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

Abstract

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.

Keywords

• 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

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