporal patterns of the change were analyzed based on long time-series Envisat Advanced Synthetic Aperture Radar (ASAR) (2004–2010), Radarsat-2 (2011–2014), and Sentinel-1 (2015–2017) satellite datasets using Permanent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) techniques. Land subsidence unevenness index (LSUI) was proposed to represent the spatial unevenness of surface displacement. PS-Time approach was then adapted to examine the time series evolution of LSUI. The results showed that the InSAR measurements agree well with leveling measurements with R² over 0.96. Although the maximum annual displacement rate reached ?159.7 mm/year by 2017, over 57% of the area within 25 mm/year contour line showed decreasing or unchanged displacement rate after the south-north water delivered to Beijing. The settlement rate in Chaoyang-Dongbalizhuang (CD) subsidence center has decreased for 26 mm/year from 2011–2014 to 2015–2017. Only around 15% of the area experienced continued accelerating settlement rate through the three time periods, which was mainly located in the area with the compressible layer thickness over 190 m, while the magnitude of velocity increment considerably decreased after SNWDP. Land subsidence unevenness, represented by LSUI, developed more slowly after SNWDP than that during 2011–2014. However, LSUI at the edge of settlement funnel has kept developing and reached 1.7‰ in 2017. Decreasing groundwater level decline after SNWDP and the positive relationship (R² > 0.74) between land subsidence and groundwater level clearly showed impacts of SNWDP on the alleviating land subsidence. Other reasons include geological background, increasing precipitation, and strict water management policies implemented during these years.     

Land subsidence prediction in Beijing based on PS-InSAR technique and improved Grey-Markov model

Land subsidence induced by excessive groundwater withdrawal has caused serious social, geological, and environmental problems in Beijing. Rapid increases in population and economic development have aggravated the situation. Monitoring and prediction of ground settlement is important to mitigate these hazards. In this study, we combined persistent-scatterer interferometric synthetic aperture radar with Grey system theory to monitor and predict land subsidence in the Beijing plain. Land subsidence during 2003–2014 was determined based on 39 ENVISAT advanced synthetic aperture radar (ASAR) images and 27 RadarSat-2 images. Results were consistent with global positioning system, leveling measurements at the point level and TerraSAR-X subsidence maps at the regional level. The average deformation rate in the line-of-sight was from ?124 to 7 mm/year. To predict future subsidence, the time-series deformation was used to build a prediction model based on an improved Grey-Markov model (IGMM), which adapted the conventional GM(1,1) model by utilizing rolling mechanism and integrating a k-means clustering method in Markov-chain state interval partitioning. Evaluation of the IGMM at both point level and regional scale showed good accuracy (root-mean-square error <3 mm; R² = 0.94 and 0.91). Finally, land subsidence in 2015–2016 was predicted, and the maximum cumulative deformation will reach 1717 mm by the end of 2016. The promising results indicate that this method can be used as an alternative to the conventional numerical and empirical models for short-term prediction when there is lack of detailed geological or hydraulic information.     

Land subsidence under different land use in the eastern Beijing plain,China 2005-2013 revealed by InSAR timeseries analysis

Land subsidence has been occurring in Beijing since the 1970s. Five major land subsidence areas have been formed: Dongbalizhuang–Dajiaoting, Laiguangying, Changping Shahe–Ba Xianzhuang, Daxing Yufa–Lixian, and Shunyi–Ping Gezhuang. In this paper, we studied on land subsidence in Dongbalizhuang–Dajiaoting and Laiguangying using small baseline subset interferometry and interferometric point target methods of 47 ENVISAT ASAR and 29 RADARSAT-2 data. The results showed that the degree of land subsidence in these areas varied significantly. The mean land subsidence rate ranged from 143.43 to 8.2 mm/a and from 132.11 to 7.3 mm/a during 2005–2010 and 2011–2013, respectively. We correlated the observed settlement with the land use (agricultural, residential, and industrial). Displacement in the agricultural areas was greater than that in the other areas from 2005 to 2013. Moreover, we compared the observed deformation and the groundwater level in phreatic and confined aquifers. There was a strong correlation between ground subsidence and the groundwater level and the ground settlement increased with a decrease in the groundwater level and the maximum correlation coefficient can reach 0.525. Furthermore, subsidence appeared to be associated with compressible deposits, suggesting that for 90–210-m thick compressible deposits, ground settlement is more likely to occur as the thickness of the compressible layer increases.     

基于PS-InSAR的京津城际铁路地面沉降监测研究

合成孔径雷达干涉测量技术可以大范围监测地表形变,对高速铁路运行沿线具有较好的监测能力。本文以ENVISATASAR数据为基础,采用PS—InSAR监测北京和天津地区的地面沉降的特征,通过临轨基准转换完成了两个区域的拼接,实现了在同一基准上的大尺度京津城际铁路沿线地面沉降的监测。通过本次研究,我们掌握了京津城际铁路沿线地面沉降的分布,以典型区域为样方分析其时间序列演化特征,并分析城际铁路不均匀地面沉降的运行风险。     

厦门岛地表沉降监测SBAS-In SAR技术研究

伴随着城市建设不断发展,尤其是地铁项目的建设,城市地区地表沉降、塌陷等地质灾害频繁发生,给经济建设和人民的生命财产安全带来了不可估量的损失,大范围的沉降监测成为目前一个亟待解决的问题。本文通过获取的厦门岛16个时间序列InSAR影像数据,分析厦门岛的地面沉降率,从而提出厦门岛的筼筜外湖,地铁1号线的中山公园—将军祠—文灶—湖滨东路路段以北地区,以及湖边水库周边可能会持续产生地面沉降,应及早做好地质灾害预防。     

利用时序InSAR监测兰州市中心城区地面沉降

针对兰州市中心城区的地面沉降问题,该文采用PS-SBAS和PS-InSAR技术,利用2016-01-20—2019-02-21时间段内的39景Sentinel-1A/B降轨数据,使用缓冲区分析技术对兰州市中心城区轨道交通线和铁路线周边100m区域做了沉降影响分析,监测结果表明:基于Sentinel-1A/B数据和时序InSAR技术,可以准确监测城市地表的沉降和轨道交通线的沉降时空规律;沉降区域主要集中在研究区东南部的方家泉村、和平镇和猪咀岭村;软土地基下地铁的施工会导致沉降现象的发生,兰州轨道交通线和铁路线的沉降主要发生在城区东南方向;在监测时段内,使用两种时序InSAR技术监测的同名点在沉降趋势和累计沉降量上保持了良好的一致性和吻合性,但PS-InSAR的时序变化曲线较PS-SBAS更为平缓。     

北京市地铁暗挖施工沉降控制探讨

仅以北京市地铁4#线张自忠车站主体暗挖施工的沉降监控项目为研究背景,对穿越城市主干道的车站结构暗挖施工进行连续性的沉降变形监测;从地下构筑物暗挖施工的工序变化与地表沉降的关系进行试验研究.在预测基础上对获取的数据进行多层次的统计与分析,以研究其变形规律与稳定性,实现了信息化施工.     

空地地一体化的全方位准动态地铁施工安全监测技术

鉴于软土地区土性的极端复杂和地面沉降严重的普遍特征,提出了“空（天空）～地（地面）～地（地下）”一体化的全方位准动态地铁施工安全监测思想,构建起了相应的技术体系（即全方位准动态集成技术）。软土地区地铁施工安全监测全方位准动态集成技术的核心是借助GPS技术建立三维的空基变形监测基准（用于地表变形监测和地下变形监测。该空基变形监测基准可以克服传统陆基基准因软土地区地面沉降而对变形监测数据产生的系统性偏差,还可实现地铁施工变形监测的全天候、实时化与动态化）,以城市基础地质资料库作为安全监测整体性设计的依据（提高了地铁施工安全监测的针对性、可靠性与有效性）,以准实时、准动态的地下结构应力应变监测结果作为施工安全性的重要判别要素,以准实时、准动态的地面变形监测结果作为地铁施工作用下城市环境安全性的关键判别要素,实现对地铁施工安全的全方位、实时化、准动态控制。     

时空三维相位解缠算法改进研究

三维相位解缠是时序干涉合成孔径雷达（interferometric synthetic aperture radar,InSAR）技术的关键环节之一,解缠结果直接影响时序InSAR地面沉降监测的精度。针对地面沉降严重、地形坡度变化较大的区域,因相位欠采样引起的整周期解缠误差问题,提出了一种基于频域置信度的加权最小二乘相位解缠算法,并以此替代时空三维相位解缠中空间维以相位梯度为权重的加权最小二乘相位解缠算法。通过提高相位坡度变化估计的准确性,进而提高时空三维相位解缠的精度和稳定性。以北京地区地面沉降监测为例进行了验证,结果表明,与经典的时空三维相位解缠算法相比,改进算法得到的沉降监测结果精度更高,特别是对于坡度变化较大、失相干现象明显的沉降漏斗区,其沉降监测精度有明显改善。     

南京地铁沿线地面沉降监测与危险性评价

采用MCTSB-InSAR技术监测南京市主城区地面沉降状况,揭示研究区内地面沉降空间分布特征;通过对地铁线路进行条带空间缓冲区分析和沿线路剖面线分析,进一步研究地铁沿线的地面及周边建筑物不均匀沉降信息;针对主要影响路段进行地质灾害危险性评价,评价结果及特征点时间序列沉降结果与同时期实际情况基本吻合。研究表明,长期进行城市主城区及地铁线路地面沉降监测具有重要意义,同时地质灾害危险性评价工作能为灾害防治及评估提供可靠的支持,具有较大的应用潜力。     

高速铁路沉降评估中工程沉降和区域沉降的可区分性研究

某高速铁路北京至济南段地处华北平原,沿线经过的大部分地区都存在着不同程度的地面沉降。对穿越不同地面沉降速率区段的高速铁路工程,沉降观测得到的桥墩沉降量是工程沉降与区域沉降的综合体现。由于地面沉降速率在空间上是不均匀的,本文对区分工程沉降和区域沉降进行了研究,并提出了对沉降观测的改进措施。     

利用PS-InSAR技术进行城市地铁沿线形变监测与机理分析

本文利用PS-InSAR技术获取了上海地区沉降速率场及累计沉降量等信息,并分析了该地区的沉降时空分布特征,以及该地区沉降与降水量、地铁施工运营等因素之间的关系。研究表明:①上海市沉降呈不均匀分布,北部沉降较稳定,而中部的虹口区、南部的闵行区、东部的浦东新区均发生了不同程度的沉降。其中,闵行区沉降最为严重,其最大累计沉降量达-43 mm,呈大范围、大沉降现象。②研究区域内沉降量呈非线性沉降现象及明显的季节性变化,且与地区降水量有关,降雨量对地下水的及时补充可以有效缓解地面过度沉降的发生。③上海地铁3、15、16号线部分路段均出现明显沉降现象,且处于在建阶段的15号线沉降最为明显,部分路段最大累计沉降量达-34 mm。     

Subsidence in the Kathmandu Basin,before and after the 2015 Mw 7.8 Gorkha Earthquake,Nepal Revealed from Small Baseline Subset-DInSAR Analysis

Land subsidence in densely urbanized areas is a global problem that is primarily caused by excessive groundwater withdrawal. The Kathmandu Basin is one such area where subsidence due to groundwater depletion has been a major problem in recent years. Moreover, on 25 April 2015, this basin experienced large crustal movements caused by the Gorkha earthquake (Mw 7.8). Consequently, the effects of earthquake-induced deformation could affect the temporal and spatial nature of anthropogenic subsidence in the basin. However, this effect has not yet been fully studied. In this paper, we applied the SBAS-DInSAR technique to estimate the spatiotemporal displacement of land subsidence in the Kathmandu Basin before and after the Gorkha earthquake, using 16 ALOS-1 Phased Array L-band Synthetic Aperture Radar (PALSAR) images during the pre-seismic period and 26 Sentinel-1 A/B SAR images during the pre- and post-seismic periods. The results showed that the mean subsidence rate in the central part of the basin was about ?8.2 cm/year before the earthquake. The spatial extents of the subsiding areas were well-correlated with the spatial distributions of the compressible clay layers in the basin. We infer from time-series InSAR analysis that subsidence in the Kathmandu basin could be associated with fluvio-lacustrine (clay) deposits and local hydrogeological conditions. However, after the mainshock, the subsidence rate significantly increased to ?15 and ?12 cm/year during early post-seismic (108 days) and post-seismic (2015–2016) period, respectively. Based on a spatial analysis of the subsidence rate map, the entire basin uplifted during the co-seismic period has started to subside and become stable during the early-post-seismic period. This is because of the elastic rebound of co-seismic deformation. However, interestingly, the localized areas show increased subsidence rates during both the early-post- and post-seismic periods. Therefore, we believe that the large co-seismic deformation experienced in this basin might induce the local subsidence to increase in rate, caused by oscillations of the water table level in the clay layer.     

利用TPCA分析北京平原区地面沉降的时空演化特征

时间主成分分析（temporal principal component analysis,TPCA）可用于地学领域中提取时空数据的时序特征和空间分布特征,北京平原区的地面沉降具有典型的时序和空间特征。在利用永久散射体干涉测量技术获取的北京平原区2003—2010年地面沉降数据的基础上,采用TPCA方法分析了北京平原区地面沉降时空演化特征。经分析发现:（1）TPCA分析得到的第一主成分反映了地面沉降在该长时序阶段的空间分布特征。（2）第二主成分得分为正的空间点与可压缩层厚度在130 m以上的区域在空间分布上有一致性和相关性。（3）在空间上,第一主成分为负值与第二主成分为正值的永久散射体点分布在年均沉降速率30 mm/a以上的严重沉降区域。严重沉降区具有明显的南北沉降分类现象和季节性差异,具体表现为:北部沉降区在春夏季节的沉降量大于秋冬季节;南部沉降区则与之相反。总之,基于时间主成分分析方法可分析得到研究区的地面沉降时空演化规律,为城市安全监测提供数据支撑。     

Interferometric SAR Time Series Analysis for Ground Subsidence of the Abandoned Mining Area in North Peixian Using Sentinel-1A TOPS Data

The North Peixian mining area of China has rich coal resources, with total proven reserves of 2.37 billion tons. However, the underground coal mining activities have resulted in ground collapse, which has caused serious harm to the environment and threatened the lives and properties of local residents. In this study, 12 Sentinel-1A terrain observation by progressive scans (TOPS) mode acquisitions between 30 July 2015 and 13 May 2016 over the abandoned mining area in North Peixian were analyzed using the interferometric synthetic aperture radar (InSAR) time series method to detect the ground subsidence, with the maximum ground subsidence reaching 83 mm/a and an average value of about 12.7 mm/a. The subsidence results derived from the Sentinel-1A TOPS mode dataset were proven to be effective in investigating and monitoring the ground subsidence in the North Peixian mining area. Compared to the rapid deformation during the ongoing period of mining excavation, the ground subsides slowly in abandoned mining areas and shows a linear relationship with time over a relatively long period of time. Spatial correlation between the subsidence distribution and land cover was found, in that the magnitude of the subsidence in urban areas was smaller than that in rural areas, which is associated with the controlled coal mining activities under buildings, railways, and water bodies. The results demonstrate that Sentinel-1A TOPS SAR images can be used to effectively and accurately detect and monitor ground subsidence in a mining area, which is critically important when investigating land subsidence in a large-scale mining area.     

区域沉降对城市轨道交通建设的影响及应对措施

当轨道交通穿越沉降漏斗区和沉降带时,会对城市轨道交通线路的建设及运营产生非常大的破坏影响。为使测量技术更好地为城市轨道交通工程建设服务,本文以北京地铁14号线工程建设的实际测量作业为背景,通过分析、研究与总结,从高程贯通误差公式设计依据、地面沉降对高程贯通误差的影响、考虑地面沉降的高程贯通误差计算、建设阶段实际地面沉降影响及应对措施等几个部分进行阐述。区域沉降对城市轨道交通建设的影响及应对措施是在工程实践中通过研究分析得出的成果,对今后我国各城市的城市轨道交通工程建设的测量具有参考和指导意义。