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STUDYING THE EFFECTS OF LEACHING ON TREATED GYPSUM-RICH SOIL

Ali Nasir Ibrahim

Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة
ISSN: 25200917 Year: 2019 Volume: 23 Issue: 1 Pages: 162-173
Publisher: Al-Mustansyriah University الجامعة المستنصرية

Abstract

This wok focus on improving the permeability properties of gypseous soil by mixing the soil with three types of stabilizer materials, which are silicone oil, sodium silicate and bentonite. Four soil samples were prepared, first untreated soil, second mixture of 70% gepseous soil and 30% silicone oil, third mixture of 70% gypseous soil and 30% sodium silicate and forth mixture of 70 % gypseous soil and 30% bentonite . The leaching tests were conducted for all prepared soil using oedometer-permeability leaching device. The results show that the coefficient of permeability decreases with increasing of time, dissolved gypsum and leaching strain, this may attribute to the fact that the stabilizer materials fill the pores that produce from gypsum dissolution after leaching, thus in turn reduce the water fluctuate in the soil which minimize the gypsum dissolution.On the other hand the stabilizer materials work as an impermeable layer to prevent direct contact of water and gypsum particles. Where the leaching strain increases with increasing of dissolved gypsum as the leaching process continues. This behavior may be attributed to the continuous dissolution of gypsum that causes correspond a continuous settlement. Also leaching strain increases with void ratio increasing as the leaching process continue, where the continuous gypsum dissolution leads to increase in void ratio due to presence of pores. The treated gypseoussoil has less void ratio in comparison to untreated soil, due to reduction in gypsum dissolution for treated gypseous soil and thus in turn reduces leaching strain. Sodium silicate shows high efficiency in reducing coefficient of permeability compared to silicone oil and bentonite.

Keywords

Leaching --- stabilizer materials --- gypsum-rich soil --- permeability.