Susceptibility mapping for sinkhole occurrence by GIS and SSI methods: A case study in Afsin-Elbistan coal basin

Abstract

The major structural defects that cause the displacement in rock are discontinuities (fracture-joint-fault) and karstic cavities. Depending on the position and geometry of the karstic cavities, sinkholes occur both within the bedrock and in the cover layers. Occurance of sinkholes primarily depends on existence of carbonate rocks containing sub-surface karstic cavities and loose and weak cover layers. Following the landslides occured in 2011, it was planned to reduce the hydraulic head of the karstic aquifer which lies at the bottom of the coal-bearing layers in order to restart the mining activity in Afşin-Elbistan Coal Basin. For this purpose, dewatering wells were drilled in January 2015. Two weeks after the drilling, the first sinkhole occured at the southwestern edge of the basin and during the following six months four other sinkholes occured close to the first one. The geological, hydrological, hydrogeological and geo-mechanical models of the basin has been composed in order to understand the mechanism of sinkhole occurence in the Afşin-Elbistan Coal Basin. Thematic maps showing the spatial distribution of parameters which determine the formation of sinkholes were obtained by using a Geographic Information System (GIS) based analysis method. Analytical Hierarchy Process (AHP) approach, which is one of the multi-criteria decision-making analyzes, has been adopted in determining the impact and weight coefficients of each effective parameter which plays a role in occurance of the sinkholes. The Sinkhole Susceptibility Index (SSI) was calculated by using all parameters which were classified and weighted. The SSI refers to the susceptibility of sinkhole occurance. The higher value of the SSI means that the risk of potential occurrence of a sinkhole is high. Calculated SSI in the study area ranges from 9 to 110 and the higher values were obtained for the area corresponding to the margin of the basin where the sinkholes occurred.

Keywords

• Karst
• Coal site
• Sinkhole susceptibility Index
• Dewatering
• Groundwater

References

1. [1] Newton JG. “Sinkhole resulting from groundwater withdrawals an carbonate terranesan overview”. Geological Society of America, Reviews in Engineering Geology, 6, 195-202, 1984.
2. [2] Bayarı CS, Pekkan A, Ozyurt NN. “Obruks, as giant collapse dolines caused by hypogenic karstification in central Anatolia, Turkey: Analysis of likely formation processes”. Hydrogeology Journal, 17, 327-345, 2009.
3. [3] Doğa U, Çiçek I. “Occurrence of cover-collapse sinkholes (cover-collapse dolines) in the May Dam reservoir area (Konya-Turkey)”. Cave and Karst Science, 29(3), 111-116, 2003.
4. [4] Doğan U, Yılmaz M. “Natural and induced sinkholes of the obruk plateau and Karapınar-Hotamis plain, Turkey”. Journal of Asian Earth Sciences, 40, 496-508, 2011.
5. [5] Yılmaz M. “Environmental problems caused by ground water level changes around Karapınar”, Ankara University Çevre Bilimleri Enstitüsü, 2(2), 145-163, 2010.
6. [6] Özdemir A. “Sinkhole susceptibility mapping using a frequency ratio method and GIS technology near Karapınar, Konya-Turkey”. World Multidisiplinary Earth Sciences Symposium, Procedia Earth and Planetary Science, 15, 502-506, 2015.
7. [7] Waltham T. “Sinkhole hazard case histories in karst terrains”. Quarterly Journal of Engineering Geology and Hydrogeology, 41(3), 291-300, 2008.
8. [8] Tharp TM. “Mechanics of formation of cover collapse sinkholes”. Engineering Geology, 52(1-2), 23-33, 1999.

9. [9] Goodings A. “Stability charts for predicting sinkholes in weakly cemented sand over karst limestone”. Engineering Geology, 65, 179-184, 2002.
10. [10] Augarde CE, Lyamin AV, Sloan SW. “Prediction of undrained sinkhole collapse”. Journal of Geotechnical and Geoenvironmental Engineering, 129(3), 197-205, 2003.
11. [11] Rawal K, Hu LB, Wang ZM. “Numerical investigation of the geomechanics of sinkhole formation and subsidence”. Geotechnical Frontiers, Orlando Florida, U.S, 12-13 March, 2017.
12. [12] İstanbul Teknik Üniversitesi. Afşin Elbistan Kömür Havzasında Güncel Obruk Oluşumlarının Yerbilimsel Yöntemlerle Araştırılması. İTÜ Maden Fakültesi Vakfı, İstanbul, Türkiye, 2017. (Yayınlanmamış).
13. [13] Mahmutoğlu Y, Karagüzel R, Şans G, Erdoğan M, Bozkurtoğlu E, Akyüz HS, İşseven T, Taştekin C, Ata E. “Karst susuzlaştırmasının obruk oluşumuna etkisi: Afşin-Elbistan linyit sahası örneği”. MÜHJEO’2017, Adana, Türkiye, 12-14 Ekim 2017.
14. [14] Mahmutoğlu Y, Karagüzel R, Şans G, Erdoğan Topçuoğlu M. “Sinkholes induced by dewatering in an open pit mine case study from a coal basin in Eastern Turkey”. Rock Dynamic Summit in Okinawa, Japan, 7-11 May 2019.
15. [15] Saaty TL. The Analytic Hierarchy Process. New York, USA, McGraw-Hill, 1980.
16. [16] Montan Bildungs- und Entwicklungsgesellschaft mbH. “Çöllolar Open Cast Mine Afsin Elbistan Coal Basin, Phase II: Detail Planning Çöllolar Open Cast Mine Subproject 2: Hydrogeological Model and Dewatering Concept”. 103, 2008.
17. [17] Maden Teknik Arama Genel Müdürlüğü “Afşin-Elbistan Kömür Havzası HB ve HD Sektörlerinin Jeoloji, Rezerv ve Hidrojeoloji Raporu”. Ankara, Türkiye, 2009, 2015.
18. [18] Montan Bildungs- und Entwicklungsgesellschaft mbH. “Consultancy and Engineering Services for Mine Operation in Çöllolar Open Cast Mine (Afşin Elbistan Coal Basin), Phase V: Mine Plan fort he Restart of Coal Mining & Status Report 06/2012, Subprojects: Geological Modelling/Hydrogeology/Dewatering/Geotechnics and Mine Planning”. 160, 2012.