Monitoring and analysis of mining 3D time-series deformation based on multi-track SAR data

Accurate monitoring of the developing process of a surface subsidence basin is the basis of building damage assessment and surface deformation prediction. In this paper, the Synthetic Aperture Radar (SAR) data of three different imaging geometries, TerraSAR, Radarsat-2, and Sentinel-1A, were exploited. Firstly, two-dimensional (2D) time-series deformation of the surface subsidence basin caused by 15,235 working face mining was obtained based on Multidimensional Small Baseline Subset (MSBAS) technology from 19 December 2015 to 5 March 2016. By comparing vertical deformation with levelling data, it is shown that the root-mean-square error of vertical deformation is 3.2 mm and the standard deviation is 1.9 mm when the ascending-descending track SAR data is available. Otherwise, the root-mean-square error of vertical deformation is 18.1 mm and the standard deviation is 11.6 mm. Because of the low precision of the north–south horizontal movement monitored by the SAR sensor, the vertical deformation acquired by MSBAS technology and the rules of the mining subsidence (horizontal movement is proportional to tilt) were combined to obtain the north–south horizontal movement which was proven to be reliable by comparing the 2D time-series deformation obtained by MSBAS technology. Then, the deformation of the railway in the surface subsidence basin was analysed based on the three-dimensional (3D) time-series deformation. The results show that the subsidence, tilt, and horizontal movement strongly influence the railway in the monitoring period, but will not affect the normal traffic. This experiment lays a technical foundation for preventing the occurrence of mining disasters and verifies the ability to monitor the deformation of buildings and structures by interferometry synthetic aperture radar technology.     

A method of monitoring three-dimensional ground displacement in mining areas by integrating multiple InSAR methods

Underground mining often causes large-gradient vertical and horizontal displacement in ground surface, resulting in the losses of coherence and difficulties in phase unwrapping. This article presents an approach to determine three-dimensional ground displacements in mining areas with the large gradient or phase decorrelation by integrating multiple interferometric synthetic aperture radar (InSAR) methods. The core of the proposed method is that the offset-tracking method is employed to solve for the displacement with the large gradient or phase decorrelation. First, the displacements in the radar line-of-sight directions are obtained from two interferometric pairs with different viewing geometries by integrating the measurements of differential InSAR and offset tracking. Then, the displacements in the azimuthal directions are obtained from two interferometric pairs with different viewing geometries by integrating the measurements of multiple aperture interferometry and offset tracking. Finally, the three-dimensional ground displacement fields are inferred from these four independent, one-dimensional displacements using the least squares method and Helmert variance component estimation. We apply this method to obtain the three-dimensional ground displacement field in the Dongtan mine region. We compare the results with those of levelling and global positioning system surveys, and the root mean square errors of the results were 24 and 43 mm in the vertical direction and horizontal directions, respectively. The experimental results indicate that the proposed method can be used to estimate three-dimensional ground displacement fields in mining areas with large-gradient displacement and phase decorrelation.     

The present status of subsiding land vulnerable to roof collapse in the Jharia Coalfield,India, as obtained from shorter temporal baseline C-band DInSAR by smaller spatial subset unwrapped phase profiling

In this paper, we identified recently subsiding areas in Jharia Coalfield, Jharkhand, India from the shorter temporal baseline Radarsat-2 C-band interferometric synthetic aperture radar (InSAR) data pairs of 2012. Although shorter wavelength C-band differential InSAR (DInSAR) is more sensitive to slow deformation and better suited for higher precision land subsidence measurement, the dynamic and adverse land cover in mining areas and resulting temporal decorrelation problem poses a serious problem for DInSAR observation in mining areas. We used smaller temporal baseline data pairs and adopted InSAR coherence-guided incremental filtering with smaller moving windows to highlight the deformation fringes over temporal decorrelation noise. We identified the deformation fringes and validated them based on ground information to prepare the land subsidence map of the coalfield in 2012. Several new, previously unreported subsidence areas were detected in the present study with a total subsiding area of 6.9 km². The recent incidence of roof collapse on 15 November 2014 at Angar Patra village in Katras region of the coalfield where 45 houses collapsed and 10 people were injured is situated in a highly subsiding vulnerable area as obtained from the present study. Due to spatial discontinuities of InSAR coherence, DInSAR phase unwrapping for the entire study area in one go did not appear feasible. To avoid this problem, we performed DInSAR processing in smaller spatial subsets and unwrapping of the subset interferograms by a ‘minimum cost flow’ algorithm. Subsequently, we plotted unwrapped phase profiles across the deformation fringes and retrieved the maximum deformation phase with respect to background phase and translated them into radar line of sight (LOS) displacement rates. For obtaining the average subsidence rates, we adopted InSAR coherence-weighted LOS displacement rates taking into account the contribution of each data pair as a function of DInSAR phase quality of the fringe areas. Ground-based subsidence measurements by precision levelling were conducted in four test sites that had been undergoing active underground mining during the observation period. We compared space-borne DInSAR-based subsidence rates obtained by the adopted technique with precision levelling measurements. Overall, the results are found to agree well. In the four test sites with gentle to flat topography, land subsidence occurs at slow to moderate rates due to compression of in-filled material (resulting from sand stowing in underground mining), without any evidence of roof collapse. In such cases, the horizontal displacement component is less significant, and overall surface displacement occurs essentially in the vertical direction. However, we assessed the nature of subtle horizontal strain to infer relative shrinkage or dilation of the land surface which could be additive or subtractive to vertical displacement in DInSAR-based LOS displacement.     

Monitoring of large-scale deformation in mining areas using sub-band InSAR and the probability integral fusion method

The large-scale and rapid land subsidence that occurs in mining areas often leads to problems, such as densely spaced interference fringes and the temporal decorrelation of interferometric synthetic aperture radar (InSAR) interferograms. To solve these problems, sub-band InSAR is applied to monitor the large-scale deformation that occurs in mining areas. First of all, four different bandwidth images with three sub-band bandwidth parameters are used to extract simulated mining-induced subsidence with seven different deformation magnitudes. The results of the simulation experiment suggest the following conclusions. In monitoring subsidence with different deformation magnitudes using images with different bandwidths, an optimal monitoring value exists; wider image bandwidths lead to smaller optimal monitoring values and higher monitoring accuracies. Therefore, an appropriate sub-band bandwidth should be selected that depends upon the image bandwidth and the subsidence level to achieve optimal monitoring. The optimal sub-band bandwidth for monitoring subsidence of different magnitudes in mining areas is determined through simulation experiments, and these conclusions can provide a technical basis for selecting the appropriate sub-band bandwidth for the monitoring of subsidence in mining areas. Although sub-band InSAR can reduce the number of interference fringes and the difficulty of unwrapping, the simultaneous introduction of large amounts of noise leads to reduced monitoring precision, and the application of the probability integral method in the prediction of mine subsidence is more mature. Therefore, the combined use of sub-band InSAR and the probability integral fusion method to monitor mining-induced deformation is proposed in this paper. The probability integral method is used to perform noise peeling on the interferometric phases of the sub-bands to improve the monitoring accuracy of sub-band interferometry. Then, according to the results of the simulation experiment, the fusion method with the appropriate sub-band bandwidth parameters is applied to monitor the surface deformation associated with working face 52,304 from 2 December 2012 to 13 December 2012. Finally, the monitoring results are compared with the results of monitoring using conventional differential interferometric synthetic aperture radar (D-InSAR) and global positioning system (GPS) field survey data. The results show that the reliability and accuracy of the fusion method are much better than those of conventional D-InSAR in monitoring the large-scale deformation that occurs at the edges of subsidence basins.     

Obtaining Coseismic Deformation Field of Jiuzhai Earthquake with Sentinel-1A

Based on C-band SAR data of Sentinel-1A satellite，two-pass Differential Interferometric Synthetic Aperture radar (D-InSAR) method was applied for analyzing the ground displacement due to the August 8，2017 Jiuzhaigou MS 7.0 earthquake shock.It obtained the study area coseismic deformation field.The interference results show that the earthquake caused obvious surface deformation，and the maximum uplift in the scenic area reached 12.6 cm，and the maximum settlement was 9.8 cm.The results show that the C-band radar data of Sentinel-1A satellite is very suitable for the detection of D-InSAR deformation in areas with dense vegetation and complex terrain.The ground deformation information obtained by D-InSAR technology can be used to analyze and discuss the scope of earthquake disaster and the mechanism of earthquake.The important status of D-InSAR technology in the field of large scale surface deformation detection and geoscience research are further clarified.     

Episodic ground deformation signals in Thessaly Plain (Greece) revealed by data mining of SAR interferometry time series

The Eastern Thessaly Plain presents an area of severe settlement phenomena, owing to the over-exploitation of the underground aquifer systems, causing significant damages to national infrastructures and private properties annually. Herein, both Persistent Scatterers (PS) and Small Baselines (SB) interferometric techniques were applied to study the history of ground deformation along the entire plain. Although the area consisted mostly of agricultural land, a sufficient number of point targets was obtained, well-distributed over the entire plain, permitting the recognition of spatial variations of the displacement field in addition to temporal trends. Our findings outline the southern part of the basin as the mostly affected area, whereas local subsidence patterns of lower magnitude were also recognized elsewhere. Episodes of significant ground subsidence, reaching several centimetres within a few months, characterize the deformation pattern of the area. Although average ground deformation rates do not exceed 2 cm year^?1, line-of-sight (LOS) displacements of up to 13 cm were observed, occurring during the summer–autumn periods. A geographic information system (GIS)-based post-processing approach for the analysis of synthetic aperture radar (SAR) time series is presented, by which these abrupt settlement episodes can be identified in both temporal and spatial domains. The analysis allows the separation between rapid subsidence phenomena during the summer–fall season and annual deformation rates, thereby providing valuable information regarding the actual deformation pattern of the area. The results confirm in situ geological observations, highlighting the unique behaviour of the area due to intense water pumping. The study underlines that average SAR displacement rate maps might be inadequate to describe complex deformation scenarios and could lead to misinterpretations. Exploitation of the full capacity of SAR time series by detailed examination of the displacement histories, through a tailored data-mining strategy, could provide valuable information to geotechnical engineers and planners.     

Analysis of deformation over permafrost regions of Qinghai-Tibet plateau based on permanent scatterers

The surface displacement by seasonally freezing bulge and thawing subsidence are the main hazards for engineering construction in permafrost regions, especially for the Qinghai-Tibet railway. One of the main problems is how to monitor the frozen ground's displacement in the process of construction and protection of the Qinghai-Tibetan railway. The technology of Permanent Scatterers (PS) has been successfully used to detect the long-term subsidence at urban areas. For detecting the subsidence of the frozen earth on Qinghai-Tibet Plateau, this paper extended the capability of the technology of PS to investigate deformation phenomena in vegetated area. The paper analyses an interferometric phase model, and presents improved PS algorithms for separating different components in interferometric phase. The proposed technique is implemented using ENVISAT ASAR images to detect the deformation over permafrost region of Qinghai-Tibet Plateau. The results are in concordance with results provided by a traditional ground levelling, which encourages future development using the Permanent Scatterers method to analyse deformation of the frozen earth on Qinghai-Tibet Plateau.     

Recent subsidence in Tianjin,China: observations from multi-looking TerraSAR-X InSAR from 2009 to 2013

Tianjin, China, has been suggested to have serious ground subsidence due to excessive extraction of groundwater. It is essential to monitor this subsidence, which has potential hazards and risks. Time series InSAR (TS-InSAR), such as small baselines subset (SBAS), is a powerful tool that can monitor ground deformation with high accuracy and at high spatial resolution over a long time interval. However, the high computational complexity may exceed computer memory limit when high-spatial resolution SAR (such as TerraSAR-X, TSX) images are used. In this article, the multi-look approach is introduced to the SBAS tool from StaMPS/MTI (Stanford method for persistent scatter/multi-temporal InSAR) in order to balance the spatial resolution and subsidence information in detection. The looks used for multi-looking are first fixed in terms of the accuracy of deformation and the density of coherent points. Then, the recent subsidence in Tianjin is extracted using multi-looking SBAS based on 48 TSX images acquired from 2009 to 2013. The results are validated by levelling measurements with a root mean square error (RMSE) of 4.7 mm year^–1, which demonstrates that SBAS analysis can effectively monitor deformation based on multi-looking TSX acquisitions in the area under investigation. Besides, the results also show that Tianjin has been suffering from subsidence during this period, and there were two separate large subsidence basins located in this study area with more than 500 mm cumulative subsidence. Moreover, the subsidence rate increased after December 2010 in Tianjin.     

基于D-InSAR技术的淮南矿区地面沉陷监测

针对常规的通过大地水准测量、GPS测量监测矿区地面沉陷的技术存在监测周期长、成本高、无法全面监测等缺陷,提出了一种基于D-InSAR技术的矿区地面沉陷监测方法。以淮南矿区为试验区,采用两轨法D-InSAR技术,利用该地区2个时相的ALOS PALSAR数据获取了淮南矿区试验时间段内的地面形变图,分析了淮南矿区各矿的地面沉陷信息。结果表明,煤矿开采区存在5~25 cm不同程度的沉陷,与实际情况相符,因此,基于D-InSAR技术的监测方法可以作为一种获取矿区大范围的地表沉陷信息的有效方法。     

Subsidence analysis of ELH Bridge through ground-based interferometric radar during the crossing of a subway shield tunnel underneath the bridge

Ground-based interferometric radar is a popular technique for the deformation monitoring and analysis of civil engineering constructions. Many researchers have applied this technique to different operative scenarios, but only a few studies have analysed deformation time series derived through ground-based interferometric radar in consideration of the effect of coloured noise. In this study, deformation information was retrieved through the joint application of ground-based interferometric radar and maximum likelihood estimation (MLE) in consideration of the effects of white and coloured noises. A case study was conducted on the subsidence of East Lake High-tech Bridge during subway shield tunnel crossing underneath this bridge (from 16 to 18 November 2016). The subsidence time series was derived through ground-based interferometric radar. Afterward, the subsidence time series was verified by levelling at an accuracy better than 0.33 mm. Furthermore, white and coloured noises were detected in the denoized subsidence time series through a spectral analysis and MLE. For the subsidence time series of Nos. 7 and 8 piers, the coloured noise amplitudes were 0.3824 and 0.6261 mm, respectively, and the white noise values were 0.0414 and 0.0610 mm, respectively. Accurate subsidence rates and accumulative subsidence were derived through MLE by using the estimated noise characteristics in the subsidence time series. The subsidence rates of Nos. 7 and 8 piers were ?0.0122 ± 0.0060 and ?0.0065 ± 0.0058 mm hour^?1, respectively, and the accumulative subsidence values were ?0.6365 and ?0.3370 mm, respectively. This finding suggests that the bridge is stable and safe.     

Integrated space geodesy for mapping land deformation over Choushui River Fluvial Plain,Taiwan

Groundwater is an important part of the precious water resources. As the fresh surface water resources become scarcer because of climate change, population growth, and industrial activities, more and more groundwater has been extracted to meet the demands of various water uses (e.g. municipal, industrial, and agricultural). Excessive groundwater extraction leads to severe ground subsidence which compromises the safety of surface and underground infrastructures. Modelling the effects of groundwater extraction is vital to the management and sustainable use of groundwater. However, results of such modelling have to be validated with inputs such as the field survey of ground subsidence. Levelling and continuous global positioning system (GPS) receiver networks are routinely used to collect these field measurements. Unfortunately, these techniques have limitations in terms of areal coverage and density of survey marks and, as a result, subsidence hot spots can be easily missed out. In order to provide a comprehensive picture of subsidence to aid geotechnical modelling and to assess the effectiveness of measures used to mitigate ground subsidence, satellite imaging radar interferometry techniques (interferometric synthetic aperture radar (InSAR) can be used to complement other deformation monitoring techniques. In this study, 20 Advanced Land Observing Satellite (ALOS) Phased Array L-band Synthetic Aperture Radar (PALSAR) images acquired from 31 December 2006 to 26 February 2011 were used to map the land displacement over the Choushui River Fluvial Plain (CRFP), Taiwan. The GPS measurements acquired at 10 continuously operating reference stations (CORS) were used to refine the orbit error in the each differential interferogram obtained from each radar image pair. The displacement time series over the distributed scatterers and the persistent scatterers were analysed. Several subsidence bowls were identified in CRFP. A quantitative comparison was conducted to compare the radar measurements to the GPS measurements over 36 GPS CORS stations. Good agreement between both measurements was observed with coefficient of determination (R²) of 0.97, absolute mean difference of 3.2 mm year^?1, and standard deviation of 4 mm year^?1. The InSAR-measured Line-of-Sight displacement and GPS-measured horizontal displacement were integrated to derive the vertical displacement map. Two displacement maps were generated using two ALOS-2 PALSAR-2 pairs acquired between 2015 and 2016. Similar subsidence patterns were found in the two maps compared to the 2006–2011 displacement rate map, suggesting the land over the same region might have continued to fall.     

Surface movements in Bologna (Po Plain — Italy) detected by multitemporal DInSAR

We studied the surface deformations affecting the southeastern sector of the Po Plain sedimentary basin, in particular the area of Bologna. To this aim an advanced DInSAR technique, referred to as DInSAR-SBAS (Small BAseline Subset), has been applied. This technique allows monitoring the temporal evolution of a deformation phenomenon, via the generation of mean deformation velocity maps and displacement time series from a data set of acquired SAR images. In particular, we have processed a set of SAR data acquired by the European Remote Sensing Satellite (ERS) sensors and compared the achieved results with optical levelling measurements, assumed as reference. The surface displacements detected by DInSAR SBAS from 1992 to 2000 are between 10 mm/year in the historical part of Bologna town, and up to 59 mm/year in the NE industrial and agricultural areas. Former measurements from optical levelling referred to 1897 show 2-3 mm/year vertical movements. This trend of displacement increased in the second half of the 20th century and the subsidence rate reached 60 mm/year. We compared the more recent levelling campaigns (in 1992 and late 1999) and DInSAR results from 1992 to 1999. The standard deviation of the difference between levelling data, projected onto the satellite Line Of Sight, and DInSAR results is 2 mm/year. This highlights a good agreement between the measurements provided by two different techniques. The explanation of soil movements based on interferometric results, ground data and geological observations, allowed confirming the anthropogenic cause (surface effect due to the overexploitation of the aquifers) and highlights a natural, tectonic, subsidence.     

Surface deformation over the buried Nasr Abad salt diapir,Central Iran using interferometric synthetic aperture radar data

ABSTRACT

This study employs interferometric synthetic aperture radar (InSAR) data sets to monitor the surface deformation of the Nasr Abad buried salt diapir in the Central Basin of Iran. The Nasr Abad salt diapir is one of the largest buried salt diapirs in Iran and could be ideal site for oil/gas storage and industrial waste disposal. In this study, we use 40 advanced synthetic aperture radar (ASAR) images from Environmental Satellite (EnviSat) to analyse surface displacement rates of Nasr Abad diapir and its surrounding regions. A time series of line-of-sight (LOS) displacements on the residual cap above the buried diapir were obtained from both descending and ascending images between 2003 and 2010 by applying the Small-BAseline Subset (SBAS) technique. Tropospheric artefacts in the displacement interferograms were mitigated using the power-law correction method in Toolbox for Reducing Atmospheric InSAR Noise (TRAIN) software. Finally, the data for temperature, precipitation, and tidal forces were correlated with the time-series displacement results of four points that located on the residual cap. Our results indicate that surface above the diapir and an area of about 2 km² subsided with maximum LOS velocity of about 7 mm year^?1 for ascending images and 5 mm year^?1 for descending images. The amount of vertical subsidence derived from LOS decomposition in reactive stage of Nasr Abad salt body is about 7 mm year^?1. Comparing the temperature and precipitation data with the time series of displacement confirmed that the salt expands when temperatures increases and that salt flow accelerates when it is wet. The displacement pattern retrieved from InSAR analysis is in good agreement with intervals near maximum and minimum solid earth tides. Monitoring the activities of the Nasr Abad region over 7 years shows that the region of surface subsidence is confined to the area along the Khurabad and AbShirin-Shurab Fault zones in the southern Central Basin.     

Deformation monitoring over large areas with multipass differential SAR interferometry: a new approach based on the use of spatial differences

Multipass differential synthetic aperture radar interferometry is becoming increasingly important as a powerful technique for ground deformation retrieval compared with classical geodetic techniques such as levelling and global positioning system (GPS). It proves superior in terms of costs, coverage, data accessibility and availability of historical archives. Application to different areas of risk management such as monitoring of volcanoes and slope instabilities, tectonic movements, urban areas and infrastructure, has already been successfully demonstrated. In this work we discuss a new multipass differential synthetic aperture radar interferometry processing technique that makes extensive use of spatial differences. The results obtained demonstrate that this technique allows the monitoring of ground deformation over wide areas. The processed data were acquired from ERS–1 and ERS–2 sensors over three partially overlapping tracks related to a region, approximately 240 km N–S and 80 km E–W wide, located in the centre‐south of Italy, along the west coast. Comparison of the mean deformation velocity results over the different tracks and of the deformation evolution with levelling measures, available in some areas, shows good agreement and goes to validate the technique.     

An approach for accurately retrieving the vertical deformation component from two-track InSAR measurements

As is well known, both conventional differential synthetic aperture radar interferometry (D-InSAR) and multi-temporal synthetic aperture radar interferometry (MT-InSAR) have a common limitation that they only can measure the deformation component along the radar line of sight (LOS) direction. However, in the majority of disaster investigations, there is more interest in the vertical deformation component than that of the horizontal direction, for example, in measuring ground subsidence in urban areas, or ground subsidence due to underground mining. To estimate the vertical deformation component accurately, it is in theory necessary to create at least three independent equations, and solve the vertical, the North–South, and the East–West deformation components by exploiting at least three-track InSAR LOS measurements or combining at least two-track InSAR LOS measurements with azimuth measurements. However, these methods are greatly limited and sometimes not even practical because there is typically little chance of obtaining a three-track SAR data set covering the same area in the same time span, and the accuracy of the azimuth measurements is far lower than that of InSAR LOS measurements. In this article, we found that it is possible to solve for the vertical deformation component from two-track InSAR LOS measurements in some circumstances. Then, an approach for accurately retrieving the vertical deformation component from two-track InSAR LOS measurements is proposed, and the analytical expression is presented. The approach is illustrated through an investigation of the ground subsidence in an area of Beijing, China. Unlike previous methods, this approach can accurately retrieve the vertical deformation component from two-track InSAR LOS measurements, and provide more reliable results for improving the interpretation of ground subsidence phenomena.     

多模式雷达在矿区沉降监测中的应用研究

合成孔径雷达差分干涉测量(DInSAR)技术在地表形变监测方面已得到广泛应用。介绍了将差分InSAR技术运用于矿区地表沉降监测,获得了河北峰峰煤矿地表Envisat/ASAR和ALOS/PALSAR的雷达形变干涉相位图,并对Envisat C波段和ALOS L波段的形变干涉相位图进行了相干特性和相位特性的分析。通过综合考虑C波段和L波段的优势与不足,将两者联合使用,实验表明利用多模式雷达数据对矿区地表沉降进行检测的可行性。同时,通过对雷达干涉相位图的分析,能够及时提供正在进行地下开采活动的矿区地理位置。     

Analysis of ground subsidence at a coal-mining area in Huainan using time-series InSAR

In Huainan City, Anhui Province, China, ground subsidence persistently occurs due to underground coal mining, which has caused several environmental issues. A modified time-series Interfermetric synthetic aperture radar (InSAR) technique is applied to obtain ground movement in Huainan over a period of approximately two years using 20 ascending Radarsat-2 images. In particular, distributed scatterers (DSs) are efficiently identified using classification information and statistical characteristics. Classified information is used to identify the specific DS classes and statistical characteristics are used to refine the DS candidates. To control error propagation and improve computational efficiency, the deformation rate and digital elevation model (DEM) error of persistent scatterers (PSs) are first retrieved using conventional persistent scatterer intermemetry (PSI). Then, a region-growing-based strategy is applied to extract the deformation rate of DSs. Land subsidence is detected in coal-mining areas of central Dingji, Guqiao, Zhangjiaji, Xinji I, and Xinji II, which suggests that the subsidence is primarily caused by underground mining. The fastest subsidence occurring in non-urban areas is particularly vulnerable to subsidence and collapsed lakes. It is also found that the collapsed lakes have expanded during the observation period, with an expanded mining area of 0.842 km² near Guqiao. A linear relationship between the observed subsidence and expansion of collapsed lakes was found, which indicates that the expansion of collapsed lakes hass resulted from subsidence due to underground coal mining.     

Deformation mapping in three dimensions for underground mining using InSAR – Southern highland coalfield in New South Wales,Australia

This article presents 3D surface deformation mapping results derived from satellite synthetic aperture radar (SAR) data acquired over underground coal mines. Both ENVISAT Advanced Synthetic Aperture Radar (ASAR) and Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) data were used in this study. The quality of the 3D deformation mapping results due to underground mining is mainly limited by two factors. (1) Differential interferometric synthetic aperture radar (DInSAR) is less sensitive to displacement along the north–south direction in the case of the current SAR satellite configurations. (2) The mining-induced displacement is continuous and nonlinear; and the accuracy of the 3D DInSAR measurement is severely affected by the similar but non-identical temporal overlaps of the InSAR pairs. The simulation and real data analyzes have shown that it would be more practical to use DInSAR pairs with the assumption of negligible northing displacement to derive the displacements in the easting and vertical directions. The northing displacement could then be estimated from the residuals. This limitation could be overcome in the future with the launch of more radar satellites, which would provide better viewing geometry.     

2种灰色模型在矿区地表沉陷预计中的适用性

目前矿区地表单点沉陷动态预计方法主要基于传统的水准测量数据,监测方法单一,成本高,观测点易破坏,不能保证地表形变信息的实时性,且采用灰色模型进行地表沉陷预计时只针对单一模型的应用,没有结合模型自身特点分析其适用性。以袁店二矿7221工作面为试验区域,采用合成孔径雷达差分干涉测量技术监测矿区地表沉陷量,分别建立了描述沉陷量与时间关系的GM(1,1)与灰色Verhulst模型进行地表沉陷量预计,实现了矿区地表沉陷监测与动态预计一体化。通过比较、分析GM(1,1)与灰色Verhulst模型对地表沉陷量的拟合及预计结果,得出了2种灰色模型在矿区地表沉陷预计中的适用性:在矿区开采沉陷开始至活跃前期,若地表单点沉陷量曲线呈近似单峰型,则宜采用GM(1,1)进行短期预计;当矿区地表沉陷进入衰退阶段,单点沉陷量曲线呈平底饱和状态,则宜采用灰色Verhulst模型进行中长期预计。     

基于SBAS-InSAR技术的煤矿开采沉陷监测与分析

地下煤炭资源大量开采导致的地表形变,引发严重的安全和环境隐患,雷达干涉测量技术是高精度、大范围地表形变监测的重要手段之一。以辽宁省沈阳市沈北新区蒲河煤矿为例,采用SBAS-InSAR技术探测2018—2019年矿区地表形变结果,获取了采煤引起地表形变的时空分布特征,结合采场所在区域的地质条件和变形诱发因素,利用数值模拟技术对观测形变结果进行模拟分析,进而讨论了蒲河煤矿地面沉降在时间和空间上的变形规律和机制。InSAR形变监测结果显示,开采区域内存在两处沉降漏斗,且数值模拟结果与InSAR形变观测值分布规律一致,反演结果接近实际情况,可为相关部门制定地面沉降防治措施提供科学依据。