Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Cyclic Swell – Shrink Behaviour of İstanbul Gürpınar Clay

Clayey levels of Gurpinar formation which exists under one of the major residential areas of İstanbul around the Küçükçekmece and Büyükçekmece Lakes, is named as Gurpinar clay. Despite of its swelling and landslide problems, there is not a comprehensive research on the swelling potential and cyclic swell-shrink behaviour. To reveal these properties and behaviour, 5 different samples of Gürpınar clay were taken from 4 different regions. The cyclic swell –shrink experiments with full drying - full wetting were carried out for totally 14 undisturbed and reconstituted specimens. Additionally, in order to define the swell-shrink potential, some other tests were done. To recognize the effect of cyclic swell-shrink on the structure of clay, the electron microscope analysis, XRD analysis, index tests and consolidation tests are carried out on the natural and cyclic swelled-shrinked samples. The swelling potential and the swelling pressure changes of Gurpinar clays exposed to cyclic swell – shrink, show similarities with other clays in the literature. In this research, the reasons of different results for the cyclic swelling-shrinkage behaviour are explained by mineralogy, structure and origin (orientation and bond stability) of the clay. Additionally, cyclic swelling index (CSI) and cyclic swelling pressure index (CSPI) parameters are defined. Very high correlation is found for these two parameters with the ratio of maximum saturated water content (w_s) to natural water content (w_o) which can be readily found. With these developed relations, it is possible to obtain the final swelling potential and swelling pressure of Gurpinar clay when expose to cyclic swell-shrink.