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The engineering behavior of nonplastic silts is more difficult to characterize than is the behavior of clay or sand. Especially, behavior of silty soils is important in view of the seismicity of several regions of alluvial deposits in the world, such as the United States, China, and Turkey. In several hazards substantial ground deformation, reduced bearing capacity, and liquefaction of silty soils have been attributed to excess pore pressure generation during dynamic loading. In this paper, an experimental study of the pore water pressure generation of silty soils was conducted by cyclic triaxial tests on samples of reconstituted soils by the slurry deposition method. In all tests silty samples which have different clay percentages were studied under different cyclic stress ratios. The results have showed that in soils having clay content equal to and less than 10%, the excess pore pressure ratio buildup was quicker with an increase in different cyclic stress ratios. When fine and clay content increases, excess pore water pressure decreases constant cyclic stress ratio in nonplastic silty soils. In addition, the applicability of the used criteria for the assessment of liquefaction susceptibility of fine grained soils is examined using laboratory test results.

Arazideki zeminlerin gerilme koşulları incelendiğinde, zeminlerin pek çok durumda anizotropik gerilme şartlarında olduğu görülmektedir. Bu zeminler, herhangi bir ilave yükleme olmasa dahi kayma gerilmesine maruz durumdadırlar. Günümüzde arazideki gerilme şartlarına bakılmaksızın, maliyet, zaman ve kolaylık gibi gerekçelerden dolayı üç eksenli basınç deneyleri izotropik gerilmeler altında ve başlangıç kayma gerilmesinin olmadığı numuneler üzerinde gerçekleştirilmektedir. Bu nedenle, zeminlerin drenajsız koşullardaki davranışı üzerinde başlangıç kayma gerilmesi varlığının etkisi belirlenmesi gereken önemli bir konudur. Bu çalışmada, laboratuvarda bulamaç çamuru konsolidasyon yöntemi ile hazırlanmış olan normal konsolide kaolin kilinin, farklı başlangıç kayma gerilmeleri ve ortalama efektif gerilmeler altındaki drenajsız davranışı üç eksenli basınç deneyleri kullanılarak incelenmiştir. Deney sonuçları, başlangıç kayma gerilmesindeki artışın, drenajsız kayma mukavemetini ve aşırı boşluk suyu basıncı oluşumunu önemli ölçüde etkileyebileceğini göstermektedir. Çalışma sonunda, izotropik koşullarda gerçekleştirilen üç eksenli basınç deneylerinden elde edilen drenajsız kayma mukavemeti kullanılarak, başlangıç kayma gerilmesine maruz kil zeminlerin drenajsız kayma mukavemetini belirlemeye yönelik olarak bir düzeltme faktörü önerilmiştir.

In this study, dynamic behaviours of a structure group with shallow foundations have been investigated using 2D finite element methods. In the first stage, the structures were subjected to an earthquake in E-W direction (x-x); in the second stage, the structures were subjected to the same earthquake in N-S direction (y-y). Considering different number of floors in the structure group, the maximum displacement value in the N-S direction was 0.55 m, obtained at the top of the 5-storey building. In a building with a same floor number, when the foundation width in increased by two times, lower horizontal displacement values are obtained. When the conditions are compared in which the structure group is subjected to earthquake in both directions; the displacement values obtained in the N-S direction are reduced by 50% compared to the displacement values obtained in the E-W direction. The direction of an earthquake is one of an important parameters in structural design in the earthquake vulnerable regions. The study area is located within a fault zone of a E-W slip direction. Therefore, dynamic analysis shows that the buildings with E-W directions were less vulnerable than buildings with the same structural characteristics in N-S directions.