Suya Doygun Kohezyonsuz Sonsuz Şevlerin Sismik Stabilite ve Deformasyon Durumlarının Efektif Gerilme Tabanlı Sayısal Analizi

Öz

Şevlerin sismik yükler altındaki göçme ve deformasyon durumları çeşitli mekanizmalar tarafından kontrol edilmektedir. Temel mekanizmalar, statik yükleme koşullarına bağlı olan başlangıç gerilme durumu, sismik kayma gerilmelerine bağlı olan atalet etkileri ve aşırı boşluksuyu basıncı gelişimine parallel olarak meydana gelen kayma dayanımı ve rijitlik kayıplarıdır. Sismik yükleme sırasında, statik ve sismik kayma gerilmelerinin kombinasyonundan oluşan gerilme durumunun mevcut kayma dayanımını aşması durumunda kalıcı deformasyonlar meydana gelmektedir. Öte yandan, sismik yükleme sırasında meydana gelen kayma dayanımı ve rijitlik kayıpları ise, granüler zeminlerde daha çok zemin deformasyonuna bağlı olarak gelişen aşırı boşluksuyu basıncı artışlarından, kohezyonlu zeminlerde ise zeminin yumuşamasından kaynaklanmaktadır. Bu çalışma kapsamında, efektif gerilme tabanlı sismik tepki analizleri ve kayma dayanımı kayıplarını dikkate alan Modifiye Newmark yöntemi birlikte kullanılarak yukarıda sıralanan faktörlerin suya doygun kohezyonsuz sonsuz şevlerin sismik stabilite ve deformasyon durumlarında meydana gelebilecek etkiler sayısal olarak ele alınmıştır.

Anahtar Kelimeler

• efektif gerilme tabanlı analiz
• sismik şev stabilitesi
• atalet etkileri ve kayma dayanımı kaybı etkileri
• aşırı boşluksuyu basıncı
• kritik sismik ivme katsayısı
• kalıcı yerdeğiştirmeler

Effective Stress Based Assessment of Seismic Stability Condition and Permanent Displacements of Saturated Cohesionless Infinite Slopes

Abstract

Seismic failure and deformation behavior of slopes is dominated by various mechanisms. Initial stress state due to static loading conditions in addition to inertial and weakening effects due to seismic exci-tation are among the main mechanisms. Inertial effects arise from seismic shear stresses. When they add on to initial static shear stresses, combined shear stresses may exceed available shear strength temporarily and lead to permanent displacements. Weakening effects, on the other hand, arise from straining of the soil mass giving rise to excess po-rewater pressure generation in cohesionless soils and cyclic degradation effects in cohesive soils which result in reduction in the available shear strength and stiffness. In the context of this paper, effective stress based seismic response analysis and Modified Newmark Method for shear strength re-duction effects are used in coordination with each other in order to investigate the effect of mentioned factors on seismic stability and deformation beha-vior of saturated cohesionless infinite slopes.

Keywords

• effective stress based analysis
• seismic slope stability
• inertial and weakening effects
• excess porewater pressure
• critical seismic acceleration coefficient
• permanent displacements

Kaynakça

1. Bandini, V., Biondi, G., Cascone, E., Rampello, S. (2015) A GLE-Based Model for Seismic Displacement Analysis of Slopes Including Strength Degradation and Geometry Rearrangement, Soil Dynamics and Earthquake Engineering, Vol. 71. Pp.128-142.
2. Biondi,G., Condorelli, A., Cascone, E., Mussumeci, G. (2004) Earthquake triggered landslide Hazards in the Catania Area, Management Information Systems, Vol.9, pp.115-130.
3. Biondi,G., Cascone, E., Maugeri, M. (2001) Seismic Response of Submerged Cohesionless Slopes, 4th. International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, March 26-31, Missouri University of Science and Technology.
4. Biondi G., Cascone,E., Maugeri,M., Motta,E. (2000) Pore Pressure Effect on Seismic Response of Slopes, 12th. World Conference on Earthquake Engineering, Auckland.
5. Biondi, G Cascone, E., Maugeri, M. (2002) Flow and Deformation Failure of Sandy Slopes, Soil Dynamics and Earthquake Engineering, Vol.22, pp.1103-1114
6. Biondi, G Cascone, E., Rampello, S. (2007) Performance- Based Pseudo-Static Analysis of Slopes, 4ICEGE, 4th International Conference on Earthquake Geotechnical Engineering, Greece.
7. Biondi, G., Di Filippo, G., Maugeri, M. (2007) Effect of Earthquake-Induced Porewater Pressure in Clay Slopes, 4ICEGE, 4th International Conference on Earthquake Geotechnical Engineering, Greece.
8. Biondi,G., Cascone, E., Maugeri, M. (2008) Evaluation of Pseudo-Static Coefficients according to Performance Based Criteria, Seismic Engineering Conference Commemorating the 1908 Messina and Reggio Calabria Earthquake (edt. by Santini Moraci), AIP, pp.501-508.

9. Biondi, G, Maugeri, M. (2006) A Modified Newmark Type Analysis According to EC-8 Requirements for Seismic Stability Analysis of Natural Slopes, ETC-12 Geotechnical Evaluation and Application of the Seismic Eurocode EC8 2003-2006, Ed. By Boucovolas, G., General Report, Proceedings of the Athens Workshop, pp.151-176.
10. Brabhaharan, P., Mason, D., Gkeli, E. (2018) Seismic Design and Performance of High Cut Slopes, NZ Transport Agency Research Report 613, Contracted Research Organisation – Opus International Consultants Ltd. P.149.
11. Bray, J.D (2007) Simplified Seismic Slope Displacement Procedures, Earthquake Geotechnical Engineering (Eds. K.D. Pitilakis), pp.327-353.
12. Carlton, B., Kaynia, A.M. (2019) Empirical Model for Seismically Induced Shear Strains in Slopes, Earthquake Geotechnical Engineering for Protection and Development of Environment and Constructions, Silvestri and Moraci (Eds.), Rome, Italy. Pp.1629-1637.
13. Cui, Y., Liu, A., Xu, C., Zheng, J. (2019) A Modified Newmark Method for Calculating Permanent Displacement of Seismic Slope Considering Dynamic Critical Acceleration, Advances in Civil Engineering, Vol.3., pp. 1-10.
14. Dey, R., Hawlader, B., Philips, R., Soga, K. (2011) Modelling of Earthquake Induced Pore Pressure and Submarine Slope Stability Analysis, Pan-Am CGS Geotechnical Conference.
15. Elgamal, A., Dobry, R., Parra, E., Yang, Z. (1998). Soil Dilation and Shear Deformations During Liquefaction. Proceedings of the 4th. International Conference On Case Histories in Geotechnical Engineering. Missauri University of Science and Technology.1238-1259.
16. Elgamal A., Yang, Z., Parra, E., Ragheb, A. (2003). Modelling of Cyclic Mobility in Saturated Cohesionless Soils. International Journal of Plasticity. 19, 883-905. Elgamal, A. (2014). Site Liquefaction. Stress-Strain Response. Stress-Strain Models. Site Response. Lateral Deformation. Course Notes. Universidad Naciaonal de SanJuan, Argentina.
17. Filippo, G.D., Cascone, E (2019) Influence of Earthquake-Induced Porewater Pressure on the Seismic Stability of Cohesive Slopes, Earthquake Geotechnical Engineering for the Protection and Development of Environment and Constructions, Eds. Francesco Silvestri and Nicola Moraci, Proceedings of the VII ICEGE 7th. International Conference On Earthquake Geotechnical Engineering, Rome, Italy, 17-20 June, 2019, pp??
18. Ingegneri, S., Biondi, G., Cascone, E., Filippo, G.D. (2019) Influence of Cyclic Strength Degredation on a Newmark Type Analysis, Earthquake Geotechnical Engineering for the Protection and Development of Environment and Constructions, Eds. Francesco Silvestri and Nicola Moraci, Proceedings of the VII ICEGE 7th. International Conference On Earthquake Geotechnical Engineering, Rome, Italy, 17-20 June, 2019, p.2996-3004.
19. Jafarian, Y., Lashgari, A. (2017) Seismic Sliding Analysis of Sandy Slopes Subjected to Porewater Pressure Build Up, ASCE International Journal of Geomechanics, vol.17, Issue 11.
20. Jıa, J. (2018) Slope Stability Due to Seismic Loading (Chp. 8), Soil Dynamics and Foundation Modelling - Offshore and Earthquake Engineering, Springer, Aker solution, Bergen, Norway.
21. Khosravi, M., Khosravi, A. (2013) Stability Analysis of Seismically Loaded Slopes Using Finite Element Techniques, ASCE Geocongress 2013, Geotechnical Special Publication, p.1310-1319.
22. Kramer S. L. (1996) Geotechnical Eartquake Engineering. Prentice-Hall, Inc., Upper Saddle River, NewJersey 07458.
23. Karray, M., Hussien, M.,Delisle, M., Ledoux, C. (2018) Framework to Assess Pseudo-Static Approach for Seismic Stability of Clayey Slopes, Canadian Geotechnical Journal, Vol.55., No.12, pp.1-17.
24. Magistris, F.S. (2011) Beyond EC8: The New Italian Seismic Code, Geofizika, Vol.28. p.65-82.
25. Mendez, B., Taştan, E.O., Gutierrez, J. (2017) Performance Based Slope Stability Analysis and the Pseudo-Static Factor of Safety, Geotechnical Frontiers 2017, Orlando, Florida, p.1-10.
26. Parra, E. (1996). Numerical modeling of liquefaction and lateral ground deformation including cyclic mobility and dilation response in soil systems. Ph.D. thesis. Troy, N.Y.: Dept. of Civil Engineering, Rensselaer Polytechnic Institute.
27. Rathje, E.M., Antonakos, G. (2011) A Unified Model for Predicting Earthquake-Induced Sliding Displacements of Rigid and Flexible Slopes, Engineering Geology, Vol.122, pp.51-60.
28. Rampello, S., Callisto, L., Fargnoli, P. (2010) Evaluation of Slope Performance Under Earthquake Loading Conditions, Rivista Italiana Di Geotechnica, pp.29-41. NCHRP Report No. 611 Seismic Analysis and Design of Retaining Walls, Buried Structures, Slopes and Embankments, Transportation Research Board, p.148. WSDOT Washington State Department of Transportation Geotechnical Design Manual, Chapter 6 Seismic Design, p. 80.(2019)