Surface deformation monitoring is the basic work of geological disaster prevention and early warning. At present, frequent landslides, land subsidence, ground fissures and land subsidence in China have gradually increased the threat to human settlements. The traditional ground survey method is limited by the shortcomings of small monitoring range, low point density and long survey period, and its monitoring ability on the macroscopic characteristics and temporal and spatial evolution of geological disasters is limited. Since the end of 1990s, synthetic aperture radar interferometry has been widely studied and applied in all kinds of surface deformation monitoring, which has the advantages of rapidity, accuracy, high precision and wide coverage, and has changed the shortcomings of previous measurement methods, such as low point density, long working period and high measurement requirements.
The core of InSAR technology is to obtain the geometric characteristics and change information of the target by using phase observations. Because the interference phase is extremely sensitive to small deformation, the deformation of millimeter level will be reflected in the interference phase, so high-precision deformation information can be obtained by differential interference processing using the interference phase obtained from repeated orbit observation.
Since 2000, with the support of the Ministry of Land and Resources, the Ministry of Science and Technology and other departments, the Space Center has carried out research on the theory, method and application of InSAR technology, relying on the general survey of land and resources, the public welfare industry fund of the Ministry of Land and Resources, the 863 Program and other projects, and formed a multi-scale and multi-type InSAR survey and monitoring technology system that tends to be perfect. Through InSAR key technology research, application demonstration, results verification and engineering application, a series of key technologies of land deformation monitoring engineering application such as land subsidence information extraction, cross-track, multi-map and large-scale land subsidence monitoring mapping under the condition of low coherence and limited data volume are systematically solved, and a set of InSAR method technical system is established to solve the synchronous monitoring of land subsidence in large areas. For the first time in China, InSAR technology is systematically used to carry out large-scale regional land subsidence engineering monitoring, and the full coverage and high-precision land subsidence monitoring data of North China Plain, Yangtze River Delta and Wei Fen River Basin are obtained, which fills the gap in the basic land subsidence survey data. The engineering application shows that the accuracy of InSAR time series technology for coherent targets is better than 3 ~ 5 mm, and the regional monitoring population variance is better than 65438±0cm, which meets the needs of land subsidence monitoring. The research and application of InSAR technology has improved the working ability and technical level of land deformation monitoring, especially regional land subsidence monitoring in China, and achieved remarkable social and economic benefits.
Second, the scope of application and application examples
The research results have been applied to various types of ground deformation monitoring, such as ground subsidence, landslide, high-speed rail subsidence, oil field ground deformation and mining subsidence. Since 2004, InSAR engineering monitoring has been carried out in North China Plain, Yangtze River Delta and Wei Fen River Basin, which has broken through the limitation of land subsidence monitoring by independent administrative divisions in the past, achieved "one map" of regional land subsidence monitoring results, and filled the blank of basic data of land subsidence prevention and risk management in China.
At the same time, in view of the requirements of major projects for ground stability, InSAR investigation and monitoring of land subsidence in a number of major engineering areas, such as Beijing-Tianjin, Beijing-Shanghai high-speed railway, the east route of South-to-North Water Transfer Project and the Yangtze River Delta section of West-to-East Gas Transmission Project, have been carried out, providing effective technical services for geological disaster risk management in major engineering areas. Application of multi-scale and multi-type surface deformation monitoring such as landslides in the Three Gorges reservoir area (Xintan, Shuping, etc.). ), coal mining subsidence (Tangshan, Yanzhou, etc. ), oilfield ground deformation (Dagang, Dongying, etc. ), urban ground fissures (Xi 'an) and earthquake deformation fields have been developed one after another, which has comprehensively improved the application ability and level of InSAR technology.
Figure 1 InSAR Monitoring Settlement Rate Diagram of Land Subsidence Area in North China Plain (2008 ~ 20 10)
1. Realize the full coverage of the three major land subsidence areas in China.
Using InSAR technology, large-scale and regional land subsidence survey and monitoring were carried out in North China Plain, Yangtze River Delta and Wei Fen River Basin, and the cumulative range exceeded 20× 104 km2, which realized the full coverage of InSAR monitoring in the three major subsidence areas in China for the first time.
(1) InSAR monitoring results of land subsidence in North China Plain
The monitoring range is 14× 104 km2, covering Beijing, Tianjin, Shijiazhuang, Tangshan, Zhengzhou and other cities and the Yellow River Delta (Figure 1). The monitoring results show that since 2004, the urban subsidence rate of major cities (Tianjin, Beijing (Figure 2, Figure 3), Cangzhou, etc.) with serious land subsidence in North China Plain. ) has slowed down, generally less than 30mm；; The main settlement centers are mostly concentrated around these cities, mainly in various development zones. The annual settlement rate of the settlement center is generally greater than 40 ~ 50 mm, and it has a trend of continuous expansion; The settlement area at the junction of provincial administrative regions presents a trend of contiguous development, with a large settlement rate and a wide range; Settlement centers are closely related to the distribution of large-scale infrastructure (railways and highways) and regional economic development.
Figure 2 Cumulative settlement in Beijing from 2007 to 20 10.
Figure 3 Cumulative settlement in Laiguangying, Beijing
(2) InSAR monitoring results of land subsidence in the Yangtze River Delta.
The monitoring area is about 6× 104km2, covering Shanghai (Figures 4 and 5), Suzhou-Wuxi-Changzhou, Jiangsu and Yangtaitong in Hangjiahu, Zhejiang. The distribution of land subsidence in various regions since 2006 has been ascertained, and the continuous monitoring data of Shanghai, Suzhou, Wuxi and Changzhou and Hangjiahu areas have been obtained. It has been found that there are many rapid and large-scale subsidence areas such as Jinshan and Pinghu in the border area of Shanghai and Zhejiang, with the annual maximum subsidence rate of 40. The monitoring shows that the overall subsidence in the Yangtze River Delta is smaller than that in the North China Plain, while the overall subsidence in rate of land subsidence is slowing down, and the rapid subsidence area is still concentrated in the main development zones in China.
Figure 4 Cumulative land subsidence monitored by Shanghai InSAR (September 20, 200310)
Figure 5 Cumulative settlement of Huacao Town (September 20, 200310)
(3) InSAR monitoring results of land subsidence in Wei Fen area.
Fig. 6 rate of land subsidence map of Taiyuan basin (2007 ~ 20 10).
Taking Datong-Taiyuan-Linfen area (Figure 6) and Xi 'an as the main working areas, the development and distribution of land subsidence covering nearly 4× 104 km2 in Wei Fen area were found, and the rapid subsidence areas such as Yuci, Qingxu and Linfen were newly discovered, with the maximum annual subsidence rate of 50 ~ 70mm. The continuous monitoring of land subsidence process in Taiyuan City since 2005 (Figure 7) has been completed, and the temporal and spatial variation characteristics of main subsidence centers have been found out in detail.
Figure 7 Distribution map of main residential areas in the main urban area of Taiyuan City
2. Effectively serve the national major infrastructure construction along the high-speed rail.
Actively serve the construction of major national infrastructure, and apply InSAR technology to carry out land subsidence monitoring and investigation along high-speed railways. Using ESA ENVISAT satellite SAR data (resolution of 20m), the InSAR survey and monitoring of land subsidence along the Beijing-Tianjin high-speed railway were carried out for the first time in China, and the monitoring results of land subsidence from 2004 to now were obtained within 5 km along the line, and two main subsidence funnels in Beijing and Tianjin were found along the Beijing-Tianjin high-speed railway (Figures 8 and 9). At the same time, the German TerraSAR-X high-resolution SAR data (resolution 3m) was used for the first time to carry out fine monitoring of key subsidence areas along the Beijing-Tianjin high-speed railway, and the continuous monitoring data from February 2009 to 10 were obtained, which effectively served the railway department to evaluate the stability of the Beijing-Tianjin high-speed railway foundation and study the countermeasures.
3. Actively carry out various geological disaster monitoring and engineering practice.
On the basis of InSAR monitoring of regional land subsidence, the multi-scale and multi-form detection and monitoring of disastrous ground deformation field, such as mining subsidence investigation, oil field ground deformation monitoring, landslide activity monitoring, urban ground fissure detection and earthquake deformation field extraction, have been carried out, and good results have been achieved. Taking Tangshan Kailuan mining area as the research area (Figure 10 and Figure 1 1), the InSAR monitoring of mining subsidence in coal mining area and ground stability of mining cities is carried out, which proves that InSAR technology can find the mining scope and intensity in time and meet the needs of dynamic monitoring of mining subsidence. At present, it has been widely used in Datong, Yanzhou, Huainan, Xuzhou, northern Anhui and other major coal mining areas. The continuous monitoring of the activity changes of Xintan landslide and Lianziya landslide in the Three Gorges area since 2002 shows that Xintan landslide has stabilized. The ground deformation caused by oil exploitation was monitored by InSAR, and the ground subsidence and uplift in Daqing and Dongying oilfields were found out.
Figure 8 rate of land subsidence map of Beijing-Tianjin high-speed railway (2007-2009)
Fig. 9 Profile of land subsidence along Beijing-Tianjin high-speed railway from 2007 to 2009.
Figure 10 InSAR Interferogram of Mining Subsidence in Kailuan Mining Area (June 7, 2009 to June 36, 2009)
The application of InSAR technology in monitoring the main land subsidence areas and various ground deformation disasters in China shows its unique advantages in the field of geological disaster monitoring. During the Twelfth Five-Year Plan period, InSAR technology will play an important role in the investigation of geological disaster-prone areas, the construction of important economic zones (urban agglomerations), the monitoring of major mineral resources development zones, the monitoring of major groundwater development and utilization zones, and the monitoring of slow surface deformation in major engineering areas. Based on the national regional land subsidence monitoring, focusing on the national major infrastructure construction, relying on InSAR technology to carry out large-scale land deformation monitoring, provide ground stability monitoring and risk assessment, and serve the project planning, construction and operation. The application in mining, petroleum, water conservancy and other fields, especially the monitoring of mining subsidence in coal mining areas and land subsidence in industrial and mining cities, has obvious demand, which will promote InSAR technology to become a daily monitoring means.
Figure 1 1 slow subsidence rate diagram of Tangshan old goaf (2004 ~ 2009)
The development of high-resolution radar satellites and related technologies will further promote the accurate monitoring of geological disasters by InSAR. TerraSAR-X, Cosmo-skymed and other new generation high-resolution radar satellites will provide rich data sources for the refined application of InSAR technology. It will become a reality to use high-resolution SAR data to finely monitor major projects and infrastructure such as high-speed railways, highways, dams and large single buildings. It will play a more important role in the investigation and monitoring of geological disasters in land resources, mines, transportation, water conservancy projects and many other fields.
Third, promote the transformation mode.
The research results have been applied in the planning projects such as monitoring and prevention of land subsidence in North China Plain, monitoring and risk management of land subsidence in Yangtze River Delta, monitoring and prevention of land subsidence in China, etc., and the national remote sensing geological survey of land subsidence was carried out on 20 1 1. The purpose of this paper is to investigate and monitor the land subsidence and mining subsidence in the plains, basins, deltas and coastal areas in central and eastern China by using InSAR technology, to find out the present situation of land subsidence in China in detail, and to provide basic information for groundwater management, urban planning and infrastructure construction layout in China.
The InSAR monitoring results of land subsidence in North China Plain and Yangtze River Delta effectively guide the layout and construction of ground monitoring networks in various regions. Through the cooperation with geological environment stations in Beijing, Tianjin, Shanghai and other provinces and cities, the key subsidence areas concerned by various regions are investigated and monitored in detail, which directly serves the local needs. In addition, it also provided technical data and achievements for the Third Design Institute of the Ministry of Railways, Tangshan Branch of the General Research Institute of Coal Science, Shandong Lubei Engineering Survey Institute, Hebei Hydrogeology Engineering Geology Team 4 and other units and organizations.
On June 20 10, China Geological Survey issued the bulletin "The Application Effect of InSAR Technology in Land Subsidence Investigation and Monitoring in China is remarkable" in the form of a special report on geological survey, and introduced the achievements and advanced experience of InSAR technology research and development. 20 1 1 At the beginning of this year, the largest InSAR monitoring technology training and surface deformation seminar in China was held in Beijing, sponsored by China Geological Survey and hosted by Aerospace Center. More than 120 people from quality and environmental monitoring departments, universities, scientific research institutes and other institutions all over the country participated in this training, and invited experts from Italy, Germany, Canada and other countries and institutions to give special lectures.
The main ways of promotion and transformation are conference exchange, technical training and technical consultation.
Technical support unit: China Land and Resources Aerogeophysical Remote Sensing Center.
Contact: Ge Xiaoli
Address: Institute of Remote Sensing Technology, Hangyao Center, No.31Xueyuan Road, Haidian District, Beijing.
Postal code: 100083
Tel: 0 10-6206005 1
E-mail :gxiaoli@sohu.com