Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Chemical Stabilization of Expansive Soils

Swelling soils exhibit increase in volume when they their water content increases. It has been reported that swelling soils cause damage totaling to an amount of 2-3 billion dollars, which is more than that caused by other catastrophes. Swelling solis cause problems also in Turkey. Chemical stabilization is one of the most frequently used methods used in stabilization of expansive soils. These chemicals are lime, cement, fly ash, etc. These chemicals decrease or eliminate swelling potential and increase strength in the long term.

In this study, lime stabilization of an expansive soil is studied. The soil studied is a potentially high expansive potential soil form Istanbul-Esenyurt region. The samples were prepared taking into the field conditions where the soil may or may not be adequately pulverized, or prewetted or not prewetted. Effect of lime and field construction procedures on different geotechnical properties is investigated. The samples were also investigated in terms of microstructure. The investigations included ESEM analyses, mercury intrusion porosimetry analyses and chemical content analyses.

Lime addition changed the Atterberg Limits of the studied soil and this changed the soil class. The workability of the soil also increased as a result of compaction characteristics. The experiments showed that, %3 lime stabilization revealed short terms reactions, but was not enough to provide enough pozzolanic reactions and therefore did not cause considerable changed in unconfined strength values. %6 and %9 lime addition increased the unconfined compression strength values in a considerable amount. All lime contents caused increases the Elasticity Modulus values.

The effect of prewetting did not have a pronounced effect on unconfined strength and elasticity modulus values. High quality pulverization resulted in higher unconfined compression and Elasticity Modulus values. The lowest modulus values were obtained in samples which were prepared by very low quality pulverized soil.

Unstabilized clay showed a very high swelling potential. Swelling pressures ranged between 300-500 kPa. There was no considerable relationship between samples preparation method and swelling values. %3, %6 and %9 lime eliminated the swelling potential and the swelling pressures. Pressures greater than the yield pressure for lime stabilized soils resulted in destruction of the cementation formed due to lime addition.

Mercury intrusion porosimetry tests revealed that lime increased the porosity values. It is anticipated that, during curing, intraparticular pores are first to be filled with cementation. Increase in lime content caused increases in all volumes corresponding to different pore readius values. Soils prepared with very low quality pulverization resulted in higher volume values for a alrge range of pore radius values. ESEM analyses showed that lime additon changed the fabric from a continous one to a porous one. The analyses also revealed formation of new minerals in the stabilizaed samples

The results of the study show that lime stabilization is an appropriate way of improving the studied soil. The level of improvement is closely related to the quality of pulverization. It is obvious that, in field applications, it is essential to obtain a high quality of pulverization. Otherwise, the laboratory obtained stabilization performances will not be achieved in the field.

BAŞTAN Ömer Ali
Danışman : Doç.Dr.Adnan Çolak

Anabilim Dalı : İnşaat Mühendisliği

Mezuniyet Yılı : 2008

Tez Savunma Jürisi : Doç.Dr.Adnan Çolak

Prof.Dr.Süleyman Dalgıç

Prof.Dr.Ekrem Manisalı

Yrd.DoçDr.Turgay Coşgun

Yrd.DoçDr.Ahmet Erhan Bakırcı