Ön Yüzü Geomembran Kaplı Yüksek Bir KayaDolgu Barajın Deprem ve Geomembranda Yırtık Olması Durumunda Performansının Değerlendirilmesi

Yıl 2019, Sayı: 16, 460 - 470, 31.08.2019

Uğur Şafak Çavuş , Murat Kilit

https://doi.org/10.31590/ejosat.549123

Öz

Bu makale sızmaya
karşı ön yüzü geomembran ile kaplı yüksek bir kaya dolgu barajın deprem olması
veya geomembran kaplamada olası bir yırtık olması nedeniyle baraj gövdesinde
sızma oluşması durumlarına karşılık stabilite ve sızma analizlerine dayalı
barajın performasını ve güvenliğini değerlendirmektedir. Bu nedenle, sonlu
elemanlar zamana bağlı değişen sızma analizi ve şev stabilite analizi baraj
gövdesindeki kritik kayma yüzeylerini ve güvenlik değerlerini belirlemek için
gerçekleştirilmiştir. İlk olarak baraj gövdesindeki suyun sızma yolları ve
kayma yüzeylerine etki eden boşluk suyu basınçları zamanla değişen akım hali
için numerik sızma analizleri yapılarak belirlenmiştir. Şev stabilitesi
açısından kritik durumun, geoemembrandaki yırtığın rezervuar tamamen dolu halde
iken nss seviyesinde oluştuğu tespit edilmiştir. Çünkü bu durumda, baraj
gövdesinde hidrolik su yüksekliği ve buna bağlı kaya dolguda su sızma
basınçları maksimum olmaktadır. Analiz sonuçları göstermiştir ki eğer barajın bulunduğu
bölgeye kuvvetli bir deprem etkirse, barajın memba ve mansap şevleri, yüksek
güvenlik faktörleri ile kaymaya karşı yeterince güvenli bulunmaktadır. Ayrıca,
eğer geomembrane kaplamada bir hasar neticesinde yırtık oluşursa, barajın
mansap şevi 2.25 yatay 1 düşey eğimiyle yine yeterince stabil olacağı
görülmüştür. Fakat hem kaya dolgu hem de baraj gövdesi altındaki kayaç
geçirimli olduğundan, geomembranda bir sızma olursa barajın temelinden sızan
suların basıncının sönümlendirilmesi ve güvenle barajın topuğundan
uzaklaştırılması amacıyla baraj mansap topuğunda dren veya basınç
sönümlendirici bir kuyu tasarlanması tavsiye edilmektedir.

Anahtar Kelimeler

Kaya Dolgu Baraj, Geomembrane Kaplama, Şev Stabilitesi, Zamanla Değişen Akım

Performance Evaluation of A High Geomembrane Faced Rockfill Dam In Case of Liner Rupture and Earthquake Risks

Öz

This paper presents stability and seepage evaluation of a high rockfill
dam with a geomembrane seepage barrier by considering scenarios of a possible
occurrence of a large earthquake due to the active faults in the region and
also a seepage flow in the dam due to a possible rupture of the geomembrane
liner. For this purpose, finite element transient seepage and pseudo static
slope stability analyses were both carried out together to assess the critical
potential failure surfaces and safety factors of the rockfill slopes.  Therefore, pore water pressures on the
failure surfaces were first calculated using the time varying (transient)
numerical seepage analyses method which is essentially important to determine
the time dependent variations of seepage paths and water pressures within the
rockfill as well. In the analyses, it was determined that the most critical
slope failure case is when a geomembrane liner tears at the time of the highest
reservoir water elevation since the hydraulic head is maximum and causes the
largest seepage pressure in the rockfill there. 
Analyses showed that if a strong earthquake struck the region, both the
upstream and downstream slopes are safe with sufficiently high safety factors.
In addition, in case of a possible tear and leakage on the geomembrane liner,
the dam will also withstand well with 2.25 horizontal to 1 vertical slopes.
However, it is recommended that constructing a downstream toe drain or a relief
well will provide an additional safety measure against any heave occurrence or
instability of the rockfill since the embankment and bedrock foundation are
pervious causing high seepage pressures at the downstream toe of the dam.  

Anahtar Kelimeler

Rockfill Dam, Geomembrane Liner, Slope Stability, Transient Flow

Kaynakça

• Koerner , R. M., & Wilkes, J. A. (2012). 2010 ICOLD Bulletin on Geomembrane Sealing Systems for Dams. Geosynthetics.
• ICOLD. (2010). Geomembrane Sealing Systems for Dams - Design Principles and Return of Experience.Bulletin 135. France.
• ICOLD. (2011). Small Dams-design, Surveillance and Rehabilitation. International Commission on Large Dams, Bulletin 143. France.
• Bhowmik, R., Shahu, J., & Datta, M. (2017). Failure analysis of a geomembrane lined reservoir embankment. Geotextiles and Geomembranes, vol. 46, p. 52-65.
• Poulain, D., Peyras, L., & Meriaux, P. (2011). Feedback and guidelines for geomembrane lining systems of mountain reservoirs in France. Geotextiles and Geomembranes, Vol. 29, p. 415-424.
• Mendoza, C., Gisbert, A., Izquierdo, A., & Bovea, M. (2009). Safety factor nomograms for homogeneous earth dams less than ten meters high. Engineering Geology, vol. 105, p. 231-238.
• Tolooiyana, A., Abustana, I., Selamata, M., & Ghaffari, S. (2009). A comprehensive method for analyzing the effect of geotextile layers on embankment stability. Geotextiles and Geomembranes, Vol.27, p. 399-405.
• Briancon, L., H., G., & D., P. (2002). Slope stability of lining systems- experimental modelling of friction at geosynthetic interface. Geotextiles and geomembranes, Vol. 20, P. 147-172.
• Earth, G. (2019). 3 3, 2019 tarihinde Google Earth: http://www. google.com.tr/int/tr/earth adresinden alındı
• Erlingsson, S., & Hauksson, D. R. (2009). Analysis of a geomembrane face rockfill dam during earthquake loading. Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering, p. 1678-1681.
• Jones, D. R., & Dixon, N. (2003). Stability of Landfill Lining Systems: Report No. 1. R&D Technical Report P1-385/TR1. Research Contractor: Golder Associates (UK) Ltd. In conjunction with Loughborough University Consultants Ltd.
• MTA-Turkey. (2016). Dinar active fault map. http://www.mta.gov.tr/v2.0/default.php?id=yeni_diri_fay_haritalari: http://www.mta.gov.tr/v2.0/default.php?id=yeni_diri_fay_haritalari adresinden alınmıştır
• Gülkan, P., & Kalkan, E. (2002). Attenuation modeling of recent earthquakes in Turkey. Journal of Seismology, Vol. 6, p. 397-409.
• Giroud, J. a. (1989). Leakage through liners constructed with geomembranes – Parts I and II. Geotextiles and Geomembranes, 8(1-2), p. 27-67 and 71-111.
• Giroud, J. P. (1997). Equations for calculating the rate of liquid migration through composite liners due to geomembrane defects. Geosynthetics International, Vol. 4(3-4), p. 335-348.
• Foose, G. J., Benson, C. H., & Edil, T. B. (2001). Predicting leakage through composite landfill liners. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 127(6), p. 510-520.
• Touze-Foltz, N., & Giroud, J. P. (2005). Empirical equations for calculating the rate of liquid flow through composite liners due to large circular defects in the geomembrane. Geosynthetics International, Vol.12 No.1, p. 205-207.
• Girard, H., Fischer, S., & Alonso, E. (1990). Problems of friction posed by the use of geomembranes on dam slopes-examples and measurements. Geotext. Geomembranes, Vol. 9, p. 129-143.
• Wu, W., Wang, X., & Aschauer, F. (2008). Investigation on failure of a geosynthetic lined reservoir. Geotexit and Geomembranes, Vol. 26, p.363-370.
• Moraci, N., Cardile, G., Gioffrè, D., Mandaglio, M. C., Calvarano, L. S., & Carbone, L. (2014). Soil geosynthetic interaction: Design parameters from experimental and theoretical analysis. Transportation. Infrastructure. Geotechnology., p. 165-227.
• Weber, C. T. (2008). Leakage through defects in geomembrane liners under high hydraulic heads. Texas: The University of Texas at Austin.
• Weber, C. T., & Zornberg, J. (2008). Numerical analysis of leakage through geomembrane lining systems for dams. The First Pan American Geosynthetics Conference & Exhibition. Cancun, Mexico.
• SLIDE. (2010-2016). Comprehensive slope stability analysis software. Rocscience Inc., 39 University Ave Ste 780 Toronto, Ontario M5G 1Y8.
• Leps, T. (1970). Review of the shearing strength of rockfill. J. of Soil Mech. and Found. Div., Vol. 96(SM4), p. 1159-1170.
• Barton, N., & Kjærnsli, B. (1981). Shear strength of rockfill. J. of the Geotech. Eng. Div., Vol. 107(GT7), p. 873-891.
• Marachi, N. D., Chan, C. K., & Seed, H. B. (1972). Evaluation of properties of rockfill materials. J. Soil Mech. Found. Div., Vol. 98(SM1), p. 95-114.
• Eurocode, 7. (2013, June 13-14). Geotechnical Design. Dublin.
• Bishop, A. W. (1955). The Use of the slip circle in the stability analysis of slope. Geotechnique, Vol. 5, P. 7-17.
• Charbeneau, R. J. (2000). Groundwater .hydraulics and pollutant transport. New Jersey: Prentice Hall.