ABSTRACT: While more than half the land surface of Iraq consists of deserts covered mainly with sand dunes, little research has taken place to study the characteristics and the behavior of dune soils. This paper directed toward studying the geotechnical properties of dune sands taken from Baiji city (northwest of Iraq). A vast laboratory testing program was carried out to achieve the purpose of this paper. The physical tests, chemical tests, X-ray diffraction analysis, permeability test, compaction characteristics, compressibility and collapsibility tests; and shear strength tests were included in this program. The results indicate that soil of Baiji sand dune exhibits prefer engineering properties according to their state. As such, this soil is considered suitable for use in geotechnical constructions. ABSTRAK: Walaupun lebih separuh daripada bumi Iraq terdiri daripada gurun yang dipenuhi dengan bukit-bukit pasir, tidak banyak penyelidikan dijalankan untuk mengkaji sifat-sifat dan ciri-ciri tanah pasir  tersebut. Kertas kerja ini menyelidik sifat geoteknikal bukit pasir yang diambil dari pekan Baiji (di bahagian barat utara Iraq).  Program penyelidikan makmal yang menyeluruh telah  dijalankan bagi mencapai objektif kajian ini. Ujian fizikal, ujian kimia, analisis belauan sinar-x, ujian kebolehtelapan, ciri pemadatan, faktor ketermampatan, ujian keruntuhan dan ujian kekuatan ricih diambilkira dalam program ini. Keputusan menunjukkan bahawa tanih bukit pasir Baiji mengutamakan ciri kejuruteraan berdasarkan keadaannya. Oleh itu, tanah ini dianggap sesuai untuk kegunaan pembinaan geoteknikal.

Characteristics of the expansive soil should be studied due to the effects and problems of this soil on the structures that build on it, also, its spread in large areas in the world. Some of these problems are the cracks and large damages on the structures due to the differential settlement of the soil. These problems occur due to the swelling and shrinkage characteristics of the soil when it is affected by changeable water content. The need for the stabilizers to overcome these problems appears due to a large amount of loses money caused by the expansive soil’s problems. This study used silica fume and metakaolin which considers stabilizer agents that used to treat the expansive soil. Silica fume is an industrial material obtained by condensation operation to the smoke that produced from the production process of the ferrosilicon metal. While metakaolin is a a pozzolanic material obtained from the burning of kaolin rock to (700-800) °C. The soil used in this study classified as CH soil. The treated samples were prepared by mixing the soil with (5%, 10%, and 15%) of the two additives. From the results, it was found that Atterberg limits were increased with the adding silica fume and decreased with Metakaolin. Specific gravity decreased with silica fume while it is increased with Metakaolin. The maximum dry unit weight decreased, and the optimum water content increased with silica fume and the opposite occur with metakaolin. The results showed that the swelling present improved with both additives.

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