Swelling soil is one of the most problem and disaster sources which is facing building construction, pavements, roads, and railways.
The phenomena of expansive soil occurs when it is exposed to moisture content variation, because of their physical-mechanical and chemical characteristics, causing large volume changes which leading to cracking and break down of engineering projects .
The research aims to study swelling soil in three location of Duhok city, undisturbed samples were taken from three different location, (kayar city, Tanahi, and Masike) the soil samples were taken by rotary drilling machine without using water from depth ranges between (2.0-2.5) m.
Physical- mechanical tests were achieved at Duhok constructional laboratory.
From the results obtained shows the swelling pressure increases as the index of plasticity increases liquid limit, percentage of clay particles and index of compressibility.
To solve this problem , many methods suggested , such as replacement or improvement of soil , and protection of soil from moisture .