Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Research Of The Change In The Clay Structures Durıng Consolıdatıon

Behaviour of the clayey materials is one of the important research subjects of Geotechnical Engineering. Classical way of defining engineering behaviour of the clays is based on the research of stress-deformation relations. Methods used up to now are usually based on calculating the deformations resulted from the stresses, namely stress based methods. However careful scientific studies show that there are some other factors that are effective on the stress deformation transformation and behaviours in micro levels are needed to be defined to analyze these effects.

In this thesis, twenty-five laboratory consolidation tests have been carried out. During these consolidation tests, which are applied at 175 different stress levels and observed at the durations varying between 1 minute and 72 hours, fabric structure of the clays ground formed after the consolidation behaviour is researched. Fabric structure formed after the consolidation tests are explanied with the photographs taken by using the ESEM analysis. In addition to these test results from the laboratory studies are presented.

Chapter 1 is the introduction. Chapter 2 is a literature survey on formation of clayey sediments, fabric and structure of clayey soils, aging and delayed compression of sediments and classification of clays. Also the methods and techniques that may be employed for determination of soil composition are presented.

Methodology of this experimental study is explained in Chapter 3. In this Chapter, the geology and soil profile of kaolin are presented. Also engineering properties of the clay that was used in this experimental study and test methods are presented in detail.

Chapter 4 deals with the results of laboratory tests and evaluation of these tests. In this chapter compression behavior of clay is defined by performing total twenty-five conventional and long term consolidation tests. Also, fabric study of undisturbed and unloaded clay and changes in fabric due to compression, under different consolidation pressure levels are investigated by means of ESEM analysis.

In the last chapter, conclusions of the research work obtained by experimental studies and ESEM analysis are presented.

The conclusions based on laboratory tests and ESEM analyses are summarized in the following paragraphs.

By the ESEM analysis it is observed that there are changes occuring in the structure of the clay ground depending on the pressure and consolidation time. As the application time of the pressure increases, it is observed that void ratio in the ground decreases and clay particles and minerals are aligned, namely changed their position as aligning vertically to the surface of the pressure. Because of the arc-formed structures, applied stresses are not transmitted everywhere in the samples. So that alignment is not observed everywhere. At the same time it is observed that as the duration time of the samples under stress increases, alignment vertical to the stress surface increases. Also it is observed that as the amount of stress increases, change in the structure of the clay shifts from elastic type of deformation to plastic type of deformation.