Real Time Subsidence Monitoring Techniques in Undercity Mining and a Case Study: Zonguldak Undercity Applications-Turkey

Transcription

1 Real Time Subsidence Monitoring Techniques in Undercity Mining and a Case Study: Zonguldak Undercity Hakan AKCIN, Hakan S. KUTOGLU, Turkey Keywords: Undercity mining, subsidence, PALSAR, RADARSAT, GNSS. SUMMARY Earthquake, flood, avalanche and landslide are well-known disasters. Along with the growing settlements, irregular urbanization, development of uncontrolled settlement cause risk to grow and the size of today s disasters clearly displays these problems. In cities where mining is employed subsidence is an important mechanism causing problems similar to such disasters. In addition, it has been declared by the law that subsidence is a natural disaster affecting daily life. With the purpose; an experimental study based on GNSS and InSAR analyses was realized by monitoring the temporal progress of surface changes and their subsidence effects on buildings in Zonguldak Metropolitan Area-ZMA of Turkey. There are five municipalities and people living in the region now. Hardcoal production is about 3 million tons/year in ZMA where the core of mining activity belongs to Turkish Hardcoal Enterprises (THE), private sector and illegal manufacturers. In this study, subsidence areas and amounts were analyzed by using periodically taken RADARSAT and PALSAR radar images. C-band and L-band SAR interferometry with the images for building areas were used in monitoring of mining induced land subsidence. By the subsidence disaster; effect of many buildings and roads in settlement within the urban area arising from underground productions in coalfields of ZMA were determined. Areas where building intensity is high were extracted and amount of deformation was found to be 204 mm during 132 days from the real time monitors by GNSS and InSAR techniques. Finally, local ground deformations and environmental changes in forestry and settlement area around ZMA coalmines were also detected using L-Band PALSAR data. TS 5D - Landslide and Subsidence Monitoring I Commission: 6 1/12

2 Real Time Subsidence Monitoring Techniques In Undercity Mining and a Case Study: Zonguldak Undercity Hakan AKCIN, Ş. Hakan KUTOGLU, Turkey 1. INTRODUCTION InSAR and GNSS are effective tools to measure the amount of ground deformation caused by subsidence in populated areas (Deguchi 2006, Ge 2001, Nga 2008, Raucoules 2003). PALSAR and RADARSAT are two important radar missions in the monitoring of deformations by Interferometric SAR. This achievement is due to the fact that PALSAR uses L-band microwave which is less affected by vegetation and atmosphere. Furthermore, PALSAR, launched in January 2006 as a successor of JERS-1/SAR, is expected to make contributions in the fields of disaster and environmental monitoring. Though susceptible to the effect of vegetation, C-band microwave is capable of detecting deformations less than a centimeter due to its high sensitivity. The applications of InSAR technique using C-band microwave have been reported in the measurement of ground subsidence in the urban area and the detection of ice sheet flow (Deguchi 2005, Rodriguez 1992, Raucoules 2007). In this study, we determined ground deformation and temporal changes induced by coal mining development in terms of environment using InSAR technique with C- and L-band SAR data, then tried to verify the accuracy using GNSS measurement data. All this techniques are used for real-time monitoring of subsidence zones in populated areas of ZMA. Figure 1. Study area (mosaic image Republic of Turkey produced by JERS-1/SAR) and hardcoal production fields in ZMA (Radar-left and ASTER-right image, NEDO 1991). There are three hardcoal mining sub-companies of Turkish Hardcoal Enterprises in ZMA, namely; Kozlu, Uzulmez and Karadon (Figure 1). In Kozlu Hardcoal Company, especially, all the mining activities has realized under urbanized areas including structures such as highways, TS 5D - Landslide and Subsidence Monitoring I Commission: 6 2/12

3 university campus, high schools, and apartments. Six longwall panels have been being mined at a depth of approximately between -200m and -600m in Kozlu. 3-D view of these panels is shown in Figure 2. The activity of underground coal mining in Uzulmez and Karadon has been conducted by Turkish Hardcoal Enterprises and several private companies. Moreover, many unauthorized illegal coal mining activities are seen in the surrounding area and they are produced subsidence in populated area as well. In this study, subsidence effects of these activities were also discussed. Figure 2. 3-D view of longwall coalmine panels, underground tunnels and shafts in Kozlu region (URL1). 2. SUBSIDENCE MONITORING TECHNIQUES USED FOR UNDERCITY APPLICATIONS OF ZMA 2.1. Verification of RADARSAT data In analysis of RADARSAT data, temporal change of ground deformation was measured by using 15 pairs whose baselines were less than 500 m between 2006 and In order to measure time series of deformation, we applied the smoothness-constrained least squares method to the pixels satisfying (a) and (b) below: a) Capable of phase unwrapping b) Coherence values greater than 0.1 TS 5D - Landslide and Subsidence Monitoring I Commission: 6 3/12

4 RADARSAT is C-band microwave sensor and it is difficult to provide high coherence between master and slave image in densely vegetated areas. Consequently, fringe with spatial continuity was observed only in the urban district in this study area. Deformation of over 55 mm per 15 months in slant range direction was detected in the urban area located near Kozlu mining region. The location of deformation extracted by RADARSAT is at the extension of existing mining tunnel and it corresponds to the currently ongoing mining activity (Figure 3). Figure 3. Deformation map from RADARSAT and mining activities under sea port, university campus, high schools and highway in Kozlu region Verification of ALOS- PALSAR data In order to measure deformation in the vegetated area, L-band microwave having longer wavelength than C-band are necessary. Basically, periodic observation by PALSAR is TS 5D - Landslide and Subsidence Monitoring I Commission: 6 4/12

5 effective. In the result of analysis using PALSAR data, local deformation was detected in 3 areas. These deformations were approximately 3 to 4 cm per 46 days and were extracted in Uzulmez and Karadon regions (Figure 4). They are detectable by PALSAR, but not by RADARSAT. The authors will present the latest analysis results using the updated PALSAR data /8/ /3/ /9/27 Figure 4. Temporal changes of the amount of land deformations using PALSAR image series on ZMA Verification of GNSS Data In order to verify InSAR results 15 deformation monitoring points for GNNS measurements were installed within the urbanized area in Kozlu region. In these points, periodical control observations synchronized with production in longwall panels were realized. For observed dates post processing by statistical adjustment was done. Furthermore, displacement in these points was analyzed by θ 2 method Location of subsidence zones inside of urbanized areas on ZMA For this purpose, two types of application were utilized. First one includes the Landsat images (only bands 1,4 and 7) dated as 2000 with the ground resolution of 15m. These spectral channels were analyzed by PCI Geomatica V9.1.1 software package. Second one is Landsat image analysis based on the object oriented approach using ecognition 3.0 software. At this stage; scale, color, shape, smoothness and compactness parameters were assigned as 30, 0.8, 0.2, 0.9 and 0.1, respectively. After automatic segmentation, in differentiation of pure settlement areas and forestry areas, unsolved segments were manually corrected and thus, vectorized classes were derived. Also, this classified and vectorized Landsat image and InSAR deformation map were superimposed with GIS applications. In this way, locations of mining induced subsidence zones in populated areas of ZMA were determined. In Figure 5, superimposed shape of RADARSAT, JERS-1 SAR for constitutions before 2000 and PALSAR images are shown. This subsidence area was extracted in the PALSAR and RADARSAT images covered by an intense settlement area. TS 5D - Landslide and Subsidence Monitoring I Commission: 6 5/12

6 Figure 5. Interferometric SAR images superimposed onto the vectorized classes on ZMA. 3. RESULTS PALSAR and RADARSAT images with similar temporal coverage were searched for urbanized area in ZMA. In the results of RADARSAT data obtained from two local surface displacements were detected in the vicinity of Kozlu mine. The amount of deformation was approximately 4.4 cm/year in slant range direction. Municipal plan controlling development and constructions within Kozlu region of ZMA related to the subsidence areas extracted by InSAR from RADARSAT are shown in Figure 6. Building damage and ground deformations monitored in surface is also shown in Figure 7. Totally, cm vertical displacements and 12-25cm horizontal displacements were determined for the maximum founded points of θ 2 criteria from processing of the GNSS measurements between 2005 and 2009 in deformation observed points. Determined horizontal and vertical displacement vectors are shown in Figure 8. TS 5D - Landslide and Subsidence Monitoring I Commission: 6 6/12

7 Figure 6. Deformation map from RADARSAT image and Municipal plan controlling development and constructions within Kozlu region. TS 5D - Landslide and Subsidence Monitoring I Commission: 6 7/12

8 Figure 7. Damages on the High school Buildings Figure 8. Horizontal and vertical displacements from periodical GNSS measurements on the highway within the Kozlu region between 2005 and Figure 9. Subsidence zones within the populated area determined from the PALSAR image between 2007 and 08. TS 5D - Landslide and Subsidence Monitoring I Commission: 6 8/12

9 Temporal changes in populated areas using by PALSAR results in was confirmed. In these regions, irregular mining activities operated by several private companies were determined. Also, four important subsidence zones determined from the investigation of temporal changes is shown in Figure 9. Zones 1, 2 and 3 are within the Uzulmez region of the ZMA. However, zone 4 is within Karadon region. In Figure 10 and 11, the influence area and locations of zones 1, 2 and 3 are given on optical image and municipal plan and the subsidence influence area and location of zone 4 is shown in Figure CONCLUSIONS AND FURTHER WORKS By using JERS-1/SAR, RADARSAT and PALSAR data, mining induced land deformation was detected in the urbanized area of Metropolitan Area-ZMA. Following findings were obtained from the study: In the results of RADARSAT data obtained between 2005 and 2008, two local surface displacements were detected in the populated zones of Kozlu region. The amount of deformation was approximately 4.4 cm/year in slant range direction surrounds education buildings, apartments and a highway in planned areas by Municipality of Zonguldak. For the accuracy of measurement, InSAR results were compared to the GNSS measurement data within 2 cm variance. Local ground deformations were also detected around Karadon and Uzulmez mines using PALSAR data for vegetated areas within the ZMA. These deformations were extracted near the existing private coal mine and the area of development activities and these results clearly indicate that all deformations were induced by mining activity. Subsidence Effect Area 2 Subsidence center 1 Subsidence center Privite coal mines Privite coal mines Subsidence center 3 Privite coal mines Figure 10. Privite hardcoal mines and subsidence influence areas used PALSAR in Uzulmez. TS 5D - Landslide and Subsidence Monitoring I Commission: 6 9/12

10 Figure 11. Determined subsidence effect areas used PALSAR on municipal plan. Figure 12. Subsidence effect to planed area by municipal of Karadon Region. TS 5D - Landslide and Subsidence Monitoring I Commission: 6 10/12

11 In the case of resource development by underground mining, the position of deformation changes as the mining proceeds. It is impossible and impractical to trace the spatially varying deformation by GPS measurement, from which only the displacement of the observation point is detectable. InSAR, on the other hand, is effective in such cases because it can measure twodimensional deformation with high spatial resolution. PALSAR can detect and measure deformation of vegetated areas as it uses L-band microwave. For future studies, we will continue to observe land deformation of this area periodically by using PALSAR and RADARSAT. Acknowledgments The information on coal mining tunnels was provided by Turkish Hardcoal Enterprise (TTK). The authors would like to thank TTK for providing these precious data. This research work has been supported by the Earth Remote Sensing Data Analysis Center- ERSDAC Japan and Scientific Research Unit of Zonguldak Karaelmas University (ZKU). The authors wish to thank ERSDAC and ZKU for their supports. Furthermore, we sincerely thank to Mr. Tomonori Deguchi for SAR analyzes and important contributions. REFERENCES Deguchi T. (2005). Automatic InSAR processing and introduction of its application studies, Proceedings the 26th Asian Conference on Remote Sensing, Hanoi, Vietnam. Deguchi T., Kato M., Akcin H. and Kutoglu H. S. (2006). Automatic Processing of Interferometric SAR and accuracy of surface deformation measurement, SPIE Europe Remote Sensing, Stockholm, Sweden. Ge, L., Rizos C., Han S. and Zebker H. (2001). Mining subsidence monitoring using the combined InSAR and GPS approach, The 10th FIG International Symposium on Deformation Measurements, California USA. Nga A.H.,*, Changa H., Gea L., Rizosa C., Omurab M. (2008). Radar ınterferometry for ground subsıdence monıtorıng usıng alos PALSAR data, The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008, Commission VII, WG VII/2. New Energy and Industrial Technology Development Organization (NEDO) (1991). The report on the present state and future trend on the latest policy and exploration of coal resource in the coal-producing countries, part 2, (Turkey, Iran and Pakistan), Rodriguez E. and Martin J. M. (1992). Theory and design of Interferometric synthetic aperture radars, IEE proceedings F, vol.139, no.2: p Raucoules D., Maisons C., Carnec C., Le Mouelic S., King C., Hosford S. (2003). Monitoring Of Slow Ground Deformation By ERS Radar İnterferometry On The Vauvert Salt Mine TS 5D - Landslide and Subsidence Monitoring I Commission: 6 11/12

12 (France) Comparison With Ground-Based Measurement, Remote Sensing of Environment 88 (2003) Raucoules D., Colesanti C., Carnec C. (2007). Use Of SAR İnterferometry For Detecting And Assessing Ground Subsidence, C. R. Geoscience 339 (2007) URL 1: BIOGRAPHICAL NOTES Hakan Akcin, Assistant Professor in Department of Geodesy and Photogrammetry Engineering at of Zonguldak Karaelmas University, Turkey. Hakan S. Kutoglu, Associate Professor in Department of Geodesy and Photogrammetry Engineering at of Zonguldak Karaelmas University, Turkey. TS 5D - Landslide and Subsidence Monitoring I Commission: 6 12/12